WO2011062361A2

WO2011062361A2 - Apparatus for controlling single-phase induction motor and method thereof

Info

Publication number: WO2011062361A2
Application number: PCT/KR2010/006440
Authority: WO
Inventors: Gyunam Kim; Sangyoung Kim
Original assignee: Lg Electronics Inc.
Priority date: 2009-11-17
Filing date: 2010-09-17
Publication date: 2011-05-26
Also published as: WO2011062361A3; KR101641234B1; KR20110054476A

Abstract

Disclosed is an apparatus and method for controlling a single-phase induction motor, particularly, an apparatus and method for controlling a single-phase induction motor, capable of rendering the motor strong to variation of an input voltage, protecting the motor from an over-voltage, and starting or driving the motor stably and efficiently even in a low voltage condition, wherein a simplified circuit including switches can be constructed without use of a PTC thermistor or an overload protector and a current phase can be controlled, thereby improving starting capability.

Description

APPARATUS FOR CONTROLLING SINGLE-PHASE INDUCTION MOTOR AND METHOD THEREOF

This relates to a single-phase induction motor, and particularly, to an apparatus for controlling a single-phase induction motor, capable of operating stably and efficiently in an unstable specific voltage area or a low voltage area, and a method thereof.

In general, an induction motor includes a stator with a winding, a permanent magnet, and a rotor made of an aluminum conductor or iron core. The induction motor refers to a device for generating a periodic current change in the winding of the stator and generating a torque at the stator due to a change in a magnetic field responsive to the current change, so as to obtain a rotational force.

The single-phase induction motor, which is a small motor used for home electronics or the like with an output capacity less than 400W, uses commercial power for in-home use, namely, single-phase AC power. The single-phase induction motor is usually used in home electronics, such as fans, air-conditioners, refrigerators, washing machines and the like, and supplies a rotational force required for their fans, rotation wings, compressors and the like.

However, in the single-phase induction motor, if an AC power source applies power to a single-phase winding, an induction current flows; however, magnetic forces generated from conductors at upper and lower portions of the rotor are offset and an alternating magnetic field whose size changes in an axial direction of the winding is merely generated, resulting in impossibility of generating a rotational force. Consequently, the single-phase induction motor needs a starter for starting the same, and is classified into a split-phase type, a shaded coil type, a condenser type, a repulsion type and the like, according to a starter to be installed therein.

FIG. 1 is a schematic circuit view of a typical condenser type single-phase induction motor. As shown in FIG. 1, the single-phase induction motor includes a main winding 20, an auxiliary winding 30, a positive temperature coefficient (PTC) of thermally sensitive resistor (i.e., PTC thermistor) 40 connected to the auxiliary winding 30 in series, and a condenser 50 connected to the PTC thermistor 40 in parallel. Also, the single-phase induction motor may further include an overload protector 70 for preventing overload. The PTC thermistor 40, which is a semiconductor device whose electric resistance is remarkably increased responsive to increase in temperature, functions as a switch. That is, if a rotation speed reaches a preset value of a normal speed, the PTC thermistor 40 opens the auxiliary winding. The condenser 50 increases operation efficiency, such as a power factor of a motor and the like.

If a single-phase AC power source 10 applies power to the motor, an alternative magnetic field is generated in the main winding 20, and the condenser 50 causes the current phase in the auxiliary winding 30 to be 90 ahead. Accordingly, the auxiliary winding 30 generates an auxiliary magnetic field electrically having a 90 phase difference. Hence, the alternating magnetic field generated in the main winding 20 and the auxiliary magnetic field generated in the auxiliary winding 30 are not offset by each other due to the phase difference of the magnetic fields but combined to generate a rotation magnetic field, thereby turning the single-phase induction motor.

The related art single-phase induction motor uses the starter such as the PTC thermistor, and rotates when a starting torque is higher than a load torque. Also, the starting torque is proportional to an applied voltage. In the related art single-phase induction motor, if an applied voltage is low or a load is high, the single-phase induction motor cannot be started and simultaneously problematically generate a current 10 times as great as a rated current in the winding of the motor. That is, the related art single-phase induction motor has problems that the motor is damaged due to a start failure at a low voltage and an abnormal operation occurs in an application device with the motor.

Furthermore, the PTC thermistor cannot control a time to open the auxiliary winding, and the single-phase induction motor employing the PTC thermistor causes such problems of the start failure at the low voltage area and the abnormal operation.

Therefore, to solve those problems of the related art, an object of the disclosures is to provide an apparatus for controlling a single-phase induction motor, capable of rendering the single-phase induction motor strong to variation of an input voltage, protecting the single-phase induction motor itself from an over-voltage, and stably efficiently driving the single-phase induction motor even in a low voltage condition, and a method thereof.

Another object of the disclosures is to provide an apparatus for controlling a single-phase induction motor, capable of driving the single-phase induction motor by employing a simple circuit construction without use of a PTC thermistor or an overload protector, and a method thereof.

Another object of the disclosures is to provide an apparatus for controlling a single-phase induction motor, capable of detecting an input voltage of the single-phase induction motor and driving the single-phase induction motor based upon the detected input voltage, and a method thereof.

To achieve these and other advantages and in accordance with the purpose of the disclosures, as embodied and broadly described herein, there is provided an apparatus for controlling a single-phase induction motor, the apparatus including a main winding switch connected to a main winding in series and configured to apply power to the main winding or block power applied thereto, an auxiliary winding switch connected to an auxiliary winding in series and configured to apply power to the auxiliary winding or block power applied thereto, a detector configured to detect an input voltage from an external power source and detect a zero-cross point of the input voltage, and a controller configured to open or close the main winding switch and the auxiliary winding switch on the basis of the zero-cross point. Here, the controller may connect the main winding switch after a preset time elapses on the basis of the zero-cross point.

The apparatus may further include a power supply unit configured to convert the input voltage into a driving voltage of the controller for output. The power supply unit may include a rectifying unit configured to rectify the input voltage, a smoothing unit configured to smooth the rectified voltage, and a converting unit configured to convert the smoothed voltage into the driving voltage of the controller.

In the apparatus for controlling the single-phase induction motor according to the disclosures, the controller may open the auxiliary winding switch if the detected voltage is higher than or equal to a preset reference voltage, so as to drive the motor via the main winding. Also, the controller may open the main winding switch if the detected voltage is lower than the reference voltage, so as to drive the motor via the auxiliary winding.

In the apparatus for controlling the single-phase induction motor according to the disclosures, the controller may preset a first reference voltage and a second reference voltage higher than the first reference voltage, wherein if the detected voltage is higher than or equal to the second reference voltage, the controller may open the auxiliary winding switch to drive the motor via the main winding. Also, the controller may open the main winding switch if the detected voltage is lower than or equal to the first reference voltage, so as to drive the motor via the auxiliary winding.

To achieve the objects of the disclosures, there is provided a method for controlling a single-phase induction motor including, applying power to the single-phase induction motor via an auxiliary winding switch, detecting a zero-cross point of a voltage applied to the single-phase induction motor, delaying a connection of a main winding switch for a preset time based upon the zero-cross point, and starting the single-phase induction motor. Here, the starting of the single-phase induction motor may include applying a current to the single-phase induction motor via the main winding switch after the delay for the preset time, wherein the single-phase induction motor is started via the main winding switch and the auxiliary winding switch.

The method may further include detecting a voltage applied to the single-phase induction motor, and opening or closing the main winding switch or the auxiliary winding switch based upon the detected voltage, to drive the single-phase induction motor.

In the method for controlling the single-phase induction motor according to the disclosures, the driving of the single-phase induction motor may include setting a reference voltage, comparing the detected voltage with the reference voltage, and opening the auxiliary winding switch if the detected voltage is higher than or equal to the reference voltage according to the comparison result. Also, the driving of the single-phase induction motor may further include opening the main winding switch if the detected voltage is lower than the reference voltage according to the comparison result.

In the method for controlling the single-phase induction motor according to the disclosures, the driving of the single-phase induction motor may include setting a first reference voltage and a second reference voltage higher than the first reference voltage, comparing the detected voltage with the second reference voltage, and opening the auxiliary winding switch if the detected voltage is higher than or equal to the second reference voltage. Also, the driving of the single-phase induction motor may further include comparing the detected voltage with the first reference voltage, and opening the main winding switch if the detected voltage is lower than or equal to the first reference voltage.

The method may further include opening the main winding switch and the auxiliary winding switch if it is determined that the detected voltage is out of a preset operation area range.

In accordance with the apparatus and method for controlling the single-phase induction motor of the disclosures, the single-phase induction motor can be strong to variation of the input voltage and started or driven stably and efficiently even in a low voltage condition. Also, the apparatus for controlling the single-phase induction motor according to the disclosures can protect the motor itself from an over-voltage.

The disclosures can construct a simplified circuit including switches without use of a PTC thermistor or an overload protector and control a current phase, thereby improving starting capability.

The foregoing and other objects, features, aspects and advantages of the disclosures will become more apparent from the following detailed description of the disclosures when taken in conjunction with the accompanying drawings.

The accompanying drawings, which are included to provide a further understanding of the disclosures and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosures and together with the description serve to explain the principles of the disclosures.

In the drawings:

FIG. 1 is a schematic circuit view of a typical condenser-type single-phase induction motor;

FIG. 2 is a schematic block diagram of a single-phase induction motor in accordance with the disclosures;

FIG. 3 is a graph showing a phase control in an apparatus and method for controlling the single-phase induction motor in accordance with the disclosures;

FIG. 4 is a graph showing the start change responsive to the phase control of FIG. 3;

FIG. 5 is a graph showing changes in an operation mode responsive to the change in an input voltage in the single-phase induction motor in accordance with the disclosures; and

FIGS. 6 to 8 are flowcharts each showing a method for controlling a single-phase induction motor in accordance with embodiments of the disclosures.

Description will now be given in detail of an apparatus for controlling a single-phase induction motor and a method thereof in accordance with the preferred embodiments of the disclosures, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated.

Referring to FIG. 2, an apparatus for controlling a single-phase induction motor according to the disclosures may include a main winding switch 230 connected to a main winding 210 in series and configured to apply power to the main winding 210 or block power applied thereto, an auxiliary winding switch 240 connected to an auxiliary winding 220 in series and configured to apply power to the auxiliary winding 220 or block power applied thereto, a detector 500 configured to detect an input voltage applied from an external power source 100 and detect a zero-cross point of the input voltage, and a controller 300 configured to open or close the main winding switch 230 and the auxiliary winding switch 240 based upon the zero-cross point. Here, the controller 300 may connect the main winding switch 230 after a preset time elapses on the basis of the zero-cross point. Also, the control apparatus may further include an operation capacitor 250 connected in parallel to the auxiliary winding switch 240 for compensating a power factor. The control apparatus may enhance an operation efficiency of the single-phase induction motor by virtue of the operation capacitor 250. Alternatively, the operation capacitor 250 may be connected to the main winding switch 230 in parallel if needed.

The main winding switch 230 and the auxiliary winding switch 240 may be configured by employing mechanical or electric semiconductor devices, such as a relay or a triac, respectively. Specifically, the triac is a bi-directional thyristor, namely, an electric device, which performs the same function as two silicon control rectifying units (SCRs) being connected in parallel. The triac is highly reliable in aspect that it can perform a switching operation many number of times.

The detector 500 may be configured as a circuit including OP-AMP and the like, to directly detect an alternating current (AC) voltage applied from the external power source 100 to transfer to the controller 300. The external power source 100 is a commercial AC power source for in-home use. For example, 220V/50Hz AC power source is used in Korea. Also, the detector 500 may detect a zero crossing of the input voltage to send to the controller 300. Alternatively, the detector 500 may detect an input current and then detect a zero-crossing of the input current to send to the controller 300.

The apparatus according to the disclosures may further include a power supply unit 400 for converting the input voltage into a driving voltage of the controller 300 for output. The power supply unit 400 may include a rectifying unit for rectifying the input voltage, a smoothing unit for smoothing the rectified voltage, and a converting unit for converting the smoothed voltage into a driving voltage of the controller 300.

The power supply unit 400 may receive power, namely, commercial AC power, from the external power source 100, and output a direct current (DC) voltage for driving circuits, units and the like, which construct the single-phase induction motor and the control apparatus. In general, a switched-mode power supply (SMPS) is used as the power supply unit 400. Alternatively, a different type of AC-DC converter may be used other than the SMPS. The SMPS may convert an AC voltage of the external power source 100, which has been rectified and then smoothed, into a DC voltage. The SMPS then generates driving voltages, which are needed for the single-phase induction motor and the control apparatus of the single-phase induction motor, by use of a converting unit, such as a high frequency transformer, a regulator or the like. The voltage detector 500 may detect an AC voltage of a commercial AC power source.

FIG. 3 is a graph illustrating a phase control in the apparatus for controlling the single-phase induction motor in accordance with the disclosures, and FIG. 4 is a graph illustrating a start change in response to the phase control of FIG. 3.

Referring to FIGS. 3 and 4, the apparatus for controlling the single-phase induction motor detects a zero-cross point of an input voltage and then applies a current to the single-phase induction motor via the main winding switch 230 after a preset time elapses from the zero-cross point. That is, the controller 300 opens the main winding switch 230 for a preset time on the basis of the zero-crossing of the input voltage detected by the detector 500, thereby delaying the current applied to the main winding 210. Referring to FIG. 4, a starting capability of the single-phase induction motor is in proportion to a main winding current, an auxiliary winding current and the multiple of a phase difference between the main winding current and the auxiliary winding current. Here, a phase control is conducted for the main winding. Accordingly, if a current flowing on the main winding becomes smaller, a phase difference between the main winding current and the auxiliary winding current is increased due to the phase delay of the main winding current, resulting in improvement of the starting capability.

If the detected voltage is higher than or equal to a preset upper limit VH or lower than or equal to a preset lower limit VL, the controller 300 opens both the main winding switch 230 and the auxiliary winding switch 240. Referring to FIG. 5, the controller 300 presets the upper limit VH, such that if the detected voltage is higher than or equal to the upper limit VH, the controller 300 opens both the main winding switch 230 and the auxiliary winding switch 240 so as to block power input to the single-phase induction motor, thereby preventing damage on the single-phase induction motor due to an over-voltage. Also, the controller 300 presets the lower limit VL, such that if the detected voltage is lower than or equal to the lower limit VL, the controller 300 opens both the main winding switch 230 and the auxiliary winding switch 240 so as to block power input to the single-phase induction motor, thereby preventing a start failure due to a low voltage and execution of an abnormal operation due to an over-current being applied to the single-phase induction motor. The controller 300 may further include a storage unit (not shown).The upper limit VH and the lower limit VL may be preset and stored in the storage unit. The upper limit VH and the lower limit VL may be variously set depending on a voltage condition in an area using the single-phase induction motor, type and shape of the single-phase induction motor, a load condition and the like. The upper limit VH and the lower limit VL may be set at the rate of the input voltage from the external power source.

In the meantime, if the detected voltage is lower than the upper limit VH and higher than the lower limit VL, the controller 300 connects both the main winding switch 230 and the auxiliary winding switch 240 to start the single-phase induction motor. Still referring to FIG. 5, if the detected voltage is in an operation area, the controller 300 connects (closes) both the main winding switch 230 and the auxiliary winding switch 240 to start the single-phase induction motor. The controller 300 applies power respectively to the main and

auxiliary windings

210 and 220 to generate an alternating magnetic field from the main winding 210 and an auxiliary magnetic field from the auxiliary winding 220, thereby creating a rotation magnetic field. The single-phase induction motor may turn by virtue of the rotation magnetic field.

If the detected voltage is higher than or equal to a preset reference voltage, the controller 300 opens the auxiliary winding switch 240 to drive the motor via the main winding 210. On the other hand, if the detected voltage is lower than the preset reference voltage, the controller 300 opens the main winding switch 230 to drive the motor via the auxiliary winding 220. The reference voltage may be variously set depending on a voltage condition in an area using the single-phase induction motor, type and shape of the single-phase induction motor, a load condition and the like. The reference voltage may be set at the rate of the input voltage from the external power source.

Still referring to FIG. 5, the controller 300 presets a first reference voltage V1 and a second reference voltage V2. If the detected voltage is higher than or equal to the second reference voltage V2, the controller 300 opens the auxiliary winding switch 240 to drive the motor via the main winding 210. If the detected voltage is lower than or equal to the first reference voltage V1, the controller 300 opens the main winding switch 230 to drive the motor via the auxiliary winding 220. The first and second reference voltages V1 and V2 may be variously set depending on a voltage condition in an area using the single-phase induction motor, type and shape of the single-phase induction motor, a load condition and the like. The first and second reference voltages V1 and V2 may be set at the rate of the input voltage from the external power source. The controller 300 may execute a hysteresis operation using the first and second reference voltages V1 and V2, which have an approximately 10V difference therebetween, thereby preventing the damage on the motor caused due to a drastic variation of the input voltage.

Also, the controller 300 may calculate a start time based upon the detected voltage. If the start time based upon the detected voltage elapses after starting the single-phase induction motor, the controller 300 may open one of the switches to drive the single-phase induction motor.

In the apparatus for controlling the single-phase induction motor according to the disclosures, the detector 500 may be connected to the smoothing unit of the power supply unit 400 so as to detect an AC voltage smoothed by the smoothing unit. That is, the detector 500 detects a voltage output from the smoothing unit using resistance by way of a voltage distribution, and then sends the detected voltage to the controller 300. The controller 300 may thusly drive the single-phase induction motor based upon the voltage output from the smoothing unit.

Referring to FIG. 6, a method for controlling a single-phase induction motor according to the disclosures may include applying power to the single-phase induction motor via the auxiliary winding switch (S110), detecting a zero-cross point of the voltage applied to the single-phase induction motor (S120), delaying connection of the main winding switch for a preset time based upon the zero-cross point (S130), and starting the single-phase induction motor (S150). Here, the step S150 of starting the single-phase induction motor may include applying a current to the single-phase induction motor via the main winding switch after the delay for the preset time (S140), thereby starting the single-phase induction motor via the main winding switch and the auxiliary winding switch. Hereinafter, the construction of the apparatus will be understood with reference to FIG. 2.

Referring back to FIGS. 3 and 4, according to the method for controlling the single-phase induction motor, a zero-cross point of an input voltage is detected, and a current is applied to the single-phase induction motor after a preset time elapses from the zero-cross point. That is, the main winding switch 230 is open for a preset time based upon the zero-crossing of the detected input voltage, thereby delaying the current applied to the main winding 210. Further referring to FIG. 4, the starting capability of the single-phase induction motor is in proportion to the main winding current, the auxiliary winding current and the multiple of a phase difference between the main winding current and the auxiliary winding current. Here, a phase control is conducted for the main winding. Accordingly, if a current flowing on the main winding becomes smaller, a phase difference between the main winding current and the auxiliary winding current is increased due to the phase delay of the main winding current, resulting in improvement of the starting capability.

Referring to FIG. 7, the method for controlling the single-phase induction motor according another embodiment of the disclosures may further include detecting a voltage applied to the single-phase induction motor (S210), and opening or closing the main winding switch or the auxiliary winding switch based upon the detected voltage to drive the single-phase induction motor (S240 to S242).

In the method for controlling the single-phase induction motor according the another embodiment of the disclosures, the step of driving the single-phase induction motor may include setting a reference voltage (not shown), comparing the detected voltage with the reference voltage (S240), and opening the auxiliary winding switch if the detected voltage is higher than or equal to the reference voltage according to the comparison result (S241). Also, the step of driving the single-phase induction motor may further include opening the main winding switch if the detected voltage is lower than the reference voltage (S242).

Still referring to FIG. 7, in the method for controlling the single-phase induction motor according the another embodiment of the disclosures, after detecting a voltage input to the motor (S210), it is determined whether the detected voltage is higher than or equal to a preset upper limit (S220), and determined whether the detected voltage is lower than or equal to a preset lower limit (S224). If the detected voltage is determined to be higher than or equal to the upper limit or lower than or equal to the lower limit, namely, if the detected voltage is out of an operation area range, the main winding switch and the auxiliary winding switch are open to block power input to the main winding and the auxiliary winding (S221 and S222). According to the determination of Steps S220 and S224, if the detected voltage is lower than the upper limit and higher than the lower limit, namely, if the detected voltage is within the operation area range, both the main winding switch and the auxiliary winding switch are connected (closed) to start the motor (S235), and opening or closing the main winding switch or the auxiliary winding switch based upon the detected voltage so as to drive the motor (S240 and the following steps). Hereinafter, the construction of the apparatus will be understood with reference to FIG. 2.

In the method for controlling the single-phase induction motor, a zero-cross point of the input voltage is detected (S232). After a preset time elapses from the zero-cross pint (S233), a current is applied to the single-phase induction motor (S234). That is, the main winding switch 230 is open for a preset time based upon the zero-crossing of the detected input voltage so as to delay a current applied to the main winding 210 (S233). Also, if the detected voltage is higher than or equal to a preset reference voltage, the auxiliary winding switch 240 is open to drive the motor via the main winding 210 (S241). On the other hand, if the detected voltage is lower than the preset reference voltage, the main winding switch 230 is open to drive the motor via the auxiliary winding 220 (S242). The reference voltage may be variously set depending on a voltage condition in an area using the single-phase induction motor, type and shape of the single-phase induction motor, a load condition and the like. The reference voltage may be set at the rate of the input voltage from the external power source.

Referring to FIG. 8, a method for controlling a single-phase induction motor according to another embodiment of the disclosures may include detecting a voltage input to the motor (S310), determining whether the detected voltage is higher than or equal to a preset upper limit (S320), determining whether the detected voltage is lower than or equal to a preset lower limit (S324), opening the main winding switch and the auxiliary winding switch to block power applied to the main winding and the auxiliary winding if the detected voltage is determined to be higher than or equal to the upper limit or lower than or equal to the lower limit, namely, if the detected voltage is out of an operation area range (S321 and S322), connecting (closing) the main winding switch and the auxiliary winding switch to start the motor if the detected voltage is lower than the upper limit or higher than the lower limit, namely, if the detected voltage is within the operation area range, according to the determination of Steps S320 and S324 (S335), and opening or closing the main winding switch or the auxiliary winding switch based upon the detected voltage so as to drive the motor (S340 and the following steps). Hereinafter, the construction of the apparatus will be understood with reference to FIG. 2.

In the method for controlling the single-phase induction motor, a zero-cross point of the input voltage is detected (S332). After a preset time elapses from the zero-cross pint (S333), a current is applied to the single-phase induction motor (S334). That is, the main winding switch 230 is open for a preset time based upon the zero-crossing of the detected input voltage so as to delay a current applied to the main winding 210 (S333). Also, in the control method according to the another embodiment of the disclosures shown in FIG. 8, the step of driving the single-phase induction motor may include setting a first reference voltage and a second reference voltage higher than the first reference voltage (not shown), comparing the detected voltage with the second reference voltage (S340), and opening the auxiliary winding switch if the detected voltage is higher than or equal to the second reference voltage. Also, the step of driving the single-phase induction motor may further include comparing the detected voltage with the first reference voltage (S343), and opening the main winding switch if the detected voltage is lower than or equal to the first reference voltage (S344).

In the driving of the motor, the first reference voltage and the second reference voltage higher than the first reference voltage are preset. Afterwards, the detected voltage is compared with the second reference voltage (S350). If the detected voltage is higher than or equal to the second reference voltage, the auxiliary winding switch is open. Upon opening the auxiliary winding switch, the single-phase induction motor is driven via the main winding (S360). The first and second reference voltages may be variously set depending on a voltage condition in an area using the single-phase induction motor, type and shape of the single-phase induction motor, a load condition and the like. The first and second reference voltages may be set at the rate of the input voltage from the external power source.

In the control method, the operation of consecutively detecting the input voltage to drive the motor is repeated.

Referring back to FIG. 5, the first reference voltage V1 and the second reference voltage V2 are preset. If the detected voltage is higher than or equal to the second reference voltage V2, the auxiliary winding switch is open to drive the motor via the main winding. If the detected voltage is lower than or equal to the first reference voltage, the main winding switch is open to drive the motor via the auxiliary winding. The first and second reference voltages V1 and V2, which have, for example, an approximately 10V difference therebetween, may be used to execute a hysteresis operation, thereby preventing the damage on the motor caused due to a drastic variation of the input voltage.

As described above, in the apparatus and method for controlling the single-phase induction motor according to the disclosures, a switching device, such as a triac, is provided at each of the main winding and the auxiliary winding, a phase-control for a main winding input current is executed after detecting a zero-crossing of an input voltage and the motor is driven based upon the input voltage, whereby the single-phase induction motor can be strong to variation of the input voltage, be started or driven stably and efficiently even in a low voltage area, and be protected from an over-voltage.

Claims

An apparatus for controlling a single-phase induction motor comprising:

a main winding switch connected to a main winding in series and configured to apply power to the main winding or block power applied thereto;

an auxiliary winding switch connected to an auxiliary winding in series and configured to apply power to the auxiliary winding or block power applied thereto;

a detector configured to detect an input voltage from an external power source and detect a zero-cross point of the input voltage; and

a controller configured to open or close the main winding switch and the auxiliary winding switch on the basis of the zero-cross point.
The apparatus of claim 1, wherein the controller connects the main winding switch after a preset time elapses on the basis of the zero-cross point.
The apparatus of claim 2, further comprising a power supply unit configured to convert the input voltage into a driving voltage of the controller for output.
The apparatus of claim 3, wherein the power supply unit comprises:

a rectifying unit configured to rectify the input voltage;

a smoothing unit configured to smooth the rectified voltage; and

a converting unit configured to convert the smoothed voltage into the driving voltage of the controller.
The apparatus of claim 1, wherein the controller opens the auxiliary winding switch if the detected voltage is higher than or equal to a preset reference voltage, so as to drive the motor via the main winding.
The apparatus of claim 5, wherein the controller opens the main winding switch if the detected voltage is lower than the reference voltage, so as to drive the motor via the auxiliary winding.
The apparatus of claim 1, wherein the controller presets a first reference voltage and a second reference voltage higher than the first reference voltage,

wherein if the detected voltage is higher than or equal to the second reference voltage, the controller opens the auxiliary winding switch to drive the motor via the main winding.
The apparatus of claim 7, wherein the controller opens the main winding switch if the detected voltage is lower than or equal to the first reference voltage, so as to drive the motor via the auxiliary winding.
A method for controlling a single-phase induction motor comprising:

applying power to the single-phase induction motor via an auxiliary winding switch;

detecting a zero-cross point of a voltage applied to the single-phase induction motor;

delaying a connection of a main winding switch for a preset time based upon the zero-cross point; and

starting the single-phase induction motor.
The method of claim 9, wherein starting of the single-phase induction motor comprises:

applying a current to the single-phase induction motor via the main winding switch after the delay for the preset time,

wherein the single-phase induction motor is started via the main winding switch and the auxiliary winding switch.
The method of claim 9, further comprising:

detecting a voltage applied to the single-phase induction motor; and

opening or closing the main winding switch or the auxiliary winding switch based upon the detected voltage, to drive the single-phase induction motor.
The method of claim 11, wherein driving of the single-phase induction motor comprises:

setting a reference voltage;

comparing the detected voltage with the reference voltage; and

opening the auxiliary winding switch if the detected voltage is higher than or equal to the reference voltage according to the comparison result.
The method of claim 12, wherein driving of the single-phase induction motor further comprises:

opening the main winding switch if the detected voltage is lower than the reference voltage according to the comparison result.
The method of claim 11, wherein driving of the single-phase induction motor comprises:

setting a first reference voltage and a second reference voltage higher than the first reference voltage;

comparing the detected voltage with the second reference voltage; and

opening the auxiliary winding switch if the detected voltage is higher than or equal to the second reference voltage.
The method of claim 14, wherein driving of the single-phase induction motor further comprises:

comparing the detected voltage with the first reference voltage; and

opening the main winding switch if the detected voltage is lower than or equal to the first reference voltage.
The method of claim 11, further comprising:

opening the main winding switch and the auxiliary winding switch if it is determined that the detected voltage is out of a preset operation area range.