System and method for magnetizing a transformer in an electrical system prior to energizing the electrical system

• US 10,326,395 B2
• Filed: 10/21/2015
• Issued: 06/18/2019
• Est. Priority Date: 12/15/2014
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Inventors: Gibbs, Irving A., Farr, Thomas A., Schueneman, Ron C.
• Primary Examiner(s): Glass, Erick D
• Application Number:
  US15/534,508
• Publication Number:
  US 20170338760A1
• Time in Patent Office: 1,336 Days
• CPC Class Codes: H02H 1/043 to inrush currents H02H1/046 takes precedence; differential protection of transformers H02H7/045
• CPC Class Codes: H02H 7/04 for transformers
• CPC Class Codes: H02H 9/002 limiting inrush current on switching on of inductive loads subjected to remanence, e.g. transformers
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 1/40 Means for preventing magnetic saturation
• CPC Class Codes: H02P 1/16 for starting dynamo-electric motors or dynamo-electric converters
• CPC Class Codes: H02P 13/12 by varying magnetic bias
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence

Abstract

An electrical system (2) includes a transformer (16) coupled to an AC source (6) that provides a main AC voltage, the transformer having a number of sets of primary windings (18) and secondary windings (20), and a charging module (32) structured to generate a magnetizing AC voltage. The charging module is structured to selectively provide the magnetizing AC voltage to: (i) one of the number of sets primary windings, or (ii) one of the number of sets secondary windings. The magnetizing AC voltage is such that responsive to the magnetizing AC voltage being provided to one of the sets of primary windings or one of the sets of secondary windings, one or more of the sets of primary windings will be magnetized in a manner wherein a flux of the one or more of the number of primary windings is in phase with the main AC voltage provided from the AC source.

Claims

1. An electrical system, comprising:

a transformer structured to be selectively coupled to an AC source that provides a main AC voltage having a main AC voltage level, the transformer having a number of windings; and

a charging module structured to be selectively coupled to the AC source that provides the main AC voltage to receive the main AC voltage having the main AC voltage level and to generate a magnetizing AC voltage in response to receiving the main AC voltage having the main AC voltage level from the AC source, wherein the charging module is structured to selectively provide the magnetizing AC voltage to the transformer, wherein the magnetizing AC voltage is such that responsive to the magnetizing AC voltage being provided to the transformer one or more of the windings will be magnetized in a manner wherein a voltage of the one or more of the windings is in phase with the main AC voltage provided from the AC source to eliminate or reduce in-rush current into the transformer.

2. The electrical system according to claim 1, wherein the number of windings comprises a number of sets of first windings and a number of sets of second windings, wherein the charging module is structured to selectively provide the magnetizing AC voltage to:

(i) one of the number of sets first windings, or (ii) one of the number of sets second windings.

3. The electrical system according to claim 1, wherein the charging module comprises an auxiliary transformer (32) structured to be selectively coupled to the transformer.

4. The electrical system according to claim 3, wherein the auxiliary transformer is structured to be selectively coupled to the transformer through an auxiliary contactor.

5. The electrical system according to claim 4, wherein the transformer is a 3-phase phase shifting wye-delta transformer and the auxiliary transformer is a 3-phase shifting delta-wye transformer.

6. The electrical system according to claim 1, wherein the transformer is structured to be selectively coupled to the AC source through a main contactor.

7. The electrical system according to claim 1, wherein the electrical system is a variable frequency drive system, and wherein the transformer is an isolation transformer of a variable frequency drive.

8. The electrical system according to claim 1, wherein the number of sets of first windings is a number of sets of primary windings and the number of sets of second windings is a number of sets of secondary windings, wherein the charging module is structured to selectively provide the magnetizing AC voltage to:

(i) one of the number of sets primary windings, or (ii) one of the number of sets secondary windings, wherein the magnetizing AC voltage is such that responsive to the magnetizing AC voltage being provided to one of the number of sets of primary windings or one of the number of sets of secondary windings, one or more of the number of sets of primary windings will be magnetized in a manner wherein a voltage of the one or more of the number of primary windings is in phase with the main AC voltage provided from the AC source.

9. A method of energizing an electrical system, the electrical system including a transformer structured to be selectively coupled to an AC source that provides a main AC voltage having a main AC voltage level, the transformer having a number of windings, the method comprising:

generating a magnetizing AC voltage from the main AC voltage having the main AC voltage level when the number of windings is not coupled to the AC source;

providing the magnetizing AC voltage to the transformer when the number of windings is not coupled to the AC source to magnetize one or more of the windings in a manner wherein a voltage of the one or more of the windings is in phase with the main AC voltage to eliminate or reduce in-rush current into the transformer; and

coupling the windings to the AC source such that the main AC voltage is applied to the windings.

10. The method according to claim 9, further comprising terminating the providing the magnetizing AC voltage before or after coupling the number of windings to the AC source.

11. The method according to claim 9, wherein the generating the magnetizing AC voltage comprises providing the main voltage to an auxiliary transformer, and wherein the providing the magnetizing AC voltage comprises the auxiliary transformer to the transformer when the number of windings is not coupled to the AC source.

12. The method according to claim 11, wherein the transformer is a wye-delta transformer and the auxiliary transformer is a delta-wye transformer.

13. The method according to claim 9, wherein the transformer is an isolation transformer of a variable frequency drive.

14. The method according to claim 9, wherein the number of windings comprises a number of sets of first windings and a number of sets of second windings.

15. The method according to claim 14, wherein the number of sets of first windings is a number of sets of primary windings and the number of sets of second windings is a number of sets of secondary windings.