Trip control circuit for circuit breaker

Patent metadata

Field	Value
Publication number	US-10483751-B2
Application number	US-201715495913-A
Country	US
Kind code	B2
Filing date	Apr 24, 2017
Priority date	Apr 28, 2016
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

The present invention provides a trip control circuit for a circuit breaker capable of breaking a circuit when a fault current occurs due to a DC current component, as well as an AC current. The trip control circuit comprises a current transformer that has a core allowing a circuit to pass through and a secondary coil for detecting a current flowing on the circuit and providing a current detection signal; an oscillation circuit section that configured to apply an electrical signal to the secondary coil to increase a slope of a hysteresis loop of the current transformer to allow the secondary coil to detect a DC current and an AC current; and a trip determining circuit section that configured to compare a current value indicated by the current detection signal with a predetermined reference current value.

First claim

What is claimed is:

1. A trip control circuit for a circuit breaker, the trip control circuit comprising:
a current transformer that has a ring-shaped core allowing a circuit to pass through and a secondary coil wound around the core for detecting a current flowing on the circuit and providing a current detection signal;
an oscillation circuit section that is configured to apply an electrical signal to the secondary coil of the current transformer to increase a slope of a hysteresis loop of the current transformer to allow the secondary coil to detect a DC current, as well as an AC current, flowing on the circuit; and
a trip determining circuit section that is configured to compare a current value indicated by the current detection signal having an AC component and a DC component output from the secondary coil of the current transformer with a predetermined reference current value, and output a trip control signal when the current value indicated by the current detection signal exceeds the reference current value, and
wherein the trip determining circuit section is configured to determine a current amount flowing on the circuit according to a change in time on the basis of the current detection signal, and determine a waveform and a frequency of the electrical signal to be supplied to the secondary coil through the oscillation circuit section.

2. The trip control circuit of claim 1 , further comprising a sensing resistor connected to the secondary coil of the current transformer that converts a current signal as a current detection signal provided by the secondary coil into a voltage signal, and outputs the converted voltage signal.

3. The trip control circuit of claim 1 , wherein the electrical signal applied by the oscillation circuit section is configured with a square wave signal.

4. The trip control circuit of claim 1 , wherein the electrical signal applied by the oscillation circuit section is configured with a sine wave signal having high frequency.

5. The trip control circuit of claim 1 , wherein the trip determining circuit section is configured to determine a signal of a waveform to be output by the oscillation circuit section on the basis of a relationship between a change in a magnetic field intensity generated in the secondary coil as time passed and a change in a magnetic flux density corresponding thereto.

6. The trip control circuit of claim 1 , further comprising a first display unit that displays a magnetic flux density and a magnetic field intensity of the secondary coil corresponding to a signal applied by the oscillation circuit section to the secondary coil.

7. The trip control circuit of claim 1 , further comprising a second display unit that is configured to display an information indicating that a DC component is detected, when the DC component flowing on the circuit passing through the core of the current transformer is detected.

8. The trip control circuit of claim 1 , wherein the trip determining circuit section is configured to receive a current detection signal from the secondary coil which has detected a current including at least one of a DC current component and an AC current component flowing on the circuit or a mixed current of the DC current and the AC current.

9. The trip control circuit of claim 1 , wherein the trip determining circuit section comprises a low pass filter circuit section that removes a high frequency signal that may be mixed in the current detection signal for a current induced to the secondary coil.

Assignees

• Lsis Co Ltd

Inventors

• Seon Jongkug

Classifications

• H01H83/144

  with differential transformer · CPC title

• H02H3/087

  for DC applications · CPC title

• G01R19/165

  Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values · CPC title

• H02H3/44

  responsive to the rate of change of electrical quantities · CPC title

• H01H83/226

  with differential transformer · CPC title