Browse Prior Art Database

THREE PHASE MOTOR ANTI-REVERSAL CIRCUIT

IP.com Disclosure Number: IPCOM000026177D
Original Publication Date: 1990-Oct-31
Included in the Prior Art Database: 2004-Apr-05
Document File: 2 page(s) / 76K

Publishing Venue

Xerox Disclosure Journal

Abstract

To cause a three phase motor to be unidirectional, a device is required to monitor the phase relations of the source lines and switch any two of them if incorrect. Figure 1 shows a three phase motor anti-reversal circuit 10 with trigger circuit 12 triggering a comparator latch combination 14. By triggering comparator 14 on the positive zero crossing of one of the phases, for example phase B, the polarity of phases A and C can be positively determined. Since phase B is near zero, the other two phases will be at approximately 90% of their peak positive and negative values. If the incoming phases are of the correct polarity at that time, comparator 14 will latch and no further action is required. If they are of the wrong relative polarity, comparator 14 will latch and output a signal to power line reversing relay 16 and switch the B and C phases to the motor or system. This switching need only take place once at the time the circuit is applied to the line. Circuit 10 can be powered by the line it is monitoring and be small enough to be built into a motor, making it selectably unidirectional by the end user (by adding a switch) and not sensitive to power line phase.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 86% of the total text.

Page 1 of 2

XEROX DISCLOSURE JOURNAL

ec

8A

THREE PHASE MOTOR ANTI- Proposed Classification REVERSAL CIRCUIT U.S. C1.318/545 James E. Harmon Int. C1. HOlh 1/00

power I i ne reversing 0A or 8C rela ye

3 Phase Sine

0" 60 120 180 240 300 360"

PHASE ANGLE

f l6

4 06

BB

circuit

10 /

FIG. 1

XEROX DISCLOSURE JOURNAL Vol. 15 No. 5 September/October 1990 301

[This page contains 2 pictures or other non-text objects]

Page 2 of 2

THREE PHASE MOTOR ANTI-REVERSAL CIRCUIT(Cont'd)

302 XEROX DISCLOSURE JOURNAL Vol. 15 No. 5 September/October 1990

To cause a three phase motor to be unidirectional, a device is required to monitor the phase relations of the source lines and switch any two of them if incorrect. Figure 1 shows a three phase motor anti-reversal circuit 10 with trigger circuit 12 triggering a comparator latch combination 14. By triggering comparator 14 on the positive zero crossing of one of the phases, for example phase B, the polarity of phases A and C can be positively determined. Since phase B is near zero, the other two phases will be at approximately 90% of their peak positive and negative values. If the incoming phases are of the correct polarity at that time, comparator 14 will latch and no further action is required. If they are of the wrong relative polarity, comparator 14 will latch and output a signal to power line reversing relay 16 and switch the B and C phases to the motor or system. This switching need only take place once at the time the circuit is applied to the lin...