TWI559671B - Exciter circuit of synchronous motor - Google Patents

Description

Excitation motor circuit of synchronous motor

This invention relates to an exciter circuit, and more particularly to an exciter circuit for a synchronous motor.

The difference between a synchronous motor and a non-synchronous motor is that an exciter is added to the rotor of the synchronous motor. When the rotor of the synchronous motor forms a magnetic field, an electromagnetic torque is generated between the magnetic field of the rotor and the rotating magnetic field of the stator to cause the rotor to start rotating. Since the synchronous motor has a fixed speed and a fixed proportional relationship between the rotor speed and the AC voltage of the stator, as long as the load is not higher than the maximum torque, the speed will not be affected by the load, so the synchronous motor is generally used in the factory. Drive system.

Generally, the exciter circuit determines whether the rotor and the stator are close to the synchronous speed according to the alternating current (AC) current induced by the coil, that is, the exciter circuit senses the alternating current of the coil and provides a corresponding voltage through the current sensor. The signal, and the excitation circuit determines whether the rotor and the stator are close to the synchronous speed based on the voltage signal provided by the current sensor. However, current sensors are more costly and less durable, thus affecting the overall cost and durability of the synchronous motor.

The present invention provides an exciter circuit of a synchronous motor that converts an alternating current of a coil into a control signal through a simple circuit to reduce the overall cost of the synchronous motor and improve the overall durability of the synchronous motor.

The excitation circuit of the synchronous motor of the present invention comprises a coil, a rectifying unit, a first switching unit, a first resistor, a first diode, a second switching unit, a second resistor, and a second A diode, a capacitor and a control unit. The rectifying unit is configured to provide a driving voltage. The first switching unit receives the driving voltage and a switching signal to provide a driving voltage to the first end of the coil. The first end of the first resistor is coupled to the first end of the coil. The cathode of the first diode is coupled to the second end of the first resistor, and the anode of the first diode is coupled to the second end of the coil. The second switch unit is coupled between the second end of the first resistor and the second end of the coil, and is controlled to be turned on by a control signal. The first end of the second resistor is coupled to the second end of the first resistor. The anode of the second diode is coupled to the second end of the second resistor. The capacitor is coupled between the cathode of the second diode and the second end of the coil to provide a control signal. The control unit receives the control signal to provide a switching signal.

In an embodiment of the invention, the first switching unit and the second switching unit respectively comprise a step-controlled rectifier.

In an embodiment of the invention, the rectifying unit includes a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, and an eighth Diode. The cathode of the third diode provides a DC drive voltage, and the third diode The anode of the body receives an alternating voltage. The cathode of the fourth diode is coupled to the anode of the third diode, and the anode of the fourth diode is coupled to the second end of the coil. The cathode of the fifth diode is coupled to the cathode of the third diode, and the anode of the fifth diode receives the alternating voltage. The cathode of the sixth diode is coupled to the anode of the fifth diode, and the anode of the sixth diode is coupled to the second end of the coil. The cathode of the seventh diode is coupled to the cathode of the third diode, and the anode of the seventh diode receives the alternating voltage. The cathode of the eighth diode is coupled to the anode of the seventh diode, and the anode of the eighth diode is coupled to the second end of the coil.

In an embodiment of the invention, the exciter circuit of the synchronous motor further includes a power supply circuit coupled to the control unit to provide a system voltage to the control unit.

In an embodiment of the invention, the control unit includes a signal processing circuit and a controller. The signal processing circuit receives the control signal to provide a control reference signal. The controller receives the control reference signal to provide a switching signal.

Based on the above, the exciter circuit of the synchronous motor according to the embodiment of the present invention generates a control signal through the second resistor, the second diode, and the capacitor connected in series, and controls the second switch unit to be turned on according to the phase of the AC voltage of the coil. cutoff. And, a control signal can be provided to the control unit as a basis for judging whether the synchronous motor is synchronized. Thereby, the circuit structure of the synchronous motor can be simplified, the cost of the synchronous motor can be reduced, and the passive component can be substituted for the active component to improve the system reliability.

The above described features and advantages of the invention will be apparent from the following description.

100‧‧‧Synchronous motor excitation circuit

110‧‧‧Rectifier unit

120‧‧‧ coil

130‧‧‧Control unit

131‧‧‧Signal Processing Circuit

133‧‧‧ Controller

140‧‧‧Power circuit

C1‧‧‧ capacitor

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

D5‧‧‧ fifth diode

D6‧‧‧ sixth diode

D7‧‧‧ seventh diode

D8‧‧‧ eighth diode

EDP‧‧‧ rising edge

Ir‧‧‧ Current

R1‧‧‧first resistance

R2‧‧‧second resistance

SCL‧‧‧ control signal

SCR1, SCR2‧‧‧ remote controlled rectifier

SI, SV‧‧‧ waveform

SRC‧‧‧ control reference signal

SSW‧‧‧ switch signal

SW1‧‧‧ first switch unit

SW2‧‧‧Second switch unit

Vac‧‧‧AC voltage

Vcc‧‧‧ system voltage

Vdd‧‧‧DC drive voltage

1 is a system diagram of an exciter circuit of a synchronous motor in accordance with an embodiment of the present invention.

2 is a waveform diagram of an alternating current wave and a control signal in accordance with an embodiment of the present invention.

1 is a system diagram of an exciter circuit of a synchronous motor in accordance with an embodiment of the present invention. Referring to FIG. 1 , in the embodiment, the exciter circuit 100 of the synchronous motor includes, for example, a rectifying unit 110 , a coil 120 , a control unit 130 , a power supply circuit 140 , a first switching unit SW1 , and a second switching unit SW2 . The diode D1, the second diode D2, the first resistor R1, the second resistor R2, and the capacitor C1.

The rectifying unit 110 receives the alternating voltage Vac and provides a direct current driving voltage Vdd. The first switching unit SW1 is coupled to the rectifying unit 110 to receive the DC driving voltage Vdd. The first switching unit SW1 is coupled to the first end of the coil 120 and coupled to the control unit 130 to receive the switching signal SSW. The first switching unit SW1 determines whether to provide the DC driving voltage Vdd to the first end of the coil 120 according to the switching signal SSW.

The first end of the first resistor R1 is coupled to the first end of the coil 120. The cathode of the first diode D1 is coupled to the second end of the first resistor R1, and the anode of the first diode D1 is coupled to the second end of the coil 120. The second switch unit SW2 is coupled between the second end of the first resistor R1 and the second end of the 120 coil, and receives the control signal SCL to be turned on by the control signal SCL. The first end of the second resistor R2 is coupled to the first resistor The second end of R1. The anode of the second diode D2 is coupled to the second end of the second resistor R2. The capacitor C1 is coupled between the cathode of the second diode D2 and the second end of the coil 120, and the capacitor C1 correspondingly provides the control signal SCL to the second switching unit SW2.

The control unit 130 is coupled to the first switch unit SW1 and the capacitor C1 to receive the control signal SCL, and determines the frequency (or duty cycle) of the current Ir flowing through the resistor R1 according to the control signal SCL to determine the stator of the synchronous motor (not drawn) Whether or not the rotor and the rotor (not shown) are synchronized, thereby correspondingly providing the switching signal SSW to the first switching unit SW1. In other words, when the stator (not shown) of the synchronous motor and the rotor (not shown) are synchronized, the control unit 130 turns on the first switching unit SW1 through the switching signal SSW; when the stator (not shown) of the synchronous motor and the rotor ( When not synchronized, the control unit 130 turns off the first switching unit SW1 through the switching signal SSW. The power circuit 140 receives the AC voltage Vac and is coupled to the control unit 130 to provide the system voltage Vcc to the control unit 130.

2 is a waveform diagram of an alternating current wave and a control signal in accordance with an embodiment of the present invention. Referring to FIG. 1 and FIG. 2, when the voltage on the coil 120 is a positive half cycle, the current Ir flowing through the first resistor R1 will be a positive half cycle (as shown by the waveform SI), and the second diode D2 will Passing forward, the voltage on coil 120 will enter capacitor C1 to charge capacitor C1. At this time, the voltage across the capacitor C1 (ie, the voltage level of the control signal SCL) rises to form a rising edge EDP, as indicated by the waveform SV, and the second switching unit SW2 is turned on due to the voltage rising control signal SCL. The loop is formed by the second switching unit SW2 that causes the voltage on the coil 120 to pass through.

When the voltage on the coil 120 is a negative half cycle, the electricity flowing through the first resistor R1 The current Ir will be negative half cycle (as indicated by the waveform SI), while the second diode D2 will be reversed, so that the voltage on the coil 120 does not enter the capacitor C1, so that the capacitor C1 will discharge. Then, when the voltage across the capacitor C1 (that is, the voltage level of the control signal SCL) is too low, as indicated by the waveform SV, the second switching unit SW2 is turned off due to the control signal SCL whose voltage is too low. At this time, the voltage on the coil 120 is formed into a loop through the first diode D1 that is forward-conducting.

According to the above, the exciter circuit 100 does not require the current sensor to set the voltage level of the control signal SCL corresponding to the phase of the AC voltage on the coil 120 to accurately turn on or off the second switching unit SW2. Thereby, the cost of the exciter circuit 100 can be saved, and the reliability of the exciter circuit 100 can be improved by replacing the current sensor with an analog circuit.

In addition, since the voltage level of the control signal SCL periodically forms the rising edge EDP, and the frequency of the rising edge EDP is proportional to the alternating voltage on the coil 120, the control unit 130 can determine the alternating voltage on the coil 120 according to the control signal SCL. The frequency is determined to determine whether the stator (not shown) of the synchronous motor and the rotor (not shown) are synchronized. In other words, the control signal SCL can be used to control the second switching unit SW2 and to the control unit 130 as a basis for determining whether the synchronous motor is synchronized.

Referring to FIG. 1 again, in the embodiment, the rectifying unit 110 is a bridge rectifier, and the AC voltage Vac is an example of a three-phase AC voltage. In other words, the rectifying unit 110 includes, for example, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, and an eighth diode D8. The cathode of the third diode D3 provides a DC drive voltage Vdd, and the anode of the third diode D3 receives AC voltage Vac. The cathode of the fourth diode D4 is coupled to the anode of the third diode D3, and the anode of the fourth diode D4 is coupled to the second end of the coil 120. The cathode of the fifth diode D5 is coupled to the cathode of the third diode D3, and the anode of the fifth diode D5 receives the alternating voltage Vac. The cathode of the sixth diode D6 is coupled to the anode of the fifth diode D5, and the anode of the sixth diode D6 is coupled to the second end of the coil 120. The cathode of the seventh diode D7 is coupled to the cathode of the third diode D3, and the anode of the seventh diode D7 receives the alternating voltage Vac. The cathode of the eighth diode D8 is coupled to the anode of the seventh diode D7, and the anode of the eighth diode D8 is coupled to the second end of the coil 120.

The first switching unit SW1 includes, for example, a controlled rectifier SCR1. The anode of the rectifier rectifier SCR1 is coupled to the rectifying unit 110 to receive the DC driving voltage Vdd, the cathode of the rectifier rectifier SCR1 is coupled to the first end of the coil 120, and the gate of the rectifier rectifier SCR1 is coupled to the control unit 130 to receive the switching signal SSW. . The control unit 130 includes, for example, a signal processing circuit 131 and a controller 133. The signal processing circuit 131 is coupled to the capacitor C1 to receive the control signal SCL and convert the control signal SCL into the control reference signal SRC.

The controller 133 is coupled to the signal processing circuit 131 to receive the control reference signal SRC. Moreover, the controller 133 calculates the frequency of the control reference signal SRC, and determines whether the stator (not shown) of the synchronous motor and the rotor (not shown) are synchronized according to the frequency of the control reference signal SRC. Finally, the controller 133 further provides the switch signal SSW to the first switch signal unit SW1 according to whether the stator (not shown) of the synchronous motor and the rotor (not shown) are synchronized.

Further, when the rotor (not shown) of the synchronous motor and the stator (not It is shown that when the synchronization is close, the frequency of the current Ir is lowered, that is, the frequency of the control reference signal SRC gradually approaches zero. Therefore, when the frequency of the control reference signal SRC is close to the synchronous frequency (for example, 3 Hz), the controller 133 can determine that the rotor (not shown) of the synchronous motor is synchronized with the stator (not shown), and thus can be turned on by the switching signal SSW. The first switching unit SW1 transmits the DC driving voltage Vdd to the coil 120.

The second switching unit SW2 includes, for example, a controlled rectifier SCR2. The anode of the rectifier rectifier SCR2 is coupled to the second end of the first resistor R1, the cathode of the rectifier rectifier SCR2 is coupled to the second end of the coil 120, and the gate of the rectifier rectifier SCR2 is coupled to the capacitor C1 to receive the control signal SCL.

In this embodiment, the controller 133 can be implemented in a hardware manner, but in other embodiments, the controller 133 can be implemented by using a software or a firmware. The embodiment of the present invention is not limited thereto.

In summary, the exciting circuit of the synchronous motor of the embodiment of the present invention generates a control signal through the second resistor, the second diode and the capacitor connected in series, and controls the second switching unit to correspond to the phase of the AC voltage of the coil. Turn on or off. And, a control signal can be provided to the control unit as a basis for judging whether the synchronous motor is synchronized. Thereby, since the second switching unit is controlled by a simple circuit connected in series, no additional control signal is needed, and the system is prevented from being abnormal due to insufficient timing of the supply of the control signal; the control unit determines the synchronous motor by using the control signal. When synchronizing or not, since the control signal is directly supplied to the control unit by the capacitor, the judgment of the control unit is more accurate; since the current sensor is replaced by a series resistor, a diode and a capacitor, the synchronous motor can be simplified. Circuit architecture can also reduce the same The cost of the step motor and the replacement of the active components with passive components can increase system reliability.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Synchronous motor excitation circuit

110‧‧‧Rectifier unit

120‧‧‧ coil

130‧‧‧Control unit

131‧‧‧Signal Processing Circuit

133‧‧‧ Controller

140‧‧‧Power circuit

C1‧‧‧ capacitor

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

D5‧‧‧ fifth diode

D6‧‧‧ sixth diode

D7‧‧‧ seventh diode

D8‧‧‧ eighth diode

Ir‧‧‧ Current

R1‧‧‧first resistance

R2‧‧‧second resistance

SCL‧‧‧ control signal

SCR1, SCR2‧‧‧ remote controlled rectifier

SRC‧‧‧ control reference signal

SSW‧‧‧ switch signal

SW1‧‧‧ first switch unit

SW2‧‧‧Second switch unit

Vac‧‧‧AC voltage

Vcc‧‧‧ system voltage

Vdd‧‧‧DC drive voltage

Claims (5)

An excitation motor circuit of a synchronous motor, comprising: a coil; a rectifying unit for providing a driving voltage; a first switching unit receiving the driving voltage and a switching signal to provide the driving voltage to the first of the coil a first resistor having a first end coupled to the first end of the coil; a first diode having a cathode coupled to the second end of the first resistor and an anode coupled to the second end of the coil a second switching unit coupled between the second end of the first resistor and the second end of the coil and controlled by a control signal; a second resistor coupled to the first end a second end of the first resistor; a second diode having an anode coupled to the second end of the second resistor; a capacitor coupled to the cathode of the second diode and the second end of the coil Providing the control signal; and a control unit receiving the control signal to provide the switch signal. The exciter circuit of the synchronous motor of claim 1, wherein the first switching unit and the second switching unit respectively comprise a controlled rectifier. The exciter circuit of the synchronous motor of claim 1, wherein the rectifying unit comprises: a third diode, wherein the cathode provides the DC driving voltage, and the anode receives the AC voltage; a fourth diode, the cathode of which is coupled to the anode of the third diode, the anode of which is coupled to the second end of the coil; and a fifth diode whose cathode is coupled to the cathode of the third diode The anode receives the alternating voltage; a sixth diode having a cathode coupled to the anode of the fifth diode, an anode coupled to the second end of the coil; and a seventh diode coupled to the cathode a cathode of the third diode, the anode of which receives the alternating voltage; and an eighth diode having a cathode coupled to the anode of the seventh diode and an anode coupled to the second end of the coil. The exciter circuit of the synchronous motor according to claim 1, further comprising a power supply circuit coupled to the control unit to provide a system voltage to the control unit. The exciter circuit of the synchronous motor of claim 1, wherein the control unit comprises: a signal processing circuit that receives the control signal to provide a control reference signal; and a controller that receives the control reference signal To provide the switch signal.