Method for evaluating the temperature of an electro-magnetic contactor and contactor for implementation of said method

Patent metadata

Field	Value
Publication number	US-9506816-B2
Application number	US-201213686470-A
Country	US
Kind code	B2
Filing date	Nov 27, 2012
Priority date	Dec 2, 2011
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

A method for evaluating the temperature of a contactor comprising a processing unit designed to act on control means of the voltage applied to an actuating coil. Measuring means measure an electric current flowing in said at least one actuating coil. The method consists in:
sending a closing order consisting in applying a voltage to the terminals of the actuating coil enabling the electric current flowing in the coil to be modified up to a first reference value; sending a drop-out order consisting in fixing a voltage called drop-out voltage at the terminals of the actuating coil; measuring the electric current flowing in said actuating coil; performing acquisition of specific values on a signal of the electric current; analyzing specific values for evaluation of the operating temperature of the actuating coil.

First claim

The invention claimed is:

1. A method for evaluating the temperature of a contactor, which contactor comprises:
power contacts movable to and from open and closed positions, respectively,
at least one actuating coil,
control means of voltage applied to the actuating coil,
a processing unit designed to act on the control means of the voltage applied to the actuating coil, and
measuring means of electric current flowing in said at least one actuating coil;

said method, comprising:
sending a closing order from the processing unit which applies a voltage V 1 to terminals of the actuating coil enabling an electric current to flow in the coil up to a first reference value I1;
sending a drop-out order from the processing unit to the control means thereby fixing a drop-out voltage at the terminals of the actuating coil;

setting a reference value of one of (a) an electric current I2 flowing in the actuating coil, or (b) a time elapsed DT, alter a drop-out order is sent;
and if electric current (a) is the set reference value, then measuring the time elapsed DT for the electric current to reach said set reference value after a drop-out order is sent,
or if time elapsed (b) after a drop-out order is sent is the set reference value, then measuring the second electric current I2 flowing in the actuating coil at said set reference value of elapsed time;
the processing unit determining the operating temperature of the actuating coil-after a drop-out order has been sent by:

determining the value of the resistance Rcoil of the actuating coil from the first and second reference values of the electric current and the elapsed time, said resistance of the actuating coil being expressed in the equation:
( I 2+ U coil /( R coil +R eps ))/( I 1+ U coil /( R coil +R eps ))=exp(− DT×R coil /L coil )

wherein:
I1 is the first reference value of the electric current,
I2 is the second value of the electric current,
DT is the elapsed time,
U coil is equal to the coil voltage,
R eps is equal to the sum of the additional resistances present in the electronic circuit, and
L coil is the inductance of the coil;

and wherein, the temperature T bob of the actuating coil is expressed in the equation:
T bob =T init +( R bob /R init −1)/α,

wherein:
α is the thermal coefficient of the electric resistance, and
R init is equal to a resistance of the coil at an initial temperature T init ;

and voltage U coil applied to the coil by the control means is maintained in a range between voltage V 1 corresponding to the first reference value I1 of the electric current, and a voltage V 2 corresponding to the second value I2 of the electric current, which range correlates to a corresponding range of operating temperatures.

2. The method for evaluating according to claim 1 , wherein the second value I2 is lower than the first reference value I1.

3. The method for evaluating according to claim 1 , comprises measuring an elapsed time DT of the electric current flowing in the actuating coil to reach an electric current value I2, the electric current reference value being set and being lower than the first reference value.

4. The method for evaluating according to claim 1 , wherein measuring values of the electric current flowing in the actuating coil comprises plotting a decrease curve of the electric current in said coil between the first reference value and a second value.

5. The method for evaluating according to claim 4 , wherein determining the operating temperature of the actuating coil comprises comparing said decrease curve with a specific reference curve of operation of the contactor, evaluation of the temperature resistance of the contactor as a function of the positioning of said decrease curve with respect to said reference curve.

6. The method for evaluating according to claim 1 , wherein sending a drop-out order fixing a drop-out voltage at the terminals of the actuating coil is preceded by stabilization of the electric current.

7. The method for evaluating according to claim 6 , wherein the electric current is stabilized at the first reference value.

8. The method for evaluating according to claim 1 , wherein the drop-out voltage is fixed by a free wheel diode which places the actuating coil in “free wheel” mode throughout the entire period of elapsed time.

9. A contactor for implementation of the method for evaluating the temperature according claim 1 , comprising:
an electromagnetic actuator having a magnetic yoke and a ferromagnetic moving core;
an actuating coil;
control means connected to the actuating coil;
measuring means of the electric current in the actuating coil;
a processing unit having:
means for measuring an electric current flowing in the actuating coil, and measuring an elapsed time after a drop-out order from the control means to fix a drop-out voltage across the actuating coil;
means for analyzing said electric current and said elapsed time for evaluation of the operating temperature of the actuating coil.

10. The contactor according to claim 9 , comprising at least one free wheel diode connected in parallel with said at least one actuating coil and the measuring means.

11. The method for evaluating according to claim 1 wherein said method is commenced after an initial evaluation of an initial R coil and finding a corresponding acceptable temperature, and upon commencement of a closing phase initiated by sending another closing order causing application of another voltage V 1 which results in closure of the power contacts of the contactor.

12. The method for evaluating according to claim 11 , wherein finding a corresponding acceptable temperature comprises finding an initial T bob temperature corresponding to said initial R coil , and determining that said initial T bob is within said range of operating temperatures which correlate to the voltage range V 1 to V 2 .

13. Periodically repeating the method for evaluating according to claim 1 for periodically checking the temperature of the contactor.

Assignees

• Schneider Electric Ind Sas

Inventors

• Delbaere Stéphane
• Orban Rémy

Classifications

• H01H50/12

  Ventilating; Cooling; Heating (for operating electrothermal relays H01H61/013) · CPC title

• H01H2047/025

  with taking into account of the thermal influences, e.g. change in resistivity of the coil or being adapted to high temperatures · CPC title

• G01K7/00 Primary

  Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat (giving results other than momentary value of temperature G01K3/00) {; Power supply therefor, e.g. using thermoelectric elements} · CPC title

• H01H47/26 Primary

  having thermo-sensitive input · CPC title

• H01H47/002

  Monitoring or fail-safe circuits · CPC title