EARTH LEAKAGE DETECTION CIRCUIT

• US 20100213905A1
• Filed: 09/01/2008
• Published: 08/26/2010
• Est. Priority Date: 10/30/2007
• Status: Active Grant

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Masuda, Tooru, Doumae, Hiroshi, Kagimura, Sumio
• Granted Patent: US 8,310,210 B2
• Time in Patent Office: Days
• US Class Current: 320/166
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 3/347 using summation current transformers

Abstract

A zero-phase current is outputted by detecting a ground-fault current with a zero-phase-sequence current transformer. A circuit having an open collector output operates when the voltage of the zero-phase current exceeds a positive side threshold value or it falls below a negative side threshold value to discharge a capacitor. When the inter-plate voltage of the capacitor falls below a threshold value voltage, a controlling means detects electric leakage to transmit that to a control unit of an air conditioner.

Claims

1. An electric leakage detection circuit comprising:

a zero-phase-sequence current transformer outputting a zero-phase current by detecting a ground-fault current;

a capacitor; and

a circuit operating when said zero-phase current exceeds a predetermined positive side threshold value or when said zero-phase current falls below a predetermined negative side threshold value, and controlling charge and discharge of said capacitor on the basis of said operation.

2. The electric leakage detection circuit according to claim 1, further comprising:

high potential points; and

a first resistor provided between said high potential points and said capacitor, wherein

said circuit employs an open collector output and an output terminal of said circuit is connected to a contact provided between said first resistor and said capacitor, and

one end of said capacitor is connected to said contact, and said capacitor is charged and discharged on the basis of output of said circuit.

3. The electric leakage detection circuit according to claim 2, wherein

said circuit includes an amplifier having an open collector output operating when said zero-phase current exceeds a predetermined positive side threshold value or when said zero-phase current falls below a predetermined negative side threshold value or wired OR circuits in which an amplifier having a push-pull output is applied;

and

second resistors connected between an output of said amplifier and said contact.

4. The electric leakage detection circuit according to claim 3, wherein

the other end of said capacitor is connected to a low potential point, and

a filter circuit is connected between said contact and said low potential point in parallel to said capacitor.