Apparatus and methods for minimizing over voltage in a voltage regulator

• US 5,786,684 A
• Filed: 09/16/1996
• Issued: 07/28/1998
• Est. Priority Date: 09/16/1996
• Status: Expired due to Term

• Current Assignee: ABB Incorporated (ABB Limited)
• Original Assignee: ABB Power T&D Co Inc (ABB Limited)
• Inventors: Bapat, Vinod N.
• Primary Examiner(s): Sterrett, Jeffrey L.
• Application Number:
  US08/710,318
• Time in Patent Office: 680 Days
• Field of Search: 323/255, 323/258, 323/301, 323/340, 323/343
• US Class Current: 323/258
• CPC Class Codes: G05F 1/16 combined with discharge tubes or semiconductor devices

Abstract

A solid state voltage regulator and methods therefore are shown to include a transformer having a secondary coil, the secondary coil having a plurality of taps. A first solid state switch is connected between the regulator output and a first tap. The first switch need only have the capability of being turned on in response to a gate signal. A second solid state switch is connected between the regulator output and a second tap. The second switch has the capability of being turned on and turned off in response to gating signals. The output voltage resulting from the second tap is greater than the first tap. A controller, connected to the input, the output, the first switch and the second switch, senses the voltage present at the regulator input and output and generates gating signals in response to the sensed voltage. The voltage regulator may include several switches similar in construction and operation to the first switch. In such a regulator, the second switch is connected to the tap which results in the coil turn ratio yielding the greatest voltage compensation.

Claims

1. A voltage regulator, having an input and an output on which output a desired voltage is to be regulated, said voltage regulator comprising:

a transformer having a secondary coil, said secondary coil having a plurality of taps;

a first solid state switch, connected between said output and a first one of said taps, said first switch having the capability of being turned ON in response to a first gate signal;

a second solid state switch, connected between said output and a second of said taps, said second switch having the capability of being turned ON and turned OFF in response to a second gate signal;

a third solid state switch, connected between said output and a third one of said taps, said third switch having the capability of being turned ON in response to a third gate signal; and

a controller, connected to said input, said output, said first switch and said second switch, for sensing the voltage present at said input and said output and for generating gating signals in response to the voltage sensed at said input and said output, wherein said controller changes from said first tap to said third tap by removing the gating signal from said first switch, generating said second and third gate signals to turn ON said second and third switches and thereafter generating said second gate signal to turn OFF said second switch.

2. The regulator of claim 1, wherein said first solid state switch comprises silicon controlled rectifiers.

3. The regulator of claim 1, wherein said first solid state switch comprises thyristors.

4. The regulator of claim 1, wherein said second solid state switch comprises a GTO.

5. The regulator of claim 1, wherein said second solid state switch comprises an IGBT.

6. The regulator of claim 1, wherein the output voltage resulting from said second tap is greater than the output voltage from said first and third tap.

7. The regulator of claim 1, wherein said second solid state switch is the only solid state switch in said regulator having the capability of being turned on and turned off in response to a gate signal.

8. A method of regulating the output of a voltage regulator, having a transformer with a secondary coil, said secondary coil having a plurality of taps, and having first and third solid state switches, connected between said output and a first one and a third one, of said taps, said first and third switches having the capability of being turned ON in response to first and third gate signals, said method comprising the steps of;

providing a second solid state switch, between said output and a second of said taps, said second switch having the capability of being turned ON and turned OFF in response to a second gate signal and wherein the output voltage resulting from said second tap is greater than said first and third taps;

sensing the voltage present at said input and said output; and

when desired to switch from said first tap to said third tap, removing said first gate signal, generating said second and third gate signals to turn ON said second and third switches and and thereafter generating a signal to turn OFF said second switch.