Method for testing a latching magnet of a switch and test device for the latching magnet

Patent metadata

Field	Value
Publication number	US-9726727-B2
Application number	US-201514612333-A
Country	US
Kind code	B2
Filing date	Feb 3, 2015
Priority date	Apr 3, 2014
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A method is disclosed for testing a latching magnet of a switch including a switching contact, formed from contact elements mechanically separated from one another for opening the switching contact; an electronic trip unit, to monitor current flowing via the contact elements and to perform a test for a current-dependent trip condition; an electrical energy store, forming a circuit with the winding of the latching magnet, the circuit being closed for a first closing time when the trip condition of the trip unit is met; and an actuator, actuable by closing off the circuit and configured to separate the contact elements. For test purposes, the circuit is closed for a second closing time, which is so short that separation of the contact elements by the actuator does not take place. A test is then performed to ascertain whether there is a current flowing via the winding of the latching magnet.

First claim

What is claimed is:

1. A method for testing an electromagnetic latching magnet of a switch including a switching contact, formed from contact elements mechanically separated from one another to open the switching contact, the latching magnet including a permanent magnet, around which a winding is wound, the winding being tested for wire breakage, an electronic trip unit to monitor current flowing via the contact elements and to perform a test that a current-dependent trip condition is met, an electrical energy store, in the form of a capacitor, forming a circuit with the winding of the latching magnet, the circuit being closed for a first closing time when the trip condition of the trip unit is met, and an actuator, actuable by closing off the circuit and configured to separate the contact elements, the method comprising:
closing the circuit for a second closing time for test purposes by closing a transistor switch, the second closing time being so short that no separation of the contact elements by the actuator takes place, wherein when the transistor switch is closed, the capacitor, the winding of the latching magnet and a current sensor form a closed circuit and the capacitor is in a discharge mode; and
performing a test during the second closing time to ascertain whether a current is flowing via the winding of the latching magnet, wherein the flow of the corresponding current is detected by the current sensor, and wherein the current sensor is a diode, through which the corresponding current is arranged to flow, the method further comprising detecting whether there is a corresponding voltage drop across the diode.

2. The method of claim 1 , wherein a presence of the voltage drop is detected by use of a comparator.

3. The method of claim 2 , further comprising:
outputting, via the comparator, a signal when there is no corresponding voltage drop.

4. A test device for a latching magnet of a switch, the switch including a switching contact, formed from contact elements separated mechanically from one another when the switching contact is open and resting against one another when the switching contact is closed, an electronic trip unit to monitor current flowing via the contact elements and to perform a test to ascertain whether a current-dependent trip condition is met, a capacitor as an electrical energy store, forming, with a winding of a latching magnet, a circuit which is closed by the trip unit when the trip condition is met, wherein the latching magnet includes a permanent magnet, around which a winding is wound, the winding being tested for wire breakage, and an actuator, whose actuation is configured to be performed by closing of the circuit for a first closing time, and configured to separate the contact elements after the actuation, the test device comprising:
a current sensor to detect the current flow, the current sensor including a diode for detecting the current flow, wherein the test device is configured to close the circuit for test purposes for a second closing time by closing a transistor switch, the second closing time being so short that no separation of the contact elements by the actuator takes place, the capacitor, the winding of the latching magnet and the current sensor form a closed circuit when the transistor switch is closed, the capacitor being in a discharge mode, and to test, during the second closing time, whether there is a current flowing via the winding of the latching magnet by detecting a voltage drop across the diode.

5. The test device of claim 4 , further comprising:
a comparator, to detect the voltage drop.

6. The test device of claim 5 , wherein the comparator is configured to output a signal when there is no corresponding voltage drop.

Assignees

• Siemens Ag

Inventors

• Fischer Andreas
• Widmann Stefan

Classifications

• G01R31/3278

  of relays, solenoids or reed switches (measuring contact resistance G01R27/205; high voltage magnetic switches G01R31/3271, G01R31/333; testing electric windings G01R31/72; monitoring of fail safe circuits H01H47/002) · CPC title

• H01H50/32

  Latching movable parts mechanically · CPC title

• H01H51/01 Primary

  Relays in which the armature is maintained in one position by a permanent magnet and freed by energisation of a coil producing an opposing magnetic field {(H01H51/02 - H01H51/26 take precedence)} · CPC title

• H01H47/002

  Monitoring or fail-safe circuits · CPC title

• G01R31/333 Primary

  Testing of the switching capacity of high-voltage circuit-breakers {; Testing of breaking capacity or related variables, e.g. post arc current or transient recovery voltage} · CPC title