Drive circuit for a permanent magnet motor

Patent metadata

Field	Value
Publication number	US-10211762-B2
Application number	US-201514822292-A
Country	US
Kind code	B2
Filing date	Aug 10, 2015
Priority date	Aug 8, 2014
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

A drive circuit for an electric motor having a wound stator and a permanent magnet rotor, includes a controllable bidirectional AC switch connected in series with a stator winding between two terminals for connecting to an AC power supply. First and second position sensors detect the position of magnetic poles of the rotor. A voltage regulating circuit is connected between the two terminals and the controllable bidirectional AC switch and configured to supply power to the first sensor during the positive cycle and to the second position sensor during the negative cycle of the AC power supply such that the controllable bidirectional AC switch is switched between a conductive state and a non-conductive state in a preset manner, thus enabling the stator to rotate the rotor in only one predetermined direction during start-up.

First claim

The invention claimed is:

1. A drive circuit for an electric motor comprising a stator and a permanent magnet rotor rotatable with respect to the stator, the stator comprising a stator core and a stator coil wound on the stator core, the drive circuit comprising:
a controllable bidirectional AC switch connected in series with the stator coil between two terminals for connecting to an AC power supply;
a first position sensor and a second position sensor for detecting positions of the magnetic poles of the permanent magnet rotor, the first position sensor directly coupled to a control electrode of the controllable bidirectional AC switch via a first unidirectional conductive switch and the second position sensor directly coupled to the control electrode of the controllable bidirectional AC switch via a resistor; and
a voltage regulating circuit connected between the two terminals and the controllable bidirectional AC switch and configured to supply power to the first sensor during a positive cycle of the AC power supply and to the second position sensor during a negative cycle of the AC power supply such that the first and second position sensors alternatively output a signal to the controllable bidirectional AC switch to directly switch the controllable bidirectional AC switch between a conductive state and a non-conductive state in a predetermined manner, thus enabling the stator coil to urge the rotor only in a fixed direction during start-up of the motor, and
wherein the voltage regulating circuit comprises a first zener diode and a second zener diode reversely connected in parallel between two terminals of the AC power supply at least via a first resistor and a second resistor respectively, a positive power supply terminal of the first position sensor is connected to a cathode of the first zener diode, a negative power supply terminal of the second position sensor is connected to an anode of the second zener diode, and a negative power supply terminal of the first position sensor and a positive power supply terminal of the second position sensor are connected to a reference voltage.

2. The drive circuit of claim 1 , wherein the first and second position sensors have identical magnetic field positions with respect to the magnetic poles of the permanent magnet rotor.

3. The drive circuit of claim 2 , wherein a current output end of the first unidirectional conductive switch being connected to a control end of the controllable bidirectional AC switch.

4. The drive circuit of claim 3 , wherein an output end of the first position sensor is connected to a current input end of the first unidirectional conductive switch, and an output end of the second position sensor is connected to the current output end of the first unidirectional conductive switch via a resistor.

5. The drive circuit of claim 1 , wherein the anode of the first zener diode, the cathode of the second zener diode, the negative power supply terminal of the first position sensor and the positive power supply terminal of the second position sensor are all connected to the terminal connected to a neutral wire of the AC power supply.

6. The drive circuit of claim 1 , wherein the voltage regulating circuit further comprises a second unidirectional conductive switch connected in series between the first resistor and the first zener diode, and a third unidirectional conductive switch connected in series between the second resistor and the second zener diode, the current output end of the second unidirectional conductive switch being connected to the cathode of the first zener diode, and the current input end of the third unidirectional conductive switch being connected to the anode of the second zener diode.

7. The drive circuit of claim 1 , further comprising an inverter connected between the first unidirectional conductive switch and the control electrode of the controllable bidirectional AC switch.

8. The drive circuit of claim 7 , further comprising a switch connected in parallel with the phase inverter between the first unidirectional conductive switch and the control electrode of the controllable bidirectional AC switch.

9. The drive circuit of claim 1 , wherein the controllable bidirectional AC switch is a TRIAC.

10. The drive circuit of claim 3 , wherein the unidirectional conductive switch is a diode or a transistor.

11. The drive circuit of claim 1 , wherein the controllable bidirectional AC switch is connected in parallel with the voltage regulating circuit, so that no current flows through the voltage regulating circuit while the controllable bidirectional AC switch is conductive.

12. The drive circuit of claim 1 , wherein a non-uniform air gap is formed between the stator and the permanent magnet rotor, enabling a polar axis of the permanent magnet rotor to have an angular offset with respect to a central axis of the stator when the rotor is at rest.

13. The drive circuit of claim 1 , wherein the permanent magnetic rotor operates at a constant rotational speed of 60f/p during a steady state of the motor, where f is a frequency of the AC power supply and p is the number of pole pairs of the rotor.

14. A drive circuit for an electric motor comprising a stator and a permanent magnet rotor rotatable with respect to the stator, the stator comprising a stator core and a stator coil wound on the stator core, the drive circuit comprising:
a controllable bidirectional AC switch connected in series with the stator coil between two terminals for connecting to an AC power supply;
a first position sensor and a second position sensor for detecting positions of the magnetic poles of the permanent magnet rotor; and
a voltage regulating circuit connected between the two terminals and the controllable bidirectional AC switch and configured to supply power to the first sensor during a positive cycle of the AC power supply and to the second position sensor during a negative cycle of the AC power supply such that the first and second position sensors alternatively output a signal to the controllable bidirectional AC switch to switch the controllable bidirectional AC switch between a conductive state and a non-conductive state in a predetermined manner, thus enabling the stator coil to urge the rotor only in a fixed direction during start-up of the motor; and wherein the voltage regulating circuit comprises a first zener diode and a second zener diode reversely connected in parallel between the two terminals at least via a first resistor and a second resistor respectively, a positive power supply terminal of the first position sensor is connected to a cathode of the first zener diode, a negative power supply terminal of the second position sensor is connected to the anode of the second zener diode, and a negative power supply terminal of the first position sensor and a positive power supply terminal of the second position sensor are connected to a reference voltage.

Assignees

• Johnson Electric Sa
• Johnson Electric Int Ag

Inventors

• Li Yue
• Sun Chi Ping
• Liu Bao Ting
• Wang En Hui
• Xin Fei
• Yeung Shing Hin
• Yang Xiu Wen
• Cui yan yun
• Huang Shu Juan

Classifications

• H02P2207/05

  Synchronous machines, e.g. with permanent magnets or DC excitation · CPC title

• H02P7/066

  using a periodic interrupter, e.g. Tirrill regulator · CPC title

• H02P7/295

  of the kind having one thyristor or the like in series with the power supply and the motor · CPC title

• H02P6/22

  in a selected direction of rotation · CPC title

• H02P1/465 Primary

  for starting an individual single-phase synchronous motor · CPC title