METHOD AND SYSTEM TO START MULTIPLE AC MOTORS SUPPLIED BY A POWER CONVERTER VIA A COMMON AC BUS

• US 20100164412A1
• Filed: 03/14/2007
• Published: 07/01/2010
• Est. Priority Date: 03/14/2007
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited (Hitachi, Ltd.)
• Original Assignee: ABB Technology AG (ABB Limited)
• Inventors: Harnefors, Lennart
• Granted Patent: US 8,330,398 B2
• Time in Patent Office: Days
• US Class Current: 318/102
• CPC Class Codes: H02P 1/58 sequentially
• CPC Class Codes: H02P 25/034 Voice coil motors voice coil motors driven by DC power H02P7/025
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence

Abstract

A method to start at least two AC motors that are supplied from a common AC bus, which in turn is supplied from a power converter. At least one of the AC motors is an electrically excited synchronous motor including an excitation circuit. The synchronous motor is started first. During starting of remaining of the at least two AC motors a reactive power supplied by the power converter is determined and an increase of a field current or of a field voltage of the synchronous motor in linear dependence on the reactive power supplied by the power converter is determined. The increased field current or field voltage is applied to the excitation circuit of the synchronous motor.

Claims

1. A method to start at least two AC motors which are supplied from a common AC bus which in turn is supplied from a power converter, wherein at least one of the AC motors is an electrically excited synchronous motor comprising an excitation circuit, the method comprising:

starting first the synchronous motor,

during starting of remaining of the at least two AC motors

determining a reactive power supplied by the power converter,

determining an increase of a field current or of a field voltage of the synchronous motor in linear dependence on the reactive power supplied by the power converter, and

applying the increased field current or field voltage to the excitation circuit of the synchronous motor.

2. The method according to claim 1, further comprising:

determining an output current of the power converter and reducing an output voltage of the power converter when the output current reaches a first predetermined limit.

3. The method according to claim 2, further comprising:

reducing an output frequency of the power converter when the output current reaches a second predetermined limit.

4. The method according to claim 1, where the method is only applied during starting of remaining at least two AC motors.

5. A system, comprising:

at least two AC motors, wherein at least one of the motors is an electrically excited synchronous motor comprising an excitation circuit,

a common AC bus to supply the at least two AC motors,

a power converter to supply the common AC bus, and

a first control unit to control the excitation circuit, wherein the first control unit

starts the first synchronous motor, and

during starting of remaining of the at least two AC motors

determines an increase of a field current or of a field voltage of the synchronous motor in linear dependence on the reactive power supplies by the power converter, and

applies the increased field current or field voltage to the excitation circuit of the synchronous motor.

6. The system according to claim 5, further comprising:

a second control unit to control an output of the power converter, wherein the second control unit determines an output current of the power converter and reduces an output voltage of the power converter when the output current reaches a first predetermined limit.

7. The system according to claim 6, wherein the second control unit reduces an output frequency of the power converter when the output current reaches a second predetermined limit.

8. The system according to claim 5, wherein the at least two AC motors are three-phase AC motors.

9. The system according to claim 5, wherein the system comprises a part of an offshore installation.