CLAIM TO PRIORITY

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62/466,212, filed March 2, 2017, entitled "Motor Starting Circuits, and Motor Control Assemblies, and Grinder Pump Assemblies Employing Same", and U.S. Provisional Patent Application No. 62/468,203, filed March 7, 2017, entitled "Motor Starting Circuits, and Motor Control Assemblies, and Grinder Pump Assemblies Employing Same", the entire contents of which is hereby incorporated herein by reference.

FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to starting circuits for electric induction motors, and more particularly to motor starting circuits, motor control assemblies, and grinder pump assemblies employing same.

BACKGROUND

[0003] Grinder pumps are often used in low-pressure sewage systems for pumping sewage. A grinder pump includes a motor and a grinder mechanism for cutting or grinding solids or semisolid matter in the sewage being pumped.

Grinding solids and/or semisolid matter in the sewage allows the resulting particulate effluent to be transferred using a pump through a small diameter pipe without clogging.

[0004] Grinder pump systems are typically equipped with level sensors, a controller, and an alarm. When the sewage reaches a certain level in the tank, the motor of the grinder pump is automatically switched on and when the sewage in the tank falls below a certain level, the motor of the grinder pump is automatically turned off. If the level rises too high, typically another sensor activates an alarm. [0005] Grinder pumps typically include a capacitor-start/induction-run motor having two windings, a start winding and a run winding. During startup of the motor, a switching mechanism along with a start capacitor is employed to connect and disconnect the start winding to allow the motor to get up to speed.

SUMMARY

[0006] Shortcomings of the prior art are overcome and additional advantages are provided through the provision, in one embodiment, of a motor control assembly for use with a motor having a run winding and a start winding, and the motor being powered by an AC power supply. The motor control assembly includes, for example, a transformer having a primary winding through which AC power, from the AC power supply, to the run winding of the motor passes, an AC current sensing circuit operably connected to a secondary winding of the transformer for monitoring AC current to the motor, a solid state motor start circuit operably connected to the AC current sensing circuit for selectively controlling AC power to the start winding of the motor, and a start capacitor connectable in series between the solid state motor start circuit and the start winding of the motor. A DC relay controls the AC power to the run winding and the start winding of the motor. A DC coil driver circuit is operable in response to the AC power to be supplied to the motor for supplying a DC current to the DC relay for selectively controlling the DC relay. An AC voltage monitoring circuit is operably connected to the AC power supply for monitoring AC voltage from the AC power supply. A coil driver inhibitor circuit is operably connected to the AC voltage monitoring circuit and to the DC coil driver circuit. The coil driver inhibitor circuit is operable to shunt the DC relay in response to the AC voltage.

[0007] In another embodiment, a motor control assembly for use with a motor having a run winding and a start winding in which the motor powered by an AC power supply, includes for example a solid state motor start circuit operable for selectively controlling AC power to the start winding of the motor, a start capacitor connectable in series between the solid state motor start circuit and the start winding of the motor, a DC relay for controlling the AC power to the run winding and the start winding of the motor, a DC coil driver circuit operable in response to the AC power to be supplied to the motor for supplying a DC current to the DC relay for selectively controlling the DC relay to permit AC power to be supplied to the run winding of the motor, an AC voltage monitoring circuit operably connected to the AC power supply for monitoring AC voltage from the AC power supply, and a coil driver inhibitor circuit operably connected to the AC voltage monitoring circuit and to the DC coil driver circuit. The coil driver inhibitor circuit operable to shunt the DC relay to remove AC power from the motor in response to the AC voltage.

[0008] In another embodiment, a method for controlling a motor having a run winding and a start winding is provided. The method includes, for example, providing DC power to control AC power to the run winding of the motor from an AC power supply, sensing the current of the AC power to the motor, connecting AC power through a start capacitor to the start winding of the motor based on the sensed current of the AC power to the motor, sensing AC voltage of the AC power supply, and inhibiting the DC power to shut down the AC power to the run winding of the motor based on the sensed AC voltage of the AC power supply.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The subject matter which is regarded as the disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. The disclosure, however, may best be understood by reference to the following detailed description of various embodiments and the accompanying drawings in which:

[0010] FIG. 1 is an elevational view, in part cross-section, of a grinder pump system according to an embodiment of the present disclosure;

[0011] FIG. 2 is an enlarged cross-sectional view of the grinder pump system of FIG. 1 ;

[0012] FIG. 3 is a block diagram of a portion of a prior art grinder pump system having a motor control assembly having a mechanical motor start switch;

[0013] FIG. 4 is a block diagram of a portion of a prior art grinder pump assembly having a motor control assembly having a mechanical motor start switch and an over/under wattage protection assembly; [0014] FIG. 5 is a block diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure having a motor control assembly having a solid state motor start circuit;

[0015] FIG. 6 is a block diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure having a motor control assembly having a solid state motor start circuit and a DC control switch;

[0016] FIG. 7 is a block diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure having a motor control assembly having a solid state motor start circuit, a DC control switch, an

overcurrent protection circuit, and a locked rotor protection circuit;

[0017] FIG. 8 is a schematic diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure;

[0018] FIG. 9 is a perspective view of the a motor control assembly according to an embodiment of the present disclosure; and

[0019] FIG. 10 is a flowchart of a method according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0020] The present disclosure and certain features, advantages, and details thereof, are explained more fully below with reference to the non-limiting

embodiments illustrated in the accompanying drawings. Descriptions of well-known materials, fabrication tools, processing techniques, etc., are omitted so as to not unnecessarily obscure the disclosure in detail. It should be understood, however, that the detailed description and the specific examples, while indicating

embodiments of the present disclosure, are given by way of illustration only, and are not by way of limitation. Various substitutions, modifications, additions and/or arrangements within the spirit and/or scope of the underlying concepts will be apparent to those skilled in the art from this disclosure. Reference is made below to the drawings, which are not drawn to scale for ease of understanding, wherein the same reference numbers used throughout different figures designate the same or similar components.

[0021] FIG. 1 illustrates a low-pressure grinder pump system 100 according to an embodiment of the present disclosure for collecting, grinding, and pumping wastewater or sewage. Grinder pump system 100 generally includes a tank 120 and a grinder pump assembly 130. Grinder pump system 100 is readily installable in the ground by connecting the system to a wastewater feed pipe 122, a wastewater discharge pipe 124, and an electrical power supply via an electrical cable 126. Cable 128 may be connected to an alarm panel 140. The system may also be connected to or include a vent.

[0022] With reference to FIG. 2, grinder pump assembly 130 may include a housing 42, a grinder mechanism 52, a pump assembly 54, an electric motor 56 such as an AC induction motor, and motor control assembly 200. Liquid level sensing assembly 70 includes a central portion 72, which defines a cavity 76 such as a sealed chamber, and switches 80 and 82 such as pressure switches. Motor 56 may be a motor having a start winding and a run winding. Both windings are energized when the motor is started as described in greater detail below. When the motor reaches a percentage of its rated full load speed, the start winding is disconnected. The AC induction motor may be a dual voltage motor that is operable on two different voltage levels. Dual voltage motors allow the same motor to be used with two different power line voltages and still maintain the motor characteristics. As the voltage goes down the amperage will go up in value but the horsepower (HP) and rotations per minute (RPM) will remain the same. For example, with a single phase motor there are two sets of main run winding that are connected in parallel for the low voltage (1 10V) and in series for the high voltage (240V).

[0023] For example, with liquid level sensing assembly 70 constructed with two point level switches, e.g., low-level/on-off switch 82 and high-level alarm switch 80, and with both switches in an open position, the pump would be off. With a closed contact in the low-level/on-off switch and an open contact in the alarm switch, a normal run condition exists and would require the pump to turn on and purge the wastewater in the tank until the contact of the low-level/on-off switch opens. The opening and closing of the low-level/on-off switch may be at different levels. For example, the low level pressure switch may change from an open contact to a closed contact at 8 inches of wastewater and reset back to the open position at 4 inches of wastewater.

[0024] Grinder mechanism 52 pulverizes solids or semisolid matter in the wastewater. Pump assembly 54 is attached to grinder mechanism 52 for pumping the ground wastewater through grinder pump assembly 130. AC induction motor 56 powers both grinder mechanism 52 and pump assembly 54. For example, a grinder mechanism may include a stationary outer ring and a rotating cutting blade, and a pump assembly may include a progressing cavity pump having a pump housing, a pump stator, and a pump rotor. In operation, wastewater is drawn into grinder mechanism 52, as illustrated by the curved arrows S in FIG. 2, for cutting or grinding of the solids or semisolid matter in the wastewater. The resulting processed particulate effluent passes through pump assembly 54, a pipe 43 (FIG. 1 ), and then through wastewater discharge pipe 124 (FIG. 1 ) to a remote location, e.g., to a pressure wastewater main and ultimately to a wastewater treatment plant.

[0025] FIG. 3 illustrates a block diagram of a portion of a prior art grinder pump assembly employing a motor control assembly 300 for use in operating a grinder pump having a motor 390 with a run winding 392 and a start winding 394. Motor control assembly 300 includes an AC contactor 320, a bimetallic disc 350, a mechanical motor start switch 360, and a start capacitor 380. AC contactor 320 includes multiple contacts and a coil 322. Coil 322 is energized with AC current to control AC contactor 320 to control AC current to motor 390. A water ON/OFF switch 310 such as a low-level/on-off switch and/or a high-level on-off switch for a grinder pump is operably electrically connected to AC contactor 320 having multiple contacts one of which used and disposed in a normally open configuration and connected to bimetallic disc 350, which bimetallic disc 350 provides overcurrent protection. Mechanical motor start switch 360 is operably connected to run winding 392 of motor 390, and operably connected to start capacitor 380, which start capacitor 380 is operably connected to start winding 394 of motor 390. Mechanical motor start switch 360 includes a magnetic reed switch and snubberless TRIAC. When water switch 310 is activated such as when the water rises sufficiently in a sewage tank, AC contactor 320 is closed providing electric current to pass through bimetallic disc 350 and electric current is provided to run winding 392. The magnetic reed switch includes a coil of wire in which upon startup current flows therethrough to create a magnetic field to close a reed switch contact to activate a gate of the snubberless TRIAC, which snubberless TRIAC also allows current to be provided to the start winding of the motor. After the motor starts rotating and reaches a percentage of its rated full load speed (a short duration after starting such as milliseconds), current through the reed switch drops reducing the magnetic field to open the contact causing deactivation of the gate of the snubberless TRIAC to turn off current to the start winding of the motor.

[0026] FIG. 4 illustrates a block diagram of a portion of another prior art grinder pump assembly employing a motor control assembly 400 and an over/under wattage protection assembly 470 for use in operating a grinder pump having a motor 490 with a run winding 492 and a start winding 494. Motor control assembly 400 includes an AC contactor 420, a bimetallic disc 450, mechanical motor start switch 460, and a start capacitor 480. AC contactor 420 includes multiple contacts and a coil 422. Coil 422 is energized with AC current to control AC contactor 420 to control AC current to motor 490. A water ON/OFF switch 410 such as a low- level/on-off switch and/or a high-level on-off switch for a grinder pump is operably electrically connected to AC contactor 420 having multiple contacts controlled by an AC voltage one of which used and disposed in a normally open configuration and connected to bimetallic disc 450, which bimetallic disc 450 provides overcurrent protection. Mechanical motor start switch 460 is operably connected to run winding 492 of motor 490, and operably connected to capacitor 480, which start capacitor 480 is operably connected to start winding 494 of motor 490. Mechanical motor start switch 460 includes a magnetic reed switch and snubberless TRIAC. When water switch 410 is activated such as when the water rises sufficiently in a sewage tank, AC contactor 420 is closed providing electric current to pass through bimetallic disc 450 and electric current is provided to run winding 492. The magnetic reed switch includes a coil of wire in which upon startup current flows therethrough to create a magnetic field to close a reed switch contact to activate a gate of the snubberless TRIAC, which snubberless TRIAC allows current to also be provided to the start winding of the motor. After the motor starts rotating and reaches a percentage of its rated full load speed (a short duration after starting such as milliseconds), current through the reed switch drops reducing the magnetic field to open the contact causing deactivation of the gate of the snubberless TRIAC to turn off current to the start winding of the motor. Over/under wattage protection assembly 470, provided in a control panel disposed away from the sewage tank, includes an AC contactor 472 disposed in a closed configuration, a current sensor 474, and a timing circuit 476. Over/under wattage protection assembly 470 is provided between the electrical power supply and water ON/OFF switch 410. The over/under wattage protection assembly monitors higher than normal power (wattage) to the motor such as due to high pressure, AC controller is opened to disable (turn off) the motor, and determine how long that the motor should be off to cool down before the motor is able to be restarted. After three lockout attempts, manual activation of a circuit breaker controlling AC current to the grinder pump is required before operating the grinder pump again.

[0027] FIG. 5 illustrates a block diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure employing a motor control assembly 500 for use in operating a grinder pump having a dual voltage motor 590 such as a grinder pump motor having a run winding 592 and a start winding 594. In this illustrated embodiment, motor control assembly 500 includes a solid state motor start circuit 570. Motor control assembly 500 may be employed in the lower- pressure grinder pump system 100 (FIG. 1 ) in place of motor control assembly 200 (FIG. 1 ).

[0028] For example, motor control assembly 500 may include an AC contactor 520, a bimetallic disc 550, solid state motor start circuit 570, and a start capacitor 580. AC contactor 520 includes multiple contacts and a coil 522. Coil 522 is energized with AC current to control AC contactor 520 to control AC current to motor 590. A water ON/OFF switch 510 such as a low-level/on-off switch and/or a high-level on-off switch for a grinder pump is operably electrically connected to AC contactor 520 having multiple contacts one of which used and disposed in a normally open configuration and connected to bimetallic disc 550, which bimetallic disc 550 provides overcurrent protection. Solid state motor start circuit 570 may be operably connected to run winding 592 of motor 590, and operably connected to start capacitor 580, which start capacitor 580 is operably connected to start winding 594 of motor 590.

[0029] FIG. 6 illustrates a block diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure employing a motor control assembly 700 for use in operating a grinder pump having a dual voltage motor 790 such as a grinder pump motor having a run winding 792 and a start winding 794. In this illustrated embodiment, motor control assembly 700 includes a DC control switch assembly 740 and a solid state motor start circuit 770. Motor control assembly 700 may be employed in the lower-pressure grinder pump system 100 (FIG. 1 ) in place of motor control assembly 200 (FIG. 1 ).

[0030] For example, DC control switch assembly 740 may include a DC relay 742 having contacts disposed in a normally open configuration, and a DC coil driver circuit 744. A water ON/OFF switch 710 such as a low-level/on-off switch and/or a high-level on-off switch for a grinder pump may be operably connected to DC control switch assembly 740. Solid state motor start circuit 770 may be operably connected to run winding 792 of motor 790, and operably connected to start capacitor 780, which a start capacitor 780 is operably connected to start winding 794 of motor 790 as similarly described above in connection with solid state motor start circuit. When water switch 710 is activated such as when the water rises sufficiently in a sewage tank, DC coil driver circuit 744 is activated to close normally open DC relay 742 and allow AC current to flow to run winding 792 of motor 790. When the grinder pump motor reaches a percentage of its rated speed the current drops in the run winding (a short duration after starting such as milliseconds), AC current is disconnected from start capacitor 780 and start winding 794.

[0031] In some embodiments, motor control assembly 700 may also include an AC voltage monitoring circuit 741 operably connected to the AC mains of incoming power to measure incoming voltage levels to selectively control DC coil driver circuit 744. AC voltage monitoring circuit 741 is operable to monitor the AC voltage, and if within limits, DC coil driver circuit 744 allows the DC relay 742 to become energized thereby providing power to the motor, and if outside of limits, DC coil driver circuit 744 is inhibited from energizing the DC relay 742, thereby preventing AC power to the motor. [0032] DC coil driver circuit 740 may be operable in response to a coil driver inhibiting circuit 746 and on/off switch 710. Coil driver inhibiting circuit 746 may be operably connected to on/off switch 710 in order to inhibit DC coil driver circuit 740 by way of an inhibiting transistor. The inhibiting transistor accepts signals from and works in conjunction with AC voltage monitoring circuit 741 and an AC current sensing circuit, and may be incorporated in state motor start circuit 770, to inhibit DC coil driver 744 under non-ideal operating conditions for motor 790.

[0033] FIG. 7 illustrates a block diagram of a portion of a grinder pump assembly according to an embodiment of the present disclosure employing a motor control assembly 900 for use in operating a grinder pump having a motor 990 such as a dual voltage grinder pump motor having a run winding 992 and a start winding 994.

[0034] As described in greater detail below, motor control assembly 900 may generally include a DC control switch assembly 940, and a solid state motor start circuit 970. In some embodiments, motor control assembly 900 may further include an overcurrent protection circuit 2000 and/or a locked rotor protection circuit 3000.

[0035] With reference to FIG. 7, DC control switch assembly 940 may include an AC voltage monitoring circuit 941 , a DC relay 942, a DC coil driver 944, and a coil driver inhibiting circuit 946. A water ON/OFF switch 910 such as a low-level/on-off switch and/or a high-level on-off switch for a grinder pump may be operably electrically connected to DC control switch assembly 940. DC coil driver 944 may include a DIAC trigger and an SCR. When water switch 910 is activated such as when the water rises sufficiently in a sewage tank, DC coil driver circuit 944 controls operation of DC relay 942 to close a normally open contact to allow AC current to flow to run winding 992 of motor 990.

[0036] Upon start up, AC current to run winding 992 passes through a primary winding 932 of a transformer 930.

[0037] In motor control assembly 900, a precision resistor 933 may be placed across secondary winding 934. The secondary current creates an AC voltage across this resistor. Current sensing circuit 1000 may monitor voltage across this resistor with the voltage corresponding to the AC current is that is flowing through motor run winding 992. AC current sensing circuit 1000 may be operable with or as part of solid state motor start circuit 970, overcurrent protection circuit 2000, and/or locked rotor protection circuit 3000 as described below.

[0038] Solid state motor start circuit 970 includes a start current detector circuit 971 operably connected to AC current sensing circuit 1000 and to a zero crossing opto-TRIAC driver 972, which zero crossing opto-TRIAC driver 972 is operably connected to a solid state snubberless TRIAC start switch 973. Solid state snubberless TRIAC start switch 973 when triggered allows AC current to flow through a start capacitor 980 to start winding 994.

[0039] With reference still to FIG. 7, upon startup of the motor (DC relay 942 closes and AC current passes though primary winding 932 of transformer 930 and the motor being stalled and not rotating while drawing large current), solid state motor start circuit 970 senses this large draw in current upon start-up by way of AC current sensing circuit 1000, and AC current is provided to the start winding (as described above) via start capacitor 980 resulting in a rotating field in the motor allowing the motor to rotate, and within for example, about 100 milliseconds to about 150 milliseconds the motor begins to rotate and get up to speed resulting in a current drop, through run winding 992 and primary winding of transformer 930 and then AC current to the start winding is turned off based on the current drop. For example, the physical components of the circuity of the solid state motor start switch (e.g., some of which may include resistors) may be tailored to turn on at a desired sensed current and turn off at a desired sensed current as sensed by the AC current sensing circuit 1000. As also shown in FIG. 7, motor control assembly 900 may also include overcurrent protection circuit 2000 and/or a locked rotor protection circuit 3000 according to embodiments of the present disclosure.

[0040] Overcurrent protection circuit 2000 may include AC current sensing circuit 1000, an overcurrent delay timer circuit 1 100, delayed restart timer/unlock latch circuit 1300, and a protection shutdown/latch circuit 1400. Overcurrent protection circuit 2000 may be operable in the event that the motor starts running and the motor start winding turns off, but the motor draws a higher than standard operating current (for example due to high system head pressure, a partially blocked or restricted discharge line, low motor voltage) as indicated by overcurrent delay timer circuit 1 100 monitoring AC current sensing circuit 1000 but not high enough to cause the start switch to allow current to the start winding. In this case, the motor may get too hot and continued operation at the higher current draw increases the chances of motor failure. Overcurrent delay timer circuit 1100 is operably connected to protection shutdown/latch circuit 1400, which protection shutdown/latch circuit 1400 may be operable to prevent the motor from operating for a short period of time (e.g., for about 5 seconds) at the higher current draw by activating the motor protection and shutdown/latch 1400 and simultaneously beginning a delayed restart timer/unlock latch circuit 1300, to inhibit motor operation by a combination of coil driver inhibit circuit 946, DC coil driver 944, and DC relay 942, and wait a period of time (e.g., minutes) before releasing protection shutdown/latch circuit 1400, restarting the motor by removing the motor inhibit by a combination of the coil driver inhibiting circuit 946, DC coil driver 944, and DC relay 942, to avoid the likelihood of damage or failure of the motor windings or motor start capacitor.

[0041] Locked rotor protection circuit 3000 may include AC current sensing circuit 1000, start current detector circuit 971 , locked rotor delay timer circuit 1200, delayed restart timer/unlock latch circuit 1300, and protection shutdown/latch circuit 1400. Locked rotor protection circuit 3000 may be operable in the event that the motor draws a higher than standard operating current, (for example due to an obstruction that prevents the rotor from turning (locked rotor), a completely blocked discharge line or low motor voltage), for a long enough duration as indicated by locked rotor delay timer circuit 1200 monitoring AC current sensing circuit 1000, where the current remains high enough to keep the solid state start switch and the start winding engaged. If left in this state, the motor and/or motor start capacitor will likely overheat and fail. Locked rotor delay timer circuit 1200 is operably connected to protection shutdown/latch circuit 1400, which protection

shutdown/latch circuit 1400 may be operable to prevent the motor from operating for a short period of time (e.g., for about 500 milliseconds to about 4 seconds) at the higher current draw by activating the motor protection shutdown/latch circuit 1400, and simultaneously begin a delayed restart timer/unlock latch circuit 1300, to inhibit motor operation by a combination of the coil driver inhibiting circuit 946, DC coil driver 944, and DC relay 942, and wait a period of time (e.g., minutes) before releasing the protection shutdown/latch circuit 1400, restarting the motor by removing the motor inhibit by a combination of the coil driver inhibit circuit 946, DC coil driver 944, and DC relay 942, to avoid the likelihood of damage or failure of the motor windings or motor start capacitor.

[0042] Both the overcurrent protection circuit 2000 and the locked rotor protection circuit 3000 may be tailored to function at various current limits and as well as overcurrent delay timer circuit 1 100 and locked rotor delay timer circuit 1200 may be tailored to function at various elapsed times of elevated current draw (different than about 2 seconds and different from about 5 seconds) by specific physical passive components selection within the respective circuits.

[0043] In other situations in operating a grinder pump system, if for example a discharge valve of sewage tank is closed or blocked such as frozen or partially frozen, the pump can draw abnormally high pressure. In some situations, a blockage may prevent the grinder pump from starting and the start capacitor may fail due to numerous attempts to restart the grinder pump. In some embodiments according to the present disclosure, the overcurrent circuit, the locked rotor protection circuit, or a separate blocked protection circuit may be employed to prevent damage to the start capacitor and/or to the motor. For example, the overcurrent circuit, the locked rotor protection circuit, or a separate blocked protection circuit may be designed to relate a pressure to a current that can be used to trip (turn off the motor via the DC control relay) at a safe threshold.

[0044] DC control switch assembly 940 may include an AC voltage monitoring circuit 941 according to an embodiment of the present disclosure, wherein, upon closure of the external water level ON/OFF switch 910, motor starting will be initially inhibited by the AC voltage monitor circuit 941 latching on the coil driver inhibiting circuit 946, until the voltage rises above a minimum threshold to guarantee safe motor operation. The AC voltage monitor circuit 941 then latches off the coil driver inhibiting circuit 946 activating DC coil driver 944 and DC relay 942 allowing the motor to start. If after the motor starts running and the motor start switch is off, if the voltage level then falls below a minimum threshold to guarantee safe motor operation, the AC voltage monitor circuit 941 will latch on the coil driver inhibiting circuit 946 and through DC coil driver 944 and DC relay 942, immediately stop the motor from running. The voltage threshold allows for a dip in AC voltage that occurs under a normal motor start, but which recovers quickly, as to not activate the AC voltage monitoring circuit 941. The motor could shut off due to the low voltage protection as a result of the dip in AC voltage that accompanies a normal motor start, and then turn back on after recovery from said dip, resulting in a rapid cycling of the motor and start circuit, which for an AC motor is detrimental to the motor and the motor start capacitor. Low voltage operation may result in the motor getting too hot and if the motor continues to operate at the lower voltage the likelihood is possible for damage or failure of the motor windings or motor start capacitor.

[0045] DC control switch assembly 940 may include an AC voltage monitoring circuit 941 according to an embodiment of the present disclosure, whereby operation of the DC coil driver 944 and DC relay 942 are dependent upon the incoming AC voltage sensed by the AC voltage monitoring circuit 941 to guarantee that the DC relay 942 does not become opened due to a voltage too low to guarantee the coil of the DC relay will remain energized to cause the contacts to remain closed. Without AC voltage monitoring circuit 941 , an undesired state of the relay could exist whereby the relay contacts open, but could never become closed again unless AC power to the circuit was removed completely, for example by cycling the breakers that supply AC power to the circuit. The interaction between the AC voltage monitoring circuit 941 and the DC coil inhibiting circuit 946 guarantees this scenario never occurs.

[0046] This unit provides a way in which the circuit verifies proper input voltage through on/off switch. Incoming voltage from the on/off switch for normal operation acts upon a Schmitt trigger. This initial voltage is high enough to keep the trigger in an "off" state. Because of the inherent design of the coil driver, this voltage is high enough to properly operate the motor. If during motor operation the voltage were to drop below acceptable levels, it would engage the Schmitt trigger and set it to an "on" condition. That condition engages the inhibiting transistor and shorts the coil driver. This effectively protects many of the components from the negative effects of low voltage operation. [0047] The present disclosure may address false triggers from charge buildup due to capacitive coupling in the tray cable. For example, due to the design of the overall system, it is possible for charge to build up in the bulk storage capacitor due to capacitive coupling within the tray cable that connects this motor to incoming power. If that charge fully energizes a storage capacitor in the circuit, it is possible for the capacitor to discharge and provide a "false trigger" to the relay. This operates the motor for a very short time, and can be damaging. In order to prevent this, a load resistor 947 is included to the standard coil driver.

[0048] From the present disclosure, it will be appreciated that current from secondary winding 934 of transformer 930 allows performing sensing the need to start the pump, sensing an overcurrent event or locked rotor or blocked discharge event, and removing power from the pump altogether. These functions may be mutually exclusive events.

[0049] A waiting factor or a duration of time can be provided prior to attempting to restart the motor allowing the motor to cool down, for example for a time deemed necessary by the requirements of the system. The present disclosure overcomes the time sensitive problems of the prior art due to the limitations of a bimetallic disc to avoid the likelihood of damage to the motor, pump, or start capacitor. For example, the capacitor has a duty cycle rating, whereby if energized too rapidly in succession such as by continuously re-engaging of the start switch, start winding, and start capacitor, the capacitor will heat up. The limitations of the bimetallic disc are such that a repeatable, and or adequate time period may not be provided to prevent this scenario.

[0050] By employing passive and solid state components such as resistors and capacitors for the timers, TRIACs, among other solid state components, the operating parameters may have close tolerances and do not require calibration for operation. In other embodiments, the various circuitry of the motor controller may be incorporated with one or more microcontrollers or processors with or without programming and/or calibration.

[0051] FIG. 8 is a schematic diagram of a motor control assembly 4000 according to an embodiment of the present disclosure having a solid state motor start circuit, an AC voltage monitor circuit, a DC control switch, an overcurrent protection circuit, and a locked rotor protection circuit as described above. Motor control assembly 4000 may be employed in the lower-pressure grinder pump system 100 (FIG. 1 ) in place of motor control assembly 200 (FIG. 1 ).

[0052] With reference to FIGS. 7 and 8, the various components may be operable to provide the following: a) A capacitor input power supply charges a bulk storage capacitor. The DC current provided by this circuit is dependent on the capacitance of the input AC capacitor, the AC voltage and the line frequency, and on the charge in the bulk storage capacitor. b) A load resistor disposed across the AC input to dissipate AC leakage caused by the tray cable. Without this load removing leakage, the capacitor input supply may slowly charge the bulk storage capacitor, which may then cause the relay to activate occasionally and unpredictably. c) A DIAC monitors the bulk storage capacitor and when the voltage is high enough, it provides a gate trigger to a Silicone Controlled

Rectifier (SCR). d) A SCR latches on when triggered, completing the circuit for the coil of a relay with the energy stored in the bulk storage capacitor. e) A relay with contacts to provide AC power to the motor. f) An AC voltage monitor circuit that inhibits the bulk storage capacitor from charging unless the AC voltage is above a threshold and that also causes the bulk storage capacitor to be discharged if the AC voltage falls below a threshold for too long a time. This circuit may have a short time delay to allow for a momentary dip in the AC voltage when the motor is starting. g) A shorting transistor to discharge the bulk storage capacitor. The shorting transistor reacts to two different conditions. It may be controlled by the AC voltage monitor circuit, and also by an overcurrent sensing circuit (over-pressure and locked rotor). The overcurrent sensing circuit may include a timer to control the restart time delay.

[0053] Characteristics of a DC coil relay and of a SCR may include the following benefits. For example, a DC coil relay that requires at least 80% of rated coil voltage to turn on, but once turned on, requires only 30% of rated coil voltage to remain on. Below about 25% of rated coil voltage, the

magnetic field is not strong enough to overcome the contact spring tension, and the contacts can no longer mechanically remain closed. Due to the wide range of magnetic field required to keep the contacts closed, and with DC power to supply a continuous magnetic field, the DC coil relay cannot chatter like an AC coil relay. An advantage with a DC coil relay is that the voltage can be lowered after the relay has turned on. This allows the relay to be efficient and the coil to run much cooler, and increases the contact current rating and the ambient temperature rating. Using a capacitor input DC power supply is ideally suited to operate a DC coil relay with an AC power supply. The DC power supply is simple, compact, efficient, and cost effective. The supply is sized to provide less than the rated coil current to take advantage of the DC coil characteristics.

[0054] Due to its construction, an AC coil relay requires a higher current to close its contacts, than to hold them closed, by a factor of about 10. This is due to inductance, such that when the AC relay is off, there is a physical gap in the armature, which results in low inductance, and causes a much higher AC current to flow. After the contacts close, the air gap is significantly reduced and the inductance increases, thereby lowering the AC current. If the contacts cannot completely close, the coil will catastrophically overheat due to the higher current lasting longer than the coil was designed to handle. A DC relay eliminates this problem.

[0055] A SCR is a semiconductor device that is held, or latched, in its on or conducting state, once current flows. In order to return to its off state the current through the SCR must be removed. SCR's are often used in AC circuits because the sinusoidal AC current waveform always passes through zero, removing current through the SCR, turning it off automatically after each half cycle of the waveform.

[0056] SCR's have a minimum hold current rating. The SCR, use in the present disclosure has a hold current of about 5ma. The dropout current of the 24VDC relay is about 8ma or 9ma, and so the 24VDC relay may turn off before the SCR. This can happen if the AC power drops too low to maintain the contact closure of the relay, but not low enough to shut off the SCR, and then recovers. If the SCR did not turn off, the DC voltage on the bulk storage capacitor is unable to get high enough to cause the DC relay to close due to the SCR still completing the circuit to the coil. The result is that the pump will be unable to run again unless the AC power is turned off and then back on.

The makeup of the AC Voltage monitoring circuit is such that the SCR will always turn off before the relay, so it can re-trigger when the AC voltage to the circuit is restored.

[0057] A reason for the AC voltage monitor range is that the SCR needs to be forced to turn off, thereby shorting out the DC supply and turning it off, before the AC voltage drops below about 125VAC. In addition, it is desirable to allow the DC supply to come back on when the AC voltage gets up to about 180VAC. Because the AC voltage monitoring circuit uses the hysteresis points of a Schmitt inverter as a comparator, the accuracy of the low and the high AC voltage points is only about 15%. As a result, the minimum low point needs to be set above the voltage where the relay drops out, but also the maximum high point must not be set above the minimum normal AC voltage.

[0058] FIG. 9 illustrates a motor control assembly 5000 according to an embodiment of the present disclosure. Motor control assembly 5000 include a motor control assembly disposed on a single circuit broad 5010 and covered with a board protection 5020, a start capacitor 5040, and a bracket 5060 for attaching motor control assembly 5000 to a motor such as a grinder pump motor. Motor control assembly 5000 may include the features of the present disclosure described herein.

[0059] FIG. 10 illustrates a method 6000 for controlling a motor having a run winding and a start winding according to an embodiment of the present disclosure. Method 6000 includes, for example, at 6100 providing DC power to control AC power to the run winding of the motor from an AC power supply, at 6200 sensing the current of the AC power to the motor, at 6300 connecting AC power through a start capacitor to the start winding of the motor based on the sensed current of the AC power to the motor, at 6400 sensing AC voltage of the AC power supply, and at 6500 inhibiting the DC power to shut down the AC power to the run winding of the motor based on the sensed AC voltage of the AC power supply.

[0060] Benefits of the present disclosure may include the following:

Elimination of the current bimetallic disc overcurrent protection device. While a bimetallic disc opens in response to an elevated temperature typically coinciding with a high current draw of the motor, thereby removing current from the motor windings, it does so within an unreliable and unrepeatable time to both trip, and recover from said event. If recovery from such an event occurs too soon the motor windings and start capacitor are not afforded adequate time to cool, and if allowed to persist, can overheat and fail.

Elimination of the mechanical reed switch that is inherent to the present motor start switch. The electrical characteristic of this switch are highly dependent on its physical makeup, and as a result, delicate assembly and subsequent calibration are required to ensure proper operation. Furthermore, the presence of electrical noise and or harmonics, as well as any distortions of phase, e.g. dirty power, introduced on the incoming sinusoidal AC waveform can have an adverse effect on this type of start switch, resulting in a scenario where the switch is unable to perform and allow the motor to start reliably.

Elimination of the AC contactor. AC contactors are inherently prone to rapid cycling on and off, e.g. chatter, in response to distorted or low incoming AC voltage. Furthermore, short duration dips in the incoming AC voltage, for example such as may be seen when there is a significantly long cable run between the power source and the motor, or when using a portable generator to provide power to start the motor, can cause an AC contactor to become de-energized briefly, only to be re-energized once said dip is recovered. Use of a DC coil and associated DC coil driver circuit ensures that adequate power to the coil is maintained due to the use of a bulk storage capacitor that provides energy throughout such a dip in incoming voltage.

Provides overcurrent/over pressure protection.

Provides locked rotor protection.

Provides a longer rest period before re-starting.

Provides low voltage protection - the circuit waits for the AC voltage to be high enough before trying to run the motor. This also allows for a substantial voltage dip - without dropping out, while the motor is starting, which can happen with a long cable run, or with some portable AC generators.

Reduces possibility of splitting of the stator cup due to over pressure and high temperature. Reduces possibility of over pressure causing failure of the discharge piping.

The new board provides over-pressure protection electronically, with no additional manufacturing expense or extra parts to replace.

The printed circuit board may be populated differently to operate at several specific start currents and line voltages, to use in any of our various motors designed for different AC voltages, RPM, and line frequency.

Allow use with motor windings from different motor suppliers. Easier attachment of a motor control assembly and bracket with less wiring required.

Easier servicing in the field with less parts and less wiring.

[0061] The solid state motor start switch of the present disclosure overcomes problems with prior art mechanical start switches such as described above in connection with FIGS. 3 and 4. For example, the reed switch requires careful manufacture in order to properly tune or configure the reed switch for proper function of the mechanical start switch. The motor control assembly of the present disclosure may be easier to install, less likely to be miss wired, less prone to loosening wires, easier to trouble shoot, easier to replace.

[0062] An advantage of the present motor control assembly employing a DC relay and DC relay driver is a reduction in size and cost compared to a mechanical start switch employing a contactor. Employing a DC relay operated by DC coil driver as in the present disclosure requires that the voltage needs to rise above a certain level to turn on the relay and the voltage has to fall below a lower level in order to turn off. By providing a region between turning on and turning off, e.g. hysteresis, the likelihood of dropout due to power dip while starting is eliminated.

[0063] Further advantages of the motor control assembly of the present disclosure is that the components may be easily assembled and connected to a printed circuit board, be compact, provide reliable long life, decreased cost, not require calibration, and does not have to be programmed compared to mechanical start switch assembly having a magnetic reed that requires time consuming assembly and calibration.

[0064] The motor control assembly of the present disclosure may be operable with use in capacitor start motors from fractional horsepower to 2 horsepower range or other range. For example, the relay and DC coil driver circuit may be used in other systems.

[0065] In addition, motor control assembly of the present disclosure may allow for different motor winding configurations and also motor suppliers. Motor control assembly of the present disclosure may also be employed to run lower or higher horse power motors. The motor control assembly of the present disclosure may be wireless or explosion proof.

[0066] Also the motor control assembly of the present disclosure may be a replacement motor control assembly that may be readily used on existing motors to replace existing motor control assemblies having a mechanical motor start switch.

[0067] The motor control assembly of the present disclosure provides a relatively simple electronic current measuring circuit. This circuit provides the drive to a triac using a zero-crossing triac driver that is not dependent on the phase of the incoming power. The circuit also provides current measurement to provide protection for overpressure and locked rotor, with a slow and fast timing response similar to the existing bimetallic disc time response but without the use of a bimetallic disc and the inherent problems. The new circuit includes a timer such as a precision timer, to prevent re-starting rapidly and to allow time to cool down, overcoming the problem of a thermal switch rapid cycling. The new circuit also may employ a common board mount DC relay, which cannot chatter and at lower cost compared to an AC contactor. Two cap-input power supplies that are efficient, compact, and simple power the board. An additional result of the present disclosure is that the power supply does not emit any radio frequency interference, for example, such would be present with a switching power supply.

[0068] The motor control assembly of the present disclosure does not need to be hand calibrated; it is inherently more accurate than the mechanical switch by using a standard 1 % resistors and reference for current measurement. By selecting different values of certain components on the printed circuit board, the new design is versatile for any voltage, frequency, or motor winding. The motor control assembly of the present disclosure may replace control units and fit easily in existing motors and pump. The new assembly may also be built and tested by any manufacturer of printed circuit boards. The improved design may result in less pump repairs and with fewer parts in the pump, and quicker and simpler wiring.

[0069] It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments and/or aspects thereof may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments without departing from their scope.

[0070] While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments, they are by no means limiting and are merely exemplary. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0071] In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §1 12, sixth paragraph, unless and until such claim limitations expressly use the phrase "means for" followed by a statement of function void of further structure.

[0072] It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0073] While the disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described embodiments. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

[0074] This written description uses examples in the present disclosure, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.