Device, system and method for starting a single-phase induction motor

1. A method of starting a single-phase induction motor, the motor comprising a rotor and a stator ( 50 ), the stator comprising a main winding ( 50 a ) and a starting winding ( 50 b ), the main winding ( 50 a ) and the starting winding ( 50 b ) being energized by means of an alternating voltage source (F), the starting winding ( 50 b ) being selectively activated and deactivated by a starting device ( 100 ) comprising a microprocessor ( 70 ), the method comprising the steps of:

i) energizing the start winding ( 50 b ) and using the microprocessor ( 70 ) to continuously estimate an operating rotation (R 1 ) of the single-phase induction motor throughout its operation through the phase shift between at least two electrical quantities;

ii) using the microprocessor ( 70 ) to measure a first phase shift level (D 1 ) between at least two electrical quantities of the motor along a first stability stage (E 1 );

iii) monitoring the variation of the first phase shift level (D 1 ) according to the increase of the operating rotation (R 1 ) of the single-phase induction motor along the first stability stage (E 1 );

iv) detecting an inflection stage (E inf ) from the first phase shift level (D 1 ) to a second phase shift level (D 2 ), when the operating rotation (R 1 ) of the single-phase induction motor is close to a regime rotation (R 2 );

v) using the microprocessor ( 70 ) to measure the second phase shift level (D 2 ) between at least two electrical quantities of the motor along a second stability stage (E 2 ), after the inflection stage (E inf ) of the first phase shift level (D 1 ); and

vi) de-energizing the start winding ( 50 b ) when the operating rotation (R 1 ) reaches the regime rotation (R 2 ).

2. The method according to claim 1 , wherein the starting device ( 100 ) further comprises a switch ( 60 ) and a zero-crossing detection circuit ( 90 ).

3. The method according to claim 2 , wherein the steps ii) to v) of measuring and monitoring the first phase shift level (D 1 ) and measuring the second phase shift level (D 2 ) between at least two electrical quantities of the motor are performed by means of the zero-crossing circuit ( 90 ) of the start device ( 100 ) and of the microprocessor ( 70 ).

4. The method according to claim 3 , further comprising an intermediate step between steps v) and vi) of determining whether the first phase shift level (D 1 ) is different from the second phase shift level (D 2 ).

5. The method according to claim 2 , wherein the microprocessor 70 sends the command signals to the switch ( 60 ).

6. The method according to claim 5 , wherein the switch ( 60 ) comprises a TRIAC.

7. The method according to claim 5 , wherein the switch ( 60 ) comprises at least one silicon-controlled rectifier.

8. The method according to claim 5 , wherein the switch ( 60 ) remains initially activated before starting of the single-phase induction motor.

9. The method according to claim 1 , wherein the at least two electrical quantities of the motor of the first phase shift level (D 1 ) and the second phase shift level (D 2 ) are selected from a group comprising: input voltage of the alternating voltage source (F), input current of the alternating voltage source (F), voltage in the main winding ( 50 a ), current in the main winding ( 50 a ), voltage in the start winding ( 50 b ) and current in the start winding ( 50 b ), the voltage between the main winding ( 50 a ) and the start winding ( 50 b ).

10. A system of starting a single-phase induction motor, the motor comprising a rotor and a stator ( 50 ), the stator comprising a main winding ( 50 a ) and a start winding ( 50 b ), the main winding ( 50 a ) and the start winding ( 50 b ) being energized by means of an alternating voltage source (F), the start winding ( 50 b ) being selectively activated and de-activated by a starting device ( 100 ), wherein the system is configured to energize the start winding ( 50 b ) and continuously estimating an operating rotation (R 1 ) of the single-phase induction motor throughout its operation through the phase shift between at least two electrical quantities,

the system comprising a microprocessor ( 70 ), the microprocessor ( 70 ) being further configured to measure a first phase shift level (D 1 ) between at least two electrical quantities of the motor along a first stability stage (E 1 ) and to detect an inflection stage (E inf ) from the first phase shift level (D 1 ) to a second phase shift level (D 2 ), when the operating rotation (R 1 ) of the single-phase induction motor is close to a regime rotation (R 2 ), the first phase shift level (D 1 ) varying according to the increase of the operating rotation (R 1 ) of the single-phase induction motor, the system being further configured to measure, by means of the microprocessor ( 70 ), the second phase shift level (D 2 ) between at least two electrical quantities of the motor along a second stability stage (E 2 ), after the inflection stage (E inf ) of the first phase shift level (D 1 ), and configured to de-energize the start winding ( 50 b ) when the operating rotation (R 1 ) reaches a regime rotation (R 2 ).

11. A starting device ( 100 ) for a single-phase induction motor, the motor comprising a rotor and a stator ( 50 ), the stator comprising a main winding ( 50 a ) and a starting winding ( 50 b ), the main winding ( 50 a ) and the starting winding ( 50 b ) being energized by means of an alternating voltage source (F), the starting winding ( 50 b ) being selectively activated and de-activated by the starting device ( 100 ),

the starting device ( 100 ) comprising a microprocessor ( 70 ), the microprocessor ( 70 ) being configured to energize the start winding ( 50 b ) and continuously estimate an operating rotation (R 1 ) of the single-phase induction motor throughout its operation throughout the phase shift between at least two electrical quantities,

the starting device ( 100 ) being further configured to measure, during a first stability phase (E 1 ), the variation of first phase shift level (D 1 ) between at least two electrical quantities of the motor until the first phase shift level (D 1 ) reaches the second phase shift level (D 2 ) along an inflection stage (E inf ), when the operating rotation (R 1 ) of the single-phase induction motor is close to a regime rotation (R 2 ), the first phase shift level (D 1 ) varying according to the increase of the operating rotation (R 1 ) of the single-phase induction motor, and

the starting device ( 100 ) being further configured to measure, by means of the microprocessor ( 70 ), the second phase shift level (D 2 ) between at least two electrical quantities of the motor along a second stability stage (E 2 ), after the inflection stage (E inf ) of the first phase shift level (D 1 ), and

the starting device ( 100 ) de-energizing the start winding ( 50 b ), when the operating rotation (R 1 ) reaches a regime rotation (R 2 ).