FREQUENCY CONVERTER START-UP

• US 20100253256A1
• Filed: 04/01/2010
• Published: 10/07/2010
• Est. Priority Date: 04/02/2009
• Status: Active Grant

• Current Assignee: Vacon Oy (Danfoss A/S)
• Original Assignee: Vacon Oyj (Danfoss A/S)
• Inventors: OLLILA, Jaakko, DOKTAR, Andreas, STRANDBERG, Stefan
• Granted Patent: US 8,350,506 B2
• Time in Patent Office: Days
• US Class Current: 318/400.110
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 6/14 Electronic commutators
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position
• CPC Class Codes: H03K 17/06 Modifications for ensuring a fully conducting state

Abstract

Method and apparatus to start a frequency converter equipped with a direct current intermediate circuit, particularly when a permanent magnet motor whose rotor is rotating at the start-up time is connected to it, wherein the frequency converter has a network bridge (10) and load bridge (11), and the load bridge has controllable power semiconductor switches of the upper and lower branch (V₁-V₆) and parallel connected zero diodes (D₁-D₆), and a direct current intermediate circuit between them, and the said frequency converter uses a current transducer placed in the direct current intermediate circuit, and the analogue current signal composed by it features samples of the measured output currents, and the diverter switches of the frequency converter'"'"'s upper branch are controlled using the bootstrap method, wherein start-up is initiated by controlling the controllable power semiconductor switch of the lower branch of at least one output phase to a conductive state for one or several periods of time, preferably of approximately 200 μs, at a time.

Claims

1. A method to start a frequency converter equipped with a direct current intermediate circuit, particularly when a permanent magnet motor whose rotor is rotating at the start-up time is connected to it,

wherein the frequency converter has a network bridge (10) and load bridge (11), and the load bridge has controllable power semiconductor switches of the upper and lower branch (V₁-V₆) and parallel connected zero diodes (D₁-D₆), and a direct current intermediate circuit between them,

and the said frequency converter uses a current transducer placed in the direct current intermediate circuit, and the analogue current signal composed by it features samples of the measured output currents, and

the diverter switches of the frequency converter'"'"'s upper branch are controlled using the bootstrap method,

characterized in that

start-up is initiated by controlling the controllable power semiconductor switch of the lower branch of at least one output phase to a conductive state for one or several periods of time, preferably of approximately 200 μ

s, at a time.

2. Method according to claim 1,

characterized in that

upon the current transducer detecting that the output current deviates from zero during the time between the conductive controls, start-up of the frequency converter is prevented.

3. Method according to claim 1,

characterized in that

upon the current transducer detecting that the output current deviates from zero during the time between the conductive controls, the conductive controls are continued until there is no current flow.

4. Method according to claim 1,

characterized in that

the time during which flow of current is detected is used as the indicator of the positive alternation of the phase voltage of the rotating permanent magnet motor.

5. Method according to claim 1,

characterized in that

controls of the lower branch'"'"'s controllable power semiconductor switches are performed in at least two phases.

6. Method according to claim 5,

characterized in that

the times during which current is detected to flow in at least two phases whose controllable lower branch power semiconductor switches are controlled are used as an indicator of the phase sequence of the rotating permanent magnet motor.

13. Method according to claim 3,

characterized in that

the time during which flow of current is detected is used as the indicator of the positive alternation of the phase voltage of the rotating permanent magnet motor.

14. Method according to claim 3,

characterized in that

controls of the lower branch'"'"'s controllable power semiconductor switches are performed in at least two phases.

15. Method according to claim 4,

characterized in that

controls of the lower branch'"'"'s controllable power semiconductor switches are performed in at least two phases.

7. An apparatus to start a frequency converter equipped with a direct current intermediate circuit, particularly when a permanent magnet motor whose rotor is rotating at the start-up time is connected to it,

wherein the frequency converter has a control unit, network bridge (10) and load bridge (11), and the load bridge has controllable power semiconductor switches of the upper and lower branch (V₁-V₆) and parallel connected zero diodes (D₁-D₆), and a direct current intermediate circuit between them,

and the said frequency converter has a current transducer placed in the direct current intermediate circuit, and the analogue current signal composed by it features samples of the measured output currents, and

the said control unit is adapted to control the diverter switches of the frequency converter'"'"'s upper branch with the bootstrap method,

characterized in that

the control unit is adapted to initiate start-up by controlling the controllable power semiconductor switch of the lower branch of at least one output phase to a conductive state for one or several periods of time, preferably of approximately 200 μ

s is at a time.

8. Apparatus according to claim 7,

characterized in that the control unit is adapted so that

upon the current transducer detecting that the output current deviates from zero during the time between the conductive controls, the start-up of the frequency converter is prevented.

9. Apparatus according to claim 7,

characterized in that the control unit is adapted so that

upon the current transducer detecting that the output current deviates from zero during the time between the conductive controls, the conductive controls are continued until there is no current flow.

10. Apparatus according to claim 7,

characterized in that the control unit is adapted so that

the time during which flow of current is detected flow is used as the indicator of the positive alternation of the phase voltage of the rotating permanent magnet motor.

11. Apparatus according to claim 7,

characterized in that the control unit is adapted so that

controls of the lower branch'"'"'s controllable power semiconductor switches are performed in at least two phases.

12. Apparatus according to claim 11,

characterized in that the control unit is adapted so that

the times during which current is detected to flow in at least two phases whose controllable lower branch power semiconductor switches are controlled are used as an indicator of the phase sequence of the rotating permanent magnet motor.

16. Apparatus according to claim 9,

characterized in that the control unit is adapted so that

the time during which flow of current is detected flow is used as the indicator of the positive alternation of the phase voltage of the rotating permanent magnet motor.

17. Apparatus according to claim 9,

characterized in that the control unit is adapted so that

controls of the lower branch'"'"'s controllable power semiconductor switches are performed in at least two phases.

18. Apparatus according to claim 10,

characterized in that the control unit is adapted so that

controls of the lower branch'"'"'s controllable power semiconductor switches are performed in at least two phases.