CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application Serial No. 62/893,859 filed on August 30, 2019, the contents of which are incorporated herein in its entirety.

BACKGROUND

[0002] Cable pulling is a commonly used technique in high-force rope pulling operations, such as wire conduit pulling, ship or oilfield use, whereby a pulling line is attached to an electrical cable or wire that is to be pulled through conduit or along a cable tray by a cable puller. The conduit or cable tray may be any length and may contain any number of bends, turns, or other layout characteristics.

[0003] Cable pullers are known in the art. The cable puller may, for example, be mounted to the floor or may be mounted on a wheeled carriage. The pulling line is wound by an operator around a capstan rotatably mounted on a cable puller housing of the cable puller and tails off the capstan. The capstan is powered by a cable puller motor mounted on the cable puller housing.

[0004] One end of the pulling line is connected to the object being pulled, while the other end of the pulling line is pulled by the cable puller. The pulling line is wound by an operator around a capstan on the cable puller and the operator then pulls on the free, loose end of the pulling line. The capstan is powered by the motor. As the motor turns the capstan, the friction of the pulling line on the capstan offloads most of the pulling force to the motor, requiring the operator to manually “tail” the free, loose end of the pulling line by applying a tailing force to the free, loose end of the pulling line to maintain friction of the pulling line on the capstan.

[0005] Use of the cable puller to pull the electrical cable or wire through the conduit or along the cable tray allows the operator to exert only a small force on the pulling line that tails off of the capstan. This relatively small force is translated into a large force of several thousand pounds which is exerted on the incoming pulling line and which provides enough force on the pulling line and the electrical cable or wire to pull them through the conduit or along the cable tray.

[0006] Most known cable puller motors are basic AC motors, which are coupled to the 120V AC mains power supply. The only power control is typically an on-off switch. When in use during the cable pulling process, a load on the capstan may become excessive, which may induce a motor stall condition. During this motor stall condition, the motor may draw excessive current sufficient to trip the mains circuit breaker. When this occurs, time is lost and work expense increases.

|0007] Generally, such AC motors may be optimized by design for a particular fixed power factor because the rated speed (RPM) of the motor may be fixed and is not controllable. Such design factors may include the number and dimension of windings, the core and rotor configuration, material composition, and the like. However, because the speed of such motors cannot be controlled, adverse conditions, such as stall conditions, cannot be easily handled.

[0008j Other cable pullers may use a variable speed DC motor. However, such known DC motors have a poor power factor. This poor power factor prevents the device from drawing the maximum power from the source or mains without drawing high RMS current, thereby limiting the useful power delivered to the motor load. High RMS current tends to trip the source circuit protection, such as the circuit breaker or fuse. The high RMS current for the given input power is due to the current transfer having high peaks and narrow conduction time.

|0009] A need exists for a cable puller motor and power supply that provides a high power factor correction (PFC) to maximize the amount of power drawn from the source with minimum RMS current, thereby maximizing the power available to the load motor.

SUMMARY

100.1.0j According to one specific embodiment, a power supply provides power for a cable puller motor, where the motor is operatively coupled to a cable puller assembly and is configured to drive a capstan that provides a pulling force on a pulling line wrapped around the capstan. The power supply is operatively coupled to an AC mains source of power. The power supply includes a bridge rectifier configured to rectify AC power provided by the AC mains and a chopper power controller configured to generate a pulse- width modulated (PWM) DC output power signal, based on received voltage and current signals. Such signals may include a DC bus voltage signal, a reference voltage signal, a mains current signal, and a motor current signal. Also includes is an output power circuit having a plurality of semiconductor switches responsive to the PWM DC output power signal so as to turn on and off the semiconductor switches in a controlled sequence so as to control power provided to the motor. A power factor pre-regulator is operatively coupled to a DC bus, where the power factor pre-regulator and the chopper power controller cooperate to maximize a power transfer from the AC mains to the motor.

[0011 j In another embodiment a power supply provides power for a cable puller motor, where the motor is operatively coupled to a cable puller assembly and configured to drive a capstan that provides a pulling force on a pulling line wrapped around the capstan. The power supply is operatively coupled to an AC mains source of power and includes a rectifier configured to rectify AC power provided by the AC mains, a chopper power controller configured to generate a pulse-width modulated (PWM) DC output power signal, based on received voltage and current signals, a power factor pre-regulator operatively coupled to a DC bus, where the power factor pre-regulator is configured to maximize a power transfer from the AC mains to the motor. The power factor pre regulator includes a power factor controller configure to generate a PWM switching output signal that modulates current flow in an output capacitor of the DC bus.

[0012] In a further embodiment a power supply provides power for a cable puller motor, where the motor is operatively coupled to a cable puller assembly and configured to drive a capstan that provides a pulling force on a pulling line wrapped around the capstan. The power supply is operatively coupled to an AC mains source of power and includes a bridge rectifier configured to rectify AC power provided by the AC mains, a chopper power controller configured to generate a pulse-width modulated (PWM) DC output power signal based on a plurality of received voltage and current signals. The chopper power controller is configured to control a plurality of semiconductor switches responsive to the PWM DC output power signal so as to turn on and off the semiconductor switches in a controlled sequence to provide a chopped DC power signal to the cable puller motor.

BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is graph showing three AC waveforms.

[0014] FIG. 2 is a high-level electrical block diagram of a known power circuit for use in a cable puller machine.

[0015} FIG. 3 is a high-level electrical block diagram of one embodiment of a power supply arrangement for use in a cable puller machine.

[0016] FIG. 4 is a flowchart showing operation of a power controller in the power supply arrangement of FIG. 3, according to one embodiment.

[0017] FIG. 5 is a simplified schematic diagram of a rectifier circuit and DC bus of FIG. 3, according to one embodiment.

[0018] FIG. 6 is a simplified schematic pictorial diagram of the output power circuit of FIG. 3, according to one embodiment, showing a plurality of motor control switches. [0019] FIG. 7 is a schematic diagram of power transistors used in the output power circuit shown in FIG. 6, according to one embodiment.

[0020] FIG. 8 is a simplified schematic diagram of an alternate embodiment of the output power circuit of FIG. 3, according to one embodiment.

[0021] FIG. 9 is a simplified schematic diagram of the power factor correction pre regulator of FIG. 3, according to one embodiment.

DETAILED DESCRIPTION

[0022] While the disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that as illustrated and described herein. Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity. It will be further appreciated that in some embodiments, one or more elements illustrated by way of example in a drawing(s) may be eliminated and/or substituted with alternative elements within the scope of the disclosure.

[0023] FIG. 1 is a graph showing three AC waveforms. A first waveform 12 shows the input voltage provided by the mains 120-volt AC to a power supply of a cable puller machine (cable puller not shown). The mains power is typically coupled to a 20-amp circuit breaker but may vary depending on the site.

[0024] The second waveform 14 shows a current spike drawn from the mains power, which may be caused by uncompensated rectification of the power supply to the cable puller machine. Such a current spikes may cause the mains circuit breaker to trip. This current spike waveform 14 represents a high or excessive RMS current.

[0025] The third waveform 16 represents the current drawn from the mains by the motor power supply having a power factor control (PFC) circuit or PFC pre-regulator, in accordance with one embodiment of the present invention.

[0026] FIG. 2 is a high-level block diagram of a known motor power supply for a cable puller machine, which may control a DC motor, and which motor power supply may cause the current spikes show by waveform 14 of FIG. 1.

[0027] FIG. 3 is a high-level electrical block diagram of a cable puller power supply 300 according to one embodiment of the present invention. An AC electrical source 310, such as the mains 120-volt AC power source, provides power for the power supply 300. [0028] A rectifier circuit, such as a full-wave bridge rectifier circuit 320, may be operatively coupled to the mains power 310. The rectifier circuit 320 provides a rectified AC signal to a power factor correction (PFC) circuit or pre-regulator circuit 330. The output of the pre-regulator circuit 330 is provided to a DC bus circuit 340, which may include a plurality of fairly large capacitors configured “smooth” out the ripple in the rectified signal so as to approximate a DC voltage.

[0029] A chopper power controller 350 may receive the following signal inputs: A) a mains current signal 351, which may be measured at a node between the inductor L and the rectifier as seen in FIG. 9, B) a DC bus voltage output signal 354 from the DC bus 340, C) a first voltage reference signal 355 Vrefi, which may be any stable precision regulated reference voltage, and D) a motor output current signal 374 indicative of the motor current.

[0030] Based on the above-described four inputs, the chopper power controller 350, in turn, generates a pulse-width modulated (PWM) DC power signal 356 to an output power circuit 360 in the form of a variable duty-cycle rectangular waveform. This may also be referred to as a chopped DC power signal. The ratio of the on to off portions of the rectangular power waveform determine the power delivered to the motor 370 per unit time.

[0031] The output power circuit 360, in turn provides a switch arrangement that provides switching power in accordance with the PWM DC power signal 356 provided by the power controller 350, and where the output of the solid-state switches of the output power circuit 360 drives a DC motor or load 370. Examples of the output power circuit 360 may be shown in FIGS. 6-8. The output power circuit 360 also provides a feedback motor current signal 374 to the chopper power controller 350 representative of the current drawn by the motor 370. Any suitable current monitoring method may be used, including a shunt resistor, Hall devices, and the like.

[0032] The power supply 300 having such pre-regulator circuit 330 is able to maximize the amount of power drawn from the AC source or mains power 310 while drawing a minimum RMS current from the mains, thereby maximizing the effective power available to the motor 370. This reduces or eliminates the chance of tripping the mains circuit breaker during the pulling operation. The use of a pre-regulator circuit 330 also allows a wide range of source voltages and output voltages for use with various motors.

[0033} The chopper power controller 350 in conjunction with the pre-regulator circuit 330 allows a maximum speed of the motor 370 over a wide range of output loads. This increases time efficiency of the cable pulling work by maintaining a maximum motor speed (voltage, PWM duty cycle) until an input power level meets or exceeds a predetermined limit, such as when the motor is approaching a stall condition.

[0034] When a maximum power limit is met, meaning the maximum power is being drawn from the mains power 310, the chopper power controller 350 reduces the PWM DC power signal 356 ratiometrically (by modulation of the duty cycle) as motor current increases so as to maintain the mains power 310 maximum power draw without overload. The pre-regulator circuit 330 thus allows a maximum power transfer from the mains power 310 while using the lowest RMS current possible. |0035| The above power regulation process is further described in the flowchart of FIG. 4, which shows various steps that the power controller 350 may take. The chopper power controller 350 senses or measures the motor load via the motor output current signal 374, and also measures the voltage supplied to the motor via the DC bus voltage output signal 354, as shown in step 410. The power consumption is then calculated per step 414 using the motor output current signal 374, the DC bus voltage output signal 354, and the PWM DC power signal 356 is generated accordingly.

[0036] If the calculated power consumption is greater than a maximum or predetermined amount (step 416) as shown by the “YES” arrow 418, the motor speed is reduced by appropriate further modulation of the PWM DC power signal 356, as shown in step 420.

[0037] If the calculated power consumption comparison of step 416 is not at the maximum level, as shown by the “NO” arrow 426, a step 428 determines if the motor speed or motor voltage is at a maximum level, and if it is, as shown by the “YES” arrow 430, control branches to step 420 so that the motor speed is reduced by appropriate further modulation of the PWM DC power signal 356.

[0038] If the motor speed or motor voltage is not at a maximum level, as shown by a

“NO” arrow 434, a step 440 increases the motor speed or motor voltage by appropriate further modulation of the PWM DC power signal 356. The above steps repeat, as shown by the branch back to step 410 so as to provide continuous real-time control of the motor 370.

[0039] FIG. 5 is a simplified schematic diagram of the rectifier circuit 320 of FIG. 3. Other rectifier configurations are possible. For purposes of illustration, a full-wave bridge rectifier circuit is shown. Further, for purposes of clarity, only one DC bus capacitor of the DC bus 340 is shown, which may be an electrolytic capacitor or bank of capacitors.

[0040] FIG. 6 is a simplified schematic diagram of the output power circuit 360, which illustrates how power is turned on and turned off to the motor 370 under control of the PWM DC power signal 356 provided by the chopper power controller 350. In the illustrated simplified schematic view, the PWM DC power signal 356 controls each of the solid-state switches (SI, S2, S3, S4) so as to energize and deenergize the motor during the corresponding ON time. The amount of time that a particular pair of switches is closed or ON determines the average power provided to the motor 370, and hence motor speed.

[0041] The switches may be transistors or any semiconductor switch, such as power transistors in the form of FETs (field effect transistors), IGBTs (insulated-gate bipolar transistors), and the like. As shown, the output power circuit 360 can control the motor 370 in a forward and in a reverse direction. To operate the motor 370 in a first direction, switches SI and S4 are closed and power is thus applied, while switches S3 and S3 remain open. To operate the motor 370 in the opposite direction, switches S2 and S3 are closed and power is thus applied, while switches SI and S4 remain open. Half of the switches may be omitted if the motor 370 is to be operated only in one direction.

[0042} FIG. 7 is a schematic diagram of power transistors used to implement the switches shown in FIG. 6. As shown, each switch may be implemented using power transistors. For example, the power transistor representing switch SI may be connected in a high-side arrangement where, for example, the source is connected to V+ and the drain is connected to one side of the motor 370, while the other side of the motor is connected to ground. Alternatively, the power transistor representing switch SI may be connected in a low-side arrangement where, for example, one side of the motor is connected to V+ and the other side of the motor is connected to the source, while the drain is connected to ground.

[0043} FIG. 8 is a simplified schematic diagram of an alternate embodiment of the output power circuit 360. This circuit includes six transistor switches used to control a three-phase AC induction motor 802 or alternatively, a brushless DC motor, depending on the application and rated power requirements.

[0044j FIG. 9 is a schematic diagram of the pre-regulator circuit 330 of FIG. 3, according to one embodiment. FIG. 9 illustrates the AC source or mains power 310, the rectifier circuit 320, the load or motor 370, the DC bus or smoothing capacitors 340, and a PFC controller 900. The pre-regulator circuit 330, which is shown as a box in FIG. 3, may be formed in part by inductor L, diode D _PfC , and power factor correction transistor or switch 902 having a bypass diode DB as shown in FIG. 9.

[0045] As described above, the PFC controller 900 of FIG. 9 may operate in boost mode and provides the PWM switching output signal 956 based on a plurality of inputs. The PFC controller 900 of FIG. 9 is not to be confused with the chopper power controller 350 of FIG. 3, although some input signals are common to both components. Inputs to the PFC controller 900 may include: a. Vdc (354 DC bus voltage output signal, also shown in FIG. 3) b. Vref2 (960 stable regulated second reference voltage) c. Vac (952 measured at node between rectifier and inductor) d. I _(L) (972, current through inductor L)

[0046] Not that the duty cycle of the PWM DC power signal 356 provided by the power controller 350 in FIG. 3 is maintained to be ratiometric to the input voltage waveform, and thus provides a good power factor due to the ratiometric characteristic. The duty cycle is then scaled relative to the DC bus voltage to provide regulation.

[0047] Many modifications and other embodiments of the disclosure set forth herein will come to mind to one skilled in the art to which these disclosed embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed herein and that modifications and other embodiments are intended to be included within the scope of the disclosure. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated within the scope of the disclosure. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0048] While particular embodiments are illustrated in and described with respect to the drawings, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the appended claims. It will therefore be appreciated that the scope of the disclosure and the appended claims is not limited to the specific embodiments illustrated in and discussed with respect to the drawings and that modifications and other embodiments are intended to be included within the scope of the disclosure and appended drawings. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure and the appended claims.