Synchronized reapplication of power for driving an electric motor

Patent metadata

Field	Value
Publication number	US-2016134207-A1
Application number	US-201514832780-A
Country	US
Kind code	A1
Filing date	Aug 21, 2015
Priority date	Nov 6, 2014
Publication date	May 12, 2016
Grant date	—

Abstract

One embodiment describes a method that includes, when a motor is disconnected from a power source: starting, using a control circuitry, a counter at a first voltage zero-crossing by either a source voltage or a back electromotive force generated by the motor; stopping, using the control circuitry, the counter at a next subsequent second voltage zero-crossing by either the source voltage or the back electromotive force; monitoring, using the control circuitry, a trend in counter values; and instructing, using the control circuitry, one or more switching devices to reconnect the power source to the motor after a local minimum in the counter value trend such that the source voltage is leading the back electromotive force.

First claim

1 . A method comprising, when a motor is disconnected from a power source:
starting, using a control circuitry, a counter at a first voltage zero-crossing by either a source voltage or a back electromotive force generated by the motor; stopping, using the control circuitry, the counter at a next subsequent second voltage zero-crossing by either the source voltage or the back electromotive force; monitoring, using the control circuitry, a trend in counter values; and instructing, using the control circuitry, one or more switching devices to reconnect the power source to the motor after a local minimum in the counter value trend such that the source voltage is leading the back electromotive force.

2 . The method of claim 1 , wherein stopping the counter comprises storing value of the counter in memory and resetting the counter,
wherein monitoring the trend in counter values comprises retrieving the counter value stored in memory.

3 . The method of claim 1 , comprising:
starting, using the control circuitry, the counter at a third voltage zero-crossing by either the source voltage or the back electromotive force; and stopping, using the control circuitry, the counter at a next subsequent fourth voltage zero-crossing by either the source voltage or the back electromotive force.

4 . The method of claim 1 , wherein instructing the one or more switching devices to reconnect the power source comprises instructing the one or more switching devices to reconnect the power source when the counter value trend is increasing.

5 . The method of claim 1 , wherein instructing the one or more switching devices to reconnect the power source comprises:
determining a counter value at the local minimum; and reconnecting the power source only if the counter value at the local minimum is less than a threshold value.

6 . The method of claim 1 , wherein the first voltage zero-crossing is a source voltage zero-crossing and the second voltage zero-crossing is a back electromotive force zero-crossing.

7 . The method of claim 1 , wherein the first voltage zero-crossing and the second voltage zero-crossing are source voltage zero-crossings.

8 . The method of claim 1 , wherein the first voltage zero-crossing is a back electromotive force zero-crossing and the second voltage zero-crossing is a source voltage zero-crossing.

9 . The method of claim 1 , wherein the back electromotive force is generated by momentum of the motor that causes the motor to rotate.

10 . The method of claim 1 , wherein frequency of the back electromotive force is decreasing and frequency of the source voltage is relatively constant.

11 . The method of claim 1 , comprising predicting, using the control circuitry, when the local minimum will occur based on type of load the motor is actuating.

12 . The method of claim 1 , comprising determining, using the control circuitry, type of load the motor is actuating based at least in part on when the local minimum occurs.

13 . A wye-delta motor starter, comprising:
one or more wye switching devices configured to selectively connect a source voltage to motor windings in a motor coupled to the motor starter in a wye configuration; and one or more delta switching devices configured to selectively connect the source voltage to the motor windings in a delta configuration; and a control circuitry configured to:
instruct the one or more wye switching devices to disconnect the source voltage from the motor windings;
start a counter at a first voltage zero-crossing by either the source voltage or a back electromotive force generated by the motor;
stop the counter at a next subsequent second voltage zero-crossing by either the source voltage or the back electromotive force; and
instruct the one or more delta switching devices to connect the source voltage to the motor windings when the source voltage is leading the back electromotive force based at least in part on a trend of counter values.

14 . The system of claim 13 , wherein the control circuitry is configured to instruct the one or more delta switching devices to connect the source voltage to the motor windings after a local minimum in the trend of counter values.

15 . The system of claim 13 , wherein the control circuitry is configured to instruct the one or more delta switching devices to connect the source voltage to the motor windings when the trend of counter values is increasing.

16 . The system of claim 13 , wherein the control circuitry is configured to:
start the counter at a third voltage zero-crossing by either the source voltage or the back electromotive force; and stop the counter at a next subsequent fourth voltage zero-crossing by either the source voltage or the back electromotive force, wherein the trend of counter values comprises a counter value at the second voltage zero-crossing and a counter value at the fourth voltage zero-crossing.

17 . A tangible, non-transitory, computer readable medium storing instructions executable by a processor in a control circuitry, wherein the instruction comprise instructions to, when a motor is disconnected from a power source:
monitor, using the control circuitry, characteristics of source voltage output by the power source; monitor, using the control circuitry, characteristics of back electromotive force output by the motor; monitor, using the control circuitry, a trend in differential between subsequent voltage zero-crossings by the source voltage or the back electromotive force; and determine, using the control circuitry, when to reenergize the motor based in the trend in differential between subsequent voltage zero-crossings such that the source voltage is leading the back electromotive force.

18 . The computer readable medium of claim 17 , wherein the instructions to monitor the trend in differential between subsequent zero-crossings comprise instructions to:
start a counter at a first voltage zero-crossing by either the source voltage or the back electromotive force; stop the counter at a next subsequent second voltage zero-crossing by either the source voltage or the back electromotive force, wherein the trend in differential between subsequent zero-crossings comprises a trend in counter values.

19 . The computer readable medium of claim 17 , wherein the instructions comprise instructions to predict when the source voltage is leading the back electromotive force based at least in part on type of load the motor is actuating.

20 . The computer readable medium of claim 19 , wherein the instructions to predict when the source voltage is leading comprises instructions to determine a frequency trend associated with the type of the load.

21 . The computer readable medium of claim 17 , comprising instructions to instruct one or more switching devices to close, thereby reenergizing the motor.

Assignees

• Rockwell Automation Tech Inc

Inventors

• Bock Christopher H
• Wieloch Christopher J
• Kinsella James J
• Dziekonski Stefan T

Classifications

• H01H50/002

  particular to three-phase electromagnetic relays (synchronous switching H01H9/563) · CPC title

• H02P1/26

  for starting an individual polyphase induction motor · CPC title

• H01H50/38

  Part of main magnetic circuit shaped to suppress arcing between the contacts of the relay · CPC title

• H01H47/26

  having thermo-sensitive input · CPC title

• H01H47/02

  for modifying the operation of the relay · CPC title