FIELD OF INVENTION

[0001] The present subject matter is related to, in general, motor systems and, in particular, control of motor systems. BACKGROUND

[0002] A capacitor start and capacitor run (CSCR) motor may be used to drive a high-power pump. The pump is used to pump liquids, such as water, from one place to another, such as from a well to an overhead tank. The CSCR motor includes a start capacitor to start the motor and a run capacitor to run the motor. The start capacitor is disconnected once the motor attains a particular rotational speed, such as 75 % - 80 % of the maximum rotational speed.

BRIEF DESCRIPTION OF DRAWINGS

[0003] The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0004] Fig. 1 illustrates a motor system, in accordance with an implementation of the present subject matter;

[0005] Fig. 2 illustrates a method for controlling a motor, in accordance with an implementation of the present subject matter;

[0006] Fig. 3 illustrates a method for controlling a motor, in accordance with an implementation of the present subject matter; and

DETAILED DESCRIPTION

[0007] A capacitor start capacitor run motor (CSCR) may be used to drive a high-power pump. The CSCR motor includes a stator, a rotor, and a run capacitor. The stator includes a start winding and a run winding. The run capacitor is connected to the start winding and provides a phase difference of 90° between the start winding and the run winding. The motor also includes a start capacitor connected to the start winding to provide a phase difference of more than 90°, so that sufficient starting torque is obtained to start the motor. When the motor reaches a particular RPM, such as 75 % to 80 % of the maximum RPM of the motor, the start capacitor is disconnected from the circuit, as, at such a speed, the torque to run the motor can be supplied by the usage of the run capacitor alone.

[0008] In some scenarios, such as failure of motor bearing, deposition of debris on the pump, and the unavailability of adequate amount of liquid pumped by the pump (i.e., dry run condition), the motor experiences extreme load conditions, such as an overload condition or an underload condition. The extreme load conditions cause overheating of the motor and may eventually lead to the failure of the motor. To prevent the motor and the pump from damages caused due to the extreme load conditions, the extreme load conditions are to be detected and the current supply to the motor has to be cut off upon the detection.

[0009] In this regard, in some cases, to detect the overload condition and to subsequently stop the current supply, a thermal overload protector is used. The thermal overload protector has a thermal sensor to detect the temperature of the motor. When the current supplied to the motor increases, the temperature of the motor increases. When the temperature increases beyond an allowable value, the thermal overload protector opens to stop the current supply to the motor. However, the increase in temperature of the motor due to the increase in current may happen gradually. Therefore, the thermal overload protector takes time to detect the overloading condition, and thereby the protection of the motor may be hampered.

[0010] Further, as mentioned earlier, in the CSCR motor, the start capacitor is disconnected from the start winding when the motor reaches the particular RPM. If the start capacitor is not disconnected, the start winding may continue to receive current from the start capacitor and the run capacitor, and thereby, the start winding may overheat, causing the motor to fail. Accordingly, to disconnect the start capacitor, a Potential Relay (PR) coil and a PR contact connected to the PR coil are used. The PR contact opens based on the voltage across the PR coil, which changes based on the RPM of the motor. Accordingly, when the motor reaches the particular RPM, the voltage across the PR coil increases above a pick-up voltage, and the PR contact opens. The opening of the PR contact disconnects the start capacitor from the stator winding. However, in the overload condition, the temperature of the PR contact increases. The increase in temperature of the PR contact causes latching of the PR contact. The latching in turn causes the start capacitor to remain connected to the start winding even after the motor has reached the particular RPM, eventually leading to the failure of the motor.

[001 1 ] Further, in some cases, to detect the dry run condition of the pump and thereby, to identify the underload condition of the motor, typically, a dry run sensor is used. The dry run sensor may include a dry run probe and may detect the dry run condition when the liquid level falls below a threshold level (which causes the dry run probe to become dry). However, due to the adhesive force between the probes and the liquid, the dry run probes may tend to remain wet despite the liquid level falling below the threshold. Accordingly, accurate detection of the underload condition of the motor may not be possible.

[0012] The present subject matter relates to an integrated pump controller for CSCR motors. With the implementations of the present subject matter, the CSCR motor and the pump may be prevented from getting damaged due to extreme loading conditions.

[0013] In accordance with an example implementation, a motor system includes a motor and an integrated controller to control the motor. The motor may have a stator. The stator may have a first stator winding. The motor system may include a main relay. A run capacitor may be connected in series to the main relay and to the first stator winding to facilitate running of the motor. The motor system may include a start capacitor to facilitate starting of the motor. The start capacitor may be connected to the first stator winding. A QD relay may be connected to the main relay and to the start capacitor. Further, the QD relay and the start capacitor may together be connected in parallel to the run capacitor.

[0014] In an example, the integrated controller may protect the motor from the overload condition and the underload condition based on the power supplied to the motor. For estimating the power supplied, the integrated controller may acquire a plurality of samples of voltage supplied to the motor and a plurality of samples of the current supplied to the motor.

[0015] In an example, if the integrated controller detects that the motor has reached a particular RPM, such as 75 % - 80 % of the rated RPM of the motor and may cause disconnection of the start capacitor from the first stator winding by switching of the QD relay. As a voltage across the start winding is indicative of the RPM, the integrated controller may utilize the voltage across the first stator winding for determining whether the motor has reached the particular RPM.

[0016] Upon switching off the QD relay, the motor system may detect the extreme load condition based on a comparison of the estimated power with a first power threshold and with a second power threshold and switch off the main relay upon the detection. For instance, the estimated power being less than a first power threshold indicates the underload condition and the estimated power being higher than a second power threshold indicates the overload condition. The integrated controller may switch off the main relay if the estimated power is less than the first power threshold or if the estimated power is higher than the second power threshold. Accordingly, the motor system facilitates protection of the pump during extreme loading conditions.

[0017] The present subject matter prevents the malfunctioning and failure of the motor system caused due to the extreme load conditions, such as an overload condition and an underload condition. Further, by computing the power supplied to the motor and utilizing the computed power to estimate the extreme load condition, the present subject matter detects the extreme loading conditions instantaneously and prevents a time lag between the occurrence of the extreme loading conditions and the detection.

[0018] The present subject matter eliminates use of separate components, such as the dry run sensor, to detect the underload condition of the motor. Furthermore, by controlling a quick disconnect (QD) relay that is connected to a start capacitor, the present subject matter facilitates a timely disconnection of the start capacitor from a first stator winding when the particular RPM is reached. Therefore, the present subject matter prevents the first stator winding from overheating and the motor from getting damaged. The present subject matter facilitates fast, safe, and efficient protection of the motor.

[0019] The present subject matter is further described with reference to Figs. 1 -3. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.

[0020] Fig. 1 illustrates a motor system 100, in accordance with an implementation of the present subject matter. The motor system 100 may be connected to an input power supply lines 102 and 104 to supply electric current, hereinafter referred to as current, to the motor system 100. The input power supply line may provide an alternating current (AC) supply. The motor system 100 may include a motor 106. The motor 106 may include a stator and a rotor. The stator may include a first stator winding 1 10 and a second stator winding 1 12. The first stator winding 1 10 may be referred to as a start winding and the second stator winding 1 12 may be referred to as a run winding. The second stator winding 1 12 may be connected in parallel to the first stator winding 1 10. The first stator winding 1 10 and the second stator winding 1 12 may be positioned perpendicular to each other on the stator. A pump (not shown in Fig. 1 ) may be coupled to the motor 106 to be driven by the motor 106. In particular, the rotor may be coupled to a shaft of the pump. The pump may pump liquid from a liquid source to another place. For instance, the pump may pump liquid from a well to an overhead tank.

[0021 ] The motor system 100 may include a main relay 1 14 and a quick disconnect (QD) relay 1 16. The main relay 1 14 may be connected between the motor 106 and the input power supply line 102 to control the flow of current to the motor 106. The QD relay 1 16 may be connected to the main relay 1 14. The QD relay 1 16 may receive current from the main relay 1 14 and supply the current to the start winding 1 10. In an example, the main relay 1 14 and the QD relay 1 16 may be solid-state relays mechanical relays, or other types of relays.

[0022] The motor system 100 may include a run capacitor 1 18 to facilitate running of the motor 106. The run capacitor 1 18 may be connected between and in series to the main relay 1 14 and the start winding 1 10. The motor system 100 may include a start capacitor 120 to facilitate starting of the motor 106. Since the motor system 100 includes a start capacitor 120 and a run capacitor 1 18, the motor system 100 may be referred to as a capacitor start capacitor run (CSCR) motor system. The start capacitor 120 may be connected between and in series to the QD relay 1 16 and to the start winding 1 10. Further, the QD relay 1 16 and the start capacitor 120 together may be connected in parallel to the run capacitor 1 18.

[0023] During operation, the run winding 1 12 may receive the current supply from the main relay 1 14. The QD relay 1 16 may receive the current supply from the main relay 1 14 and may supply it to the start capacitor 120, which may provide the current to the start winding 1 10. During starting of the motor 106, the start winding 1 10 may receive the current supply both from the run capacitor 1 18 and the start capacitor 120. The connection of the start winding 1 10 to both the start capacitor 120 and the run capacitor 1 18 may increase a phase difference between current supplied to the start winding 1 10 and that supplied to the run winding 1 10 than a phase difference created by connection of the run capacitor 1 18 alone. The high phase difference creates a rotating magnetic field that rotates the rotor. When the motor 106 reaches a particular RPM, such as a 75 % - 80 % of the maximum RPM of the motor 106, the start capacitor 120 is disconnected from the start winding 1 10 by turning off the QD relay 1 16. The run capacitor 1 18 may remain connected to the start winding 1 10 and facilitates running of the motor 106.

[0024] The motor system 100 may include a controller 124. The controller 124 may be implemented as a microprocessor, a microcomputer, a microcontroller, a digital signal processor, a state machine, a logic circuitry, and/or a device that manipulate signals based on operational instructions. Among other capabilities, the controller 124 may fetch and execute computer-readable instructions stored in a memory (not shown in Fig. 1 ), such as a volatile memory (e.g., RAM) or a non-volatile memory (e.g., EPROM, flash memory, Memristor, etc.), of the controller 124. The controller 124 may be coupled to the main relay 1 14 and to the QD relay 1 16.

[0025] The controller 124 may include an input/ output interface 126. The input/output interface 126 may include a variety of machine-readable instructions-based interfaces and hardware interfaces that allow the controller 124 to interact with different entities of the motor system 100, such as the main relay 1 14 and the QD relay 1 16. Further, the input/output interface 126 may enable the components of the controller 124 to communicate with computing devices, web servers, and external repositories. The interface may facilitate multiple communications within a wide variety of networks and protocol types, including wireless networks, wireless Local Area Network (WLAN), RAN, satellite-based network, etc. [0026] The controller 124 may protect the motor 106 from conditions that may damage the motor 106, such as an overload condition, and an underload condition. In the underload condition, the power supplied to the motor 106 is lower than a rated power range of the motor 106. In the overload condition, the power supplied to the motor 106 is higher than the rated power range. The rated power range may be determined based on a mathematical product of a rated current range and a rated voltage range. The rated voltage range and the rated current range may be a range of voltage and a range of current respectively that the motor 106 is designed for and that the motor 106 should be supplied with for normal operation of the motor 106. In order to protect the motor 106, the controller 124 may acquire samples of voltage A supplied to the motor 106 and current B supplied to the motor 106 based on the plurality of samples of the voltage and the plurality of samples of current, the controller 124 may estimate power supplied to the motor 106. For instance, the controller 124 may determine a root mean square value (RMS) value of the voltage and an RMS value of the current supplied to the motor 106.

[0027] The controller 124 may also cause disconnection of the start capacitor 120 from the start winding 1 10 when the motor 106 reaches the particular RPM. To determine whether the motor 106 has reached the particular RPM, the controller 124 may determine the voltage across the start winding 1 10, as the RPM of the motor 106 changes with change in the voltage across the start winding 1 10. Accordingly, the controller 124 may detect that the motor 106 has reached the particular RPM if the voltage across the start winding 1 10 is higher than a first voltage threshold. The voltage across the start winding 1 10 may be referred hereinafter to as the start winding voltage. In an example, the first voltage threshold may be within the rated voltage range. The rated voltage range may have a second voltage threshold as its lower limit and a third voltage threshold as its upper limit. In an example, the first voltage threshold may be a fraction of the third voltage threshold. In an example, the second voltage threshold may be 180 V and the third voltage threshold may be 250 V. The first voltage threshold may be, for example, 215 V.

[0028] Based on the detection that motor 106 has reached the particular RPM, the controller 124 may disconnect the start capacitor 120 from the start winding 1 10 by switching off the QD relay 1 16. In some cases, the motor 106 may get damaged due to an undervoltage condition or an overvoltage condition. The undervoltage condition may be a condition where the voltage falls below the rated voltage range of the motor 106. The overvoltage condition may be a condition where the voltage is higher than the rated voltage range. The undervoltage condition may result in reduced starting ability of the motor 106, decrease in performance, and reduced efficiency of the motor 106, while the overvoltage may result in overheating of the motor 106 and failure of the motor 106. To protect the motor 106 from the overvoltage condition and the undervoltage condition, the controller 124 may switch off the main relay 1 14 if it detects the overvoltage condition or the undervoltage condition, as will be described with reference to Fig. 3.

[0029] To detect the overload condition and the underload condition, the controller 124 may estimate the power supplied to the motor 106. In an example, the power supplied to the motor 106 may be determined based on the RMS value of the current and the RMS value of the voltage.

[0030] The controller 124 may compare the estimated power with a first power threshold and a second power threshold. The first power threshold may be a lower limit of the rated power range and the second power threshold may be an upper limit of the rated power range. The first power threshold may be determined based on a mathematical product of a first current threshold and the first voltage threshold and the second power threshold may be determined based on a mathematical product of a second current threshold and the second voltage threshold. The first current threshold may be a lower limit of the rated current range and the second current threshold may be an upper limit of the rated current range. The estimated power being less than the first power threshold may indicate the underload condition and the estimated power being higher than the second power threshold may indicate the overload condition. For an ideal operation of the motor 106, the power should be between the first power threshold and the second power threshold. Therefore, the controller 124 may switch off the main relay 1 14 if the estimated power is less than the first power threshold or if the estimated power is more than the second power threshold.

[0031 ] In an example, the controller 124 may display various parameters associated with the operation of the motor 106, such as the values of voltage supplied to the motor 106, and values of current supplied to the motor 106 on a display unit 128 of the motor system 100. The display unit 128 may include, for example, a liquid crystal display (LCD) display, a light emitting diode (LED) display, or the like.

[0032] As mentioned above, the controller 124 may perform functions, including protecting the motor 106 from extreme load conditions, extreme voltage conditions, and displaying of values of the samples of the voltage and the current. Accordingly, the controller 124 may be referred to as the integrated controller.

[0033] Fig. 2 illustrates a method 200 for controlling the motor 106, in accordance with an implementation of the present subject matter. The order in which the method 200 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method 200 or an alternative method. Furthermore, the method 200 may be implemented by processor(s) or computing device(s) through any suitable hardware, non-transitory machine-readable instructions, or a combination thereof. The method 200 may be utilized in the motor system 100. Further, the steps of the methods 200 may be performed by controller 124.

[0034] Referring to the Fig. 2, at block 202, the operation of the controller 124 may be initialized, for example, with the switching on of the motor 106, at block 202. In an example, a first plurality of samples of the current and a first plurality of samples of the voltage per cycle of the input voltage are to be used for an accurate determination of the RMS value of the current and the RMS value of the voltage respectively. The first plurality of samples of the voltage and the first plurality of samples of the current may be, for example, 20. Accordingly, if the input AC voltage has a frequency of 50 Hz, 1000 samples are to be acquired per second. That is, one sample of current and one sample of voltage is to be acquired in each millisecond.

[0035] In this regard, to acquire a sample of the voltage and a sample of the current periodically, at block 204, the controller 124 may determine if a first period has expired. The first period may be, for example, 1 milli second. To determine if the first period has expired, a first interrupt may be utilized. The first interrupt may alert the controller 124 to acquire samples of the current and samples of the voltage periodically, i.e., upon expiry of the first period.

[0036] If the first period has expired, the controller 124 may acquire a sample of the current and a sample of the voltage, at block 206. Further, at block 206, the controller 124 may increment the sample count by one upon acquiring the sample of the voltage and the sample of the current to track the number of samples acquired so far.

[0037] Further, as mentioned earlier, for accurate determination of the RMS value of the voltage and the RMS value of the current, the first plurality of samples of the voltage and the first plurality of samples of the current may be required. Accordingly, at block 208, the controller 124 may determine if the first plurality of samples of the voltage and the first plurality of samples of the current are acquired. To determine if the first plurality of samples of the voltage and the first plurality of samples of the current are acquired, the controller 124 may determine if the sample count equals the first plurality of samples. For instance, if the sample count is 20, the controller 124 may determine that the first plurality of samples of the current and the first plurality of samples of the voltage is acquired. The first plurality of samples of the current and the first plurality of samples of the voltage may be stored in the controller 124.

[0038] In an example, the controller 124 may display the values of the samples of the voltage and the values of the samples of the current on the display unit 128. The display unit 128 may be refreshed at a frequency lesser than the frequency at which the samples are acquired due to the limitations in the refresh rate of the display unit 128. Accordingly, the display unit may be updated periodically with values of the samples of the voltage and the samples of current at a second period, which is based on the refresh rate of the display unit 128. The second period may be greater than the first period. In an example, the second period may be 5 milliseconds. Accordingly, samples may be acquired once in 1 millisecond and the display unit 128 may be refreshed once in 5millisecond. That is, the display unit 128 may display values of five samples of current and five samples of the voltage. To update the display unit 128 periodically, at block 210, the controller 124 may determine if the second period has expired. To determine if the second period has expired, the controller 124 may utilize a second interrupt. If it is determined that the second period has expired, at block 212, the controller 124 may update the display unit 128 with the values of samples of the voltage and the values of samples of the current acquired.

[0039] When the first plurality of samples is acquired, at block 214, the controller 124 may compute the RMS value of the voltage based on the first plurality of samples of the voltage and the RMS value of the current based on the first plurality of samples of the current. Furthermore, the controller 124 may estimate the power based on the RMS value of the voltage and the RMS value of the current. For instance, the controller 124 may compute a product of the RMS value of the current and RMS value of the voltage to obtain the power. Also, at block 214, the controller 124 may reset the sample count for the next cycle.

[0040] As mentioned earlier, the controller 124 may detect the overvoltage condition and the undervoltage condition and may protect the motor 106 by switching off the main relay 1 14 upon the detection. Accordingly, to detect the overvoltage and the undervoltage condition, at block 216, the controller 124 may determine if the obtained RMS value of the voltage is within the rated voltage range. The controller 124 may store the rated voltage range of the motor 106, i.e., the second voltage threshold and the third voltage threshold.

[0041 ] If the RMS value of the voltage is determined to be outside of the rated voltage range, i.e., the RMS value is either higher than the third voltage threshold or lower than the second voltage threshold, at block 218, the controller 124 may switch off the main relay 1 14. This is because, the RMS value of the voltage being higher than the second voltage threshold indicates the overvoltage condition and the RMS value of the voltage being lower than the rated voltage indicates undervoltage condition. By switching off the main relay 1 14, the controller 124 may stop the current supply to the motor 106 and thereby, the motor 106 may be turned off.

[0042] If the RMS value of the voltage is determined to be within the rated voltage range, then the controller 124 may repeat the step at block 214 to compute the RMS value of the voltage based on subsequent samples of voltage to be able to protect the motor 106 whenever the RMS value of the voltage is outside of the rated voltage range.

[0043] Further, the controller 124 may protect the motor 106 from extreme load conditions, such as the overload condition and the underload condition. In an example, to protect the motor 106 from the extreme load condition, the controller 124 may utilize the power supplied to the motor 106, which is computed at block 214.

[0044] At block 220, the controller 124 may determine if the power supplied to the motor 106 is less than the first power threshold. In an example, the controller 124 may determine if the power supplied to the motor 106 is less than the first power threshold for a first time. The first time may be, for example, 15 s. If it is determined that the power is less than the first power threshold, the controller 124 may switch off the main relay 1 14, at block 218, since the power being less than the second power threshold indicates the underload condition. In an example, the first power threshold may be stored in the controller 124. However, if it is determined that the power is higher than the first power threshold, the controller 124 may repeat the step at block 214 to compute the power based on subsequent samples of the current and subsequent samples of the voltage to be able to protect the motor 106 whenever the power is less than the first power threshold.

[0045] Further, at block 222, the controller 124 may determine if the power is higher than the second power threshold. In particular, the controller 124 may determine that the power is higher than the second power threshold for a second time, such as 15 s. If the controller 124 determines that the power is higher than the second power threshold, the controller 124 may switch off the main relay 1 14 to turn off the motor 106, at block 218. This is because the power being high than the second power threshold indicates the overload condition. In an example, the second power threshold may be stored in the controller 124. If the controller 124 determines that the power is less than the second power threshold, the controller 124 may repeat the step at block 214 to compute the power based on subsequent samples of the current and subsequent samples of the voltage to be able to protect the motor 106 whenever the power is higher than the second power threshold.

[0046] Fig. 3 illustrates a method 300 for controlling the motor 106, in accordance with an implementation of the present subject matter. The order in which the method 300 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method 300 or an alternative method. Furthermore, the method 300 may be implemented by processor(s) or computing device(s) through any suitable hardware, non-transitory machine-readable instructions, or a combination thereof. The method 300 may be utilized in the motor system 100. Further, the steps of the method 300 may be performed by controller 124. [0047] At block 302, the controller 124 may receive motor system 100 initialization instruction. The initialization instruction may be, for example, the turning on of the motor 106. In another example, the motor initialization instruction may be an intimation that a time slot in which the motor 106 is to be operated in an automatic mode of the motor 106 has commenced. The automatic mode and the time slot will be explained with reference to blocks 310-314.

[0048] Subsequently, at block 304, the controller 124 may determine the voltage based on a plurality of samples of the voltage. For instance, the controller 124 may determine the RMS value of the voltage based on the first plurality of samples of the voltage, as explained with reference to Fig. 2. The controller 124 may utilize the determined voltage to protect the motor 106 from the overvoltage and undervoltage condition. Accordingly, to protect the motor 106 from the overvoltage and the undervoltage condition, the controller 124 may determine if the RMS value of the voltage is within the rated voltage range, at block 306.

[0049] If it is determined that the RMS value of the voltage is outside of the rated voltage range, the controller 124 may repeat the step at block 304 to determine the RMS value of the voltage based on subsequent samples of voltage. On the other hand, if it is determined that the RMS value of the voltage is within the rated voltage range, the controller 124 may determine a mode of operation of the motor 106, at block 308.

[0050] In an example, the pump may be operated in the automatic mode or a manual mode. In the automatic mode, the pump is to operate within a first time slot. For instance, in the automatic mode, the pump is to operate between a given time slot of the day, such as between 10 AM and 1 1 AM. In such a case, the pump and the motor 106 may automatically turn on at the beginning of the time slot and turn off at the end of the time slot. To keep track of time of operation of the motor 106, the motor system 100 may include a clock coupled to the controller 1 24. In some examples, the clock may be in-built with the controller 124. Further, the time slot in which the motor 106 is to run may be pre-loaded in the controller 124 or the memory, so that the controller 124 may operate the motor 106 in the time slot. In the manual mode, the motor 106 is to run whenever the motor 106 and the pump are turned on.

[0051 ] Since in the auto mode, the motor 106 may operate within the first time slot, the controller 124 may allow operation of the motor 106 only if the time of operation of the motor 106 is within the first time slot. Accordingly, if the mode is determined to be the auto mode, at block 310, the controller 124 may read the time of operation of the motor 106 from the clock and at block 312, the controller 124 may determine if the read time is within the first time slot. If it is determined that the read time is outside of the first time slot, the controller 124 may repeat the step at block 304 to determine the RMS value of the voltage based on subsequent samples of the voltage. Further, it may be determined that the QD relay 1 16 is not to be turned on. If it is determined that the time of operation of the motor 106 is within the first time slot, the controller 124 may switch on the QD relay 1 16, at block 314. If, at block 308, it is determined that the mode of operation is manual mode, the controller 124 may switch on the QD relay 1 16 to start the motor 106. As the QD relay 1 16 is switched on, the start capacitor 120 may receive the power supply from the QD relay 1 16 and may provide the phase difference between the current supplied to the start winding 1 10 and the run winding 1 12 required for starting of the motor 106.

[0052] Upon switching on the QD relay 1 16, at block 316, the controller 124 may wait for a third time interval. Within this third time interval, the QD relay 1 16 may facilitate starting of the motor 106. The third time interval may be, for example, 100 milli second. Further, at block 318, the controller 124 may switch on the main relay 1 14.

[0053] The controller 124 may utilize the start winding voltage to detect that the motor 106 has reached the particular RPM and subsequently disconnect the start capacitor 120 from the start winding 1 10. In this regard, at block 320, the controller 124 may determine if the start winding voltage is higher than the first voltage threshold. If it is determined that the start winding voltage is higher than the first voltage threshold, the QD relay 1 16 is switched off at block 322. This is because the start winding voltage being higher than the first voltage threshold indicates that the motor 106 has reached the particular RPM. By switching off the QD relay 1 16, the current supply to the start capacitor 120 is prevented and thereby, the start capacitor 120 is disconnected from the start winding 1 10. In an example, the first voltage threshold may be stored in the controller 1 16.

[0054] On the other hand, if it is determined that the start winding voltage is less than the first voltage threshold, it may indicate that the motor 106 is yet to reach the particular RPM and therefore, the controller 124 may repeat the block 320 to continuously monitor the start winding voltage. Therefore, the controller 124 may allow the start capacitor 120 to be connected with the start winding 1 10 till the motor 106 RPM picks up.

[0055] Further, upon switching off the QD relay 1 16, the controller 124 may monitor the power supplied to the motor 106 to protect the motor 106 from the overload condition and the underload condition. At block 324, the controller 124 may estimate the power supplied to the motor 106 based on the first plurality of voltage samples and the first plurality of the current samples. Further, at block 326, the controller 124 may determine if the power supplied to the motor 106 is within the threshold ranges, such as between the first power threshold and the second power threshold. If it is determined that the power is outside of the range, i.e., the power being either less than the first power threshold or higher than the second power threshold, the controller 124 may switch off the main relay to turn off the motor 106 at block 328, as explained with reference to block 220 and block 222. On the other hand, if it is determined that the power is within the threshold range, the controller 124 may repeat the step at block 324 to estimate the power based on subsequent samples of the current and subsequent samples of the voltage to be able to protect the motor 106 when the power is higher than the second power threshold or the power is less than the first power threshold.

[0056] Although in the above examples, the motor system 100 is explained with reference to driving a pump, in some examples, the motor system 100 may be coupled to a compressor to drive the compressor.

[0057] The present subject matter facilitates switching off the motor in case of an extreme load condition, such as an overload condition, or an underload condition. Therefore, the present subject matter prevents the malfunctioning of the motor system caused due to the extreme load condition. Further, by utilising the power supplied to the motor as a parameter to estimate the extreme load condition, the present subject matter detects the extreme loading conditions instantaneously and prevents a time lag between the occurrence of the extreme loading conditions and the detection. The present subject matter may eliminate use of separate components, such as the dry run sensor, to detect the underload condition of the motor. Further, by controlling a quick disconnect (QD) relay that is connected to a start capacitor, the present subject matter facilitates a timely disconnection of the start capacitor from a first stator winding when the particular RPM is reached. Therefore, the present subject matter prevents the first stator winding from overheating and the motor from getting damaged. Furthermore, by switching off the motor when voltage supplied to the motor is outside a rated voltage range of the motor, the present subject matter may also facilitate protection of the motor during undervoltage condition and overvoltage condition. The present subject matter facilitates fast, safe, and efficient protection of the motor.

[0058] Although the present subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter.