System and method for detecting loss of input phase by sensing before power rectifier

Patent metadata

Field	Value
Publication number	US-10644639-B2
Application number	US-201715665681-A
Country	US
Kind code	B2
Filing date	Aug 1, 2017
Priority date	Jul 9, 2014
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

A system for detecting a decrease in or loss of an input phase to a motor. A power rectifier rectifies and combines three input voltages to produce an output voltage to power the motor. A PFC circuit manages the power flowing to the motor. A sensing circuit located between the power rectifier and the PFC senses a voltage level of the power rectifier's output voltage. Alternatively, a sensing rectifier is connected before the power rectifier, and the sensing circuit senses the voltage level of the sensing rectifier's output voltage. A microprocessor compares the sensed voltage level to a threshold voltage level which is indicative of the decrease in or loss of one of the three input voltages, and if the former drops below the latter, then the microprocessor sends a signal to either shut off the motor or cause the PFC circuit to reduce the power flowing to the motor.

First claim

Having thus described one or more embodiments of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following:

1. A motor control system for an electric motor, the motor control system comprising:
a power rectifier configured to receive, rectify, and combine a plurality of spaced-apart sinusoidal input voltage phases to produce a first output voltage signal to power the electric motor;
a particular power factor correction circuit electrically connected to the power rectifier so as to receive the first output voltage signal from the power rectifier and configured to manage power flowing to the motor;
a sensing rectifier electrically connected in parallel with the power rectifier and configured to independently receive, rectify, and combine the same plurality of spaced-apart sinusoidal input voltage phases to produce a second output voltage signal;
a sensing circuit electrically connected to the sensing rectifier and configured to sense a voltage level of the second output voltage signal; and
a processor electrically connected between the sensing circuit and the particular power factor correction circuit, and configured to receive the sensed voltage level from the sensing circuit, compare the sensed voltage level to a predetermined threshold voltage level, which corresponds to a decrease in one of the plurality of spaced-apart sinusoidal input voltage phases, and if the sensed voltage level is below the predetermined threshold voltage level, send a signal to the particular power factor correction circuit to limit an output power to the electric motor, without shutting off the electric motor, based on a remaining one or more of the plurality of spaced-apart sinusoidal input voltage phases.

2. The motor control system as set forth in claim 1 , wherein the electric motor is a multiple-phase permanent magnet motor.

3. The motor control system as set forth in claim 1 , wherein the particular power factor correction circuit and the sensing circuit each use approximately the same reference voltage.

4. The motor control system as set forth in claim 1 , wherein the predetermined threshold voltage level corresponds to a loss of one of the plurality of spaced-apart sinusoidal input voltage signals.

5. The motor control system as set forth in claim 1 , wherein the predetermined threshold voltage level is adjustable.

6. A motor control system for an electric motor, the motor control system comprising:
a power rectifier configured to receive, rectify, and combine three spaced-apart sinusoidal input voltage phases to produce a first output voltage signal to power the electric motor;
a particular power factor correction circuit electrically connected to the power rectifier so as to receive the first output voltage signal from the power rectifier and configured to manage power flowing to the motor;
a sensing rectifier electrically connected in parallel with the power rectifier and configured to independently receive, rectify, and combine the same three spaced-apart sinusoidal input voltage phases to produce a second output voltage signal;
a sensing circuit electrically connected to the sensing rectifier and configured to sense a voltage level of the second output voltage signal; and
a microprocessor electrically connected between the sensing circuit and the particular power factor correction circuit, and configured to receive the sensed voltage level from the sensing circuit, compare the sensed voltage level to a predetermined threshold voltage level, which corresponds to a loss of one of the three spaced-apart sinusoidal input voltage phases, and if the sensed voltage level is below the predetermined threshold voltage level, limiting an input current and power on a remaining one or more of the plurality of spaced-apart sinusoidal input voltage phases by sending a signal to the particular power factor correction circuit to limit an output power to the electric motor, without shutting off the electric motor, based on the remaining one or more of the plurality of spaced-apart sinusoidal input voltage phases, and continuing to run the electric motor at the output power without shutting off the electric motor.

7. The motor control system as set forth in claim 6 , wherein the electric motor is a three-phase permanent magnet motor.

8. The motor control system as set forth in claim 6 , wherein the particular power factor correction circuit and the sensing circuit each use approximately the same reference voltage.

9. The motor control system as set forth in claim 6 , wherein the predetermined threshold voltage level is adjustable.

10. A method of controlling an electric motor, the method comprising:
(1) receiving, rectifying, and combining a plurality of spaced-apart sinusoidal input voltage signals using a power rectifier, and producing a first output voltage signal to power the electric motor;
(2) managing a power flowing to the electric motor using a particular power factor correction circuit electrically connected to the power rectifier so as to receive the first output voltage signal from the power rectifier;
(3) receiving, rectifying, and combining the same plurality of spaced-apart sinusoidal input voltage signals and producing a second output voltage signal using a sensing rectifier electrically connected in parallel with the power rectifier;
(4) sensing a voltage level of the second output voltage signal using a sensor;
(5) comparing the sensed voltage level of the second output voltage signal to a predetermined threshold voltage level using a microprocessor, wherein the predetermined threshold voltage level corresponds to at least a decrease in one of the plurality of spaced-apart sinusoidal input voltage signals;
(6) repeating step (5) a predetermined number of times during a predetermined period of time; and
(7) if the sensed voltage level is below the predetermined threshold voltage level for at least the predetermined number of times during the predetermined period of time, sending a signal from the microprocessor to at least limit the power flowing to the electric motor, without shutting off the electric motor, based on a remaining one or more of the plurality of spaced-apart sinusoidal input voltage phases.

11. The method as set forth in claim 10 , wherein the electric motor is a three-phase permanent magnet motor.

12. The method as set forth in claim 10 , wherein the particular power factor correction circuit and the sensing circuit each use approximately the same reference voltage.

13. The method as set forth in claim 10 , wherein the predetermined threshold voltage level corresponds to a loss of one of the plurality of spaced-apart sinusoidal input voltage signals.

14. The method as set forth in claim 10 , wherein the predetermined threshold voltage level is adjustable.

Assignees

• Nidec Motor Corp

Inventors

• Skinner James L
• Shahi Prakash B

Classifications

• H02P29/0243 Primary

  the fault being a broken phase · CPC title

• H02P23/26

  Power factor control [PFC] · CPC title