Self-learning relay turn-off control system and method

Patent metadata

Field	Value
Publication number	US-9754744-B2
Application number	US-201514835917-A
Country	US
Kind code	B2
Filing date	Aug 26, 2015
Priority date	Aug 19, 2015
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

An exemplary embodiment is disclosed of a relay turn-off control system for use with an alternating-current (AC) signal input. The system may include a relay, a relay current load sensor connected to the relay, and a rectifier circuit connected to the relay current load sensor and having an output. A microprocessor may be connected to the rectifier circuit output. The microprocessor may be configured to set a relay turn-off signal output time based on an empirically determined duration time for the relay to turn-off and further based on determining a zero-cross period via use of a modulo operation.

First claim

What is claimed is:

1. A relay turn-off control system for use with an alternating-current (AC) signal input, comprising:
a relay;
a relay current load sensor connected to the relay;
a rectifier circuit connected to the relay current load sensor and having an output;
a microprocessor connected to the rectifier circuit output; and
wherein the microprocessor is configured to:
a) define a plurality of successive time increments where each of the plurality of successive time increments combined are equal to a cycle time of the AC signal input;
b) output a first relay turn-off signal to the relay at a first of the plurality of successive time increments;
c) measure a duration time, after step b or f, for the rectifier circuit output to indicate that the relay has turned off;
d) perform a modulo operation of (duration time) mod (half the cycle time), wherein a remainder of the modulo operation is one of a non-zero value and a zero value;
e) store the remainder and an associated time increment in a memory coupled with the microprocessor;
f) output a next relay turn-off signal to the relay at a next of the plurality of successive time increments;
g) repeat steps c-f until the stored remainders of successive modulo operations transition from the non-zero value to the zero value or from the zero value to the non-zero value; and
h) set a relay turn-off signal output time at the associated time increment where the remainder of successive modulo operations transitioned from the non-zero value to the zero value or from the zero value to the non-zero value.

2. The control system of claim 1 , wherein the rectifier circuit output is synchronous with the AC signal input.

3. The control system of claim 1 , wherein the cycle time is divided into equal time increments.

4. The control system of claim 3 , wherein a number of the plurality of successive time increments is taken from a group consisting of 16, 32, and 64.

5. The control system of claim 1 , wherein the duration time is measured from a first rising edge to a last falling edge of the rectifier circuit output.

6. A relay turn-off control system for use with an alternating-current (AC) signal input, comprising:
a relay;
a relay current load sensor connected to the relay;
a rectifier circuit connected to the relay current load sensor and having an output;
a microprocessor connected to the rectifier circuit output; and
wherein the microprocessor is configured to set a relay turn-off signal output time based on an empirically determined duration time for the relay to turn-off and further based on determining a zero-cross period via use of a modulo operation;
wherein the zero-cross period is determined by configuring the microprocessor to:
a) define a plurality of successive time increments where each of the plurality of successive time increments combined are equal to a cycle time of the AC signal input;
b) perform a modulo operation of (duration time) mod (half the cycle time), wherein a remainder of the modulo operation is one of a non-zero value and a zero value;
c) store the remainder and an associated time increment in a memory coupled with the microprocessor;
d) output a next relay turn-off signal to the relay at a next of the plurality of successive time increments;
e) repeat steps b-d until the stored remainders of successive modulo operations transition from the non-zero value to the zero value or from the zero value to the non-zero value; and
f) set a relay turn-off signal output time at the associated time increment where the remainder of successive modulo operations transitioned from the non-zero value to the zero value or from the zero value to the non-zero value.

7. The control system of claim 6 , wherein the empirically determined duration time includes measuring, after the microprocessor outputs a relay turn-off signal to the relay, a time for the rectifier circuit output to indicate that the relay has turned off.

8. The control system of claim 7 , wherein the duration time is measured from a first rising edge to a last falling edge of the rectifier circuit output.

9. The control system of claim 6 , wherein the cycle time is divided into equal time increments.

10. The control system of claim 6 , wherein the rectifier circuit output is synchronous with the AC signal input.

11. A method performed by a microprocessor forming a part of a relay control system for use with an alternating-current (AC) signal input and where the relay control system includes a relay, a relay current load sensor connected to the relay, a rectifier circuit connected to the relay current load sensor and the microprocessor connected to a rectifier circuit output, comprising:
a) outputting a first relay turn-off signal to a relay at a first of a plurality of successive time increments where each of the plurality of successive time increments combined are equal to a cycle time of the AC signal input;
b) measuring a duration time, after step a or e, for the rectifier circuit output to indicate that the relay has turned off;
c) performing a modulo operation of (duration time) mod (half the cycle time), wherein a remainder of the modulo operation is one of a non-zero value and a zero value;
d) storing the remainder and an associated time increment in a memory coupled with the microprocessor;
e) outputting a next relay turn-off signal to the relay at a next of the plurality of successive time increments;
f) repeating steps b-e until the stored remainders of successive modulo operations transition from the non-zero value to the zero value or from the zero value to the non-zero value; and
g) setting a relay turn-off signal output time at the associated time increment where the remainder of successive modulo operations transitioned from the non-zero value to the zero value or from the zero value to the non-zero value.

Assignees

• Emerson Electric Co

Inventors

• Wan Lili
• Hu Daxing

Classifications

• H01H9/56

  for ensuring operation of the switch at a predetermined point in the AC cycle · CPC title

• H01H2047/009

  with self learning features, e.g. measuring the attracting current for a relay and memorising it · CPC title

• H01H2009/566

  with self learning, e.g. measured delay is used in later actuations · CPC title

• H01H47/002 Primary

  Monitoring or fail-safe circuits · CPC title