Arc detector for electric rod furnace

• US 4,376,243 A
• Filed: 01/26/1981
• Issued: 03/08/1983
• Est. Priority Date: 01/26/1981
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Koeller, William J., Renn, Charles F.
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US06/228,293
• Time in Patent Office: 771 Days
• Field of Search: 219/490, 219/492, 219/497, 219/507, 219/508, 219/509, 219/514, 219/518, 219/519, 219/502, 361/92, 361/235, 361/5, 13/12, 13/13, 340/146.34, 340/168 B, 340/650, 340/664, 373/102, 373/104
• US Class Current: 219/514
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/07 and with permanent disconnection after a predetermined number of reconnection cycles
• CPC Class Codes: H02H 3/0935 the timing being determined by numerical means

Abstract

A current shunt in the power supply to an electric furnace generates a signal voltage proportional to furnace current. A voltage rate comparator senses a high change rate of signal level corresponding to arcs occurring in the furnace and the comparator output pulse is fed to a preset counter. The counter is reset periodically. If a predetermined number of pulses are registered by the counter within a preset time interval, the counter output will de-energize an output relay which turns the power supply off and energizes a warning signal.

Claims

1. Apparatus for detecting repetitive arcing in an electric furnace supplied by an electrical direct current source wherein an electrical current surge accompanies each arc event comprising

detector means responsive to surges in the direct current flow for producing an arc pulse each time the current change exceeds a predetermined rate,

a counter preset for a given count and connected to the detector means to count each arc pulse for producing a counter signal when the counter reaches the said given count,

timer means for producing a regular series of reset pulses defining predetermined sample periods, the reset pulses being coupled to the counter to reset the counter at the occurrence of each reset pulse so that the counter is able to reach the given count only when the required number of arc pulses occurs within a single sample period, and

output circuitry for producing an output when the counter produces a counter signal.

2. Apparatus for detecting and stopping repetitive arcing in an electric rod furnace supplied by an electrical direct current source wherein an electrical current surge accompanies each arc event comprising

means sensing the direct current flow to the furnace and generating an electrical signal substantially proportional thereto,

detector means responsive to surges in the signal for producing an arc pulse each time the signal change exceeds a predetermined rate,

a counter preset for a given count and connected to the detector means to count each arc pulse for producing a counter signal when the counter reaches the said given count,

timer means for producing a regular series of reset pulses defining predetermined sample periods, the reset pulses being coupled to the counter to reset the counter at the occurrence of each reset pulse so that the counter is able to reach the given count only when the required number of arc pulses occurs within a single sample period, and

output circuitry coupled to the current source of turning off the current when the counter produces a counter signal.

3. Apparatus for detecting and stopping repetitive arcing in an electric rod furnace supplied by an electrical direct current source wherein an electrical current surge accompanies each arc event comprising

detector means responsive to surges in the direct current flow for producing an arc pulse each time the current change exceeds a predetermined rate,

a counter preset for a given count and connected to the detector means to count each arc pulse for producing a counter signal when the counter reaches the said given count,

timer means for producing a regular series of reset pulses defining predetermined sample periods, the reset pulses being coupled to the counter to reset the counter at the occurrence of each reset pulse so that the counter is able to reach the given count only when the required number of arc pulses occurs within a single sample period, and

output circuitry including a latch means for producing a continuous output for energizing a relay when the counter produces a counter signal,

the relay being coupled to the current source to turn off the current upon relay energization.