Differential current protection circuit breaker

• US 4,860,146 A
• Filed: 12/22/1987
• Issued: 08/22/1989
• Est. Priority Date: 12/22/1986
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Pohl, Fritz, Harr, Dieter
• Primary Examiner(s): DEBOER, TODD
• Application Number:
  US07/136,830
• Time in Patent Office: 609 Days
• Field of Search: 361/54-57, 361/58, 361/88, 361/89, 361/91, 361/111, 361/110, 361/42, 361/44
• US Class Current: 361/42
• CPC Class Codes: H02H 1/043 to inrush currents H02H1/046 takes precedence; differential protection of transformers H02H7/045
• CPC Class Codes: H02H 3/332 with means responsive to dc component in the fault current
• CPC Class Codes: H02H 3/337 avoiding disconnection due to reactive fault currents

Abstract

A differential current protection circuit breaker that operates as a magnetic amplifier has a secondary winding connected in series to a complex, predominately capacitive measuring impedance and a square wave generator. An evaluating circuit is connected at a tap and is actuated along a tripping device and a switch latch of a switching contact device. The evaluation circuit is blocked by a sensor that responds to extraneous current surges or voltage surges during a predetermined response time. A blocking device in the tripping device responds to the signals from the sensor.

Claims

1. A differential current protection circuit breaker, comprising:

a magnetic amplifying circuit having a secondary winding;

means for producing a complex, predominantly capacitive measuring impedance connected to said secondary winding;

a square wave generator connected in series to said impedance producing means through said secondary winding;

a tap between said impedance means and said squarewave generator;

an evaluation circuit connected to said tap for generating a control signal;

a switch for disconnecting said magnetic amplifying circuit;

means for tripping said switch in response to said control signal from said evaluation circuit; and

means for blocking said evaluation circuit from generating said control signal during current or voltages surges.

2. A differential current protection circuit breaker comprising:

a magnetic amplifying circuit having a secondary winding;

means for producing a complex, predominantly capacitive measuring impedance connected to said secondary winding;

a square wave generator connected in series to said impedance producing means through said secondary winding;

a tap between said impedance means and said squarewave generator;

an evaluation circuit connected to said tap for generating a control signal;

a switch for disconnecting said magnetic amplifying circuit;

means for tripping said switch in response to said control signal from said evaluation circuit; and

means for blocking said evaluation circuit from generating said control signal during current or voltages surges,

said evaluation circuit having a first stage having a rectifier and an integrating member and a second stage having a threshold switch connected to said first stage; and

said blocking means further comprising a coupling switch connected to a reference potential between said tap and between said square wave generator and said impedance producing means.

3. A differential current protection circuit breaker as claimed in claim 2, wherein said coupling switch comprises an optical coupling element, and further comprising a connection between said secondary winding and said square wave generator, said optical element being controlled by a current flow caused by a voltage difference between said connection and ground.

4. A differential current protection circuit breaker as claimed in claim 3, wherein said optical coupling element is controlled by current flow caused by a voltage difference between said secondary winding and a damping resistor ahead of said impedance producing means said voltage difference being measured with respect to a reference potential.

5. A differential current protection circuit breaker as claimed in claim 4, wherein said coupling switch comprises a series connection of said optical coupling element, a full-wave rectifier, a voltage threshold detector, an R-C storage capacitor and current-limiting resistor, and a current or voltage limiter.

6. A differential current protection circuit breaker as claimed in claim 2, wherein said coupling switch has two control lines and said secondary winding is connected between said control lines.