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The vast majority of circuit breaker failures are caused by improper operation of the breaker operating mechanism.

Circuit breakers are designed to trip at around 50% of rated nameplate DC voltage. This specification is extremely important when several circuit breakers are required to trip simultaneously, (i.e.: Bus Differential Faults) because the battery supply voltage drops due to the heavy current demand for these operations. Internal battery impedances can also limit the battery supply current.

Several factors can affect proper circuit breaker trip operations:

  • Improper lubrication
  • Old (sticky) lubrication
  • Shorted trip coil turns
  • Bad bearings
  • Improper adjustments on trip linkage
  • Bad (sticky) trip latch mechanism
  • High termination and wire resistances
  • Rust, etc.

The PS20 determines the minimum voltage and current (power) required to operate the circuit breaker. It is designed to plug into any 110VAC duplex outlet in the operating cabinet. The output is filtered with very low ripple and has adequate current to fully simulate the battery supply for tripping purposes.

To test an operating mechanism:

  1. With the breaker cleared, open the DC supply voltages at the circuit breaker operating cabinet.
  2. With the PS20 voltage at minimum, connect the output positive and negative leads to the load side of the supply switch.
  3. Set the PS20 for 50% of rated trip voltage.
  4. Momentarily jumper positive lead to the trip wire. If trip occurs, test was successful.
  5. Record this value for future reference.

Note: DC voltage should only be applied to the trip coil momentarily. Extended energization time could damage the trip coil.

Ideally the breaker should be tested upon installation for later comparison. Any future deviation of operating minimums is cause for concern and the mechanism should be checked for abnormalities. If the minimum to operate is near the 50% nameplate rating, the operating mechanism is functioning properly.

Other uses for the PS20

The "heart" of the substation is the battery bank and charging system. The PS20 can also be used as an emergency battery charging system due to the isolated 20 amp continuous duty rating. It will function in this capacity for short periods while repairs to the charging system are expedited.

The PS20 is also ideal for determining minimums for DC motors, relays and auxiliary equipment, radio and general test bench power supply uses.

PS20 Specifications
Output 0-140 VDC Filtered
0-20 Amp Continuous
Ripple Approx. 1% @ Full Load
Isolation DC-GRD 1500VRMS
Input 115VAC
Metering (Analog) 0-150 VDC, 0-20AMP DC
Downloadable Information

If you would like to download information about the PS-20, we have an informational booklet available for download in Adobe Acrobat format.

Adobe Acrobat Version

Don't have the right viewer for these files? The Acrobat viewer can be downloaded freely at the Adobe Web site.

Barrington Consultants, Inc.
2239 Valdes Court, Santa Rosa, CA 95403
Tel 707-527-8254 · Fax 707-542-9730 · Email ghb@barringtoninc.com

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