Average voltage detector for nonlinear waveforms

• US 3,898,551 A
• Filed: 05/02/1974
• Issued: 08/05/1975
• Est. Priority Date: 05/02/1974
• Status: Expired due to Term

• Current Assignee: Robert B. Webb
• Original Assignee: Robert B. Webb
• Inventors: Webb, Robert B.
• Primary Examiner(s): Goldberg, Gerald
• Application Number:
  US05/466,365
• Time in Patent Office: 460 Days
• Field of Search: 321/5,10 322/27,28,72,DIG.6
• US Class Current: 322/28
• CPC Class Codes: H02P 9/305 controlling voltage H02P9/302 takes precedence
• CPC Class Codes: Y10S 322/06 Ripple sensitive

Abstract

A voltage regulator for use with non-linear loads comprising a 3 to a higher phase section-wound transformer for converting a 3 phase generator waveform to the higher phase, a full-wave rectifier for rectifying the higher phase output, a smoothing filter for removing the high harmonics and noise, a differential amplifier for comparing this smoothed and rectified waveform to a voltage reference, and an amplifier for amplifying the difference signal and applying it as an error signal to control the voltagegenerated field.

Claims

1. A voltage regulator system for a voltage generator providing a 3-phase output comprising:

first means for converting said 3-phase output to a waveform of a higher phase;

rectifier means coupled to receive and rectify said higher-phase waveform;

filter means coupled to the output of said rectifier means with a high cutoff frequency for filtering out high frequencies and noise, said filter means having a minimal voltage discharge during its operation;

comparing means coupled to said filter means for providing an error signal representative of the difference between the filtered signal and a reference voltage; and

second means responsive to said error signal for controlling said voltage generator.

2. A voltage regulator as in claim 1, wherein said first means is a section-wound transformer, said rectifier means is a full-wave rectifier, and said second means includes a winding for affecting the field of said generator.

3. A voltage regulator as in claim 2 wherein said transformer means is a 3-to 6-phase transformer with a delta-connected primary and delta-and Y-connected secondaries.

4. A voltage regulator as in claim 3, wherein said full-wave rectifier means comprises two 3-phase diode bridges connected in series to effect a 6-phase fullwave rectification.

5. A voltage regulator as in claim 2, wherein said filter means comprises two inductors connected in series with respect to each other and with respect to said fullwave rectifier means;

and a capacitor connected in shunt across said rectifier means outputs and with one terminal connected at the point between said two inductors, the values of said inductors and capacitor being chosen so that said filter means operates in a resonant mode at the frequency of interest.

6. A voltage regulator as in claim 2, wherein said comparing means is a differential amplifier.

7. A voltage regulator as in claim 6, wherein said comparing means further comprises amplifying means for amplifying the difference signal from said differential amplifier.

8. A voltage regulator as in claim 7, wherein said amplifying means is a transistor with its base connected to the output from said differential amplifier.

9. A method for accurately regulating the three-phase A.C. voltage of a circuit under a nonlinear load comprising the steps of:

sampling said three-phase A.C. voltage;

converting said sampled voltage to a waveform with a higher phase;

rectifying said higher-phase waveform;

filtering said rectified waveform with a low pass filter with a high cutoff frequency so that high frequencies and noise are filtered out of said waveform, said filtered waveform remaining directly proportional to said input A.C. waveform, said filter being designed so that there is minimum voltage discharge;

comparing said filtered waveform with a reference waveform and providing an error signal representative of the difference between said filtered waveform and said reference waveform; and

controlling said three-phase A.C. voltage in said circuit in accordance with said error signal.

10. A method as defined by claim 9 wherein said converting step is performed by section-wound transformers.