Troubleshooting

James R. White, Shermco IndustriesColumns, Spring 2020 Columns, Tech Quiz

This issue of NETA World covers troubleshooting. A big part of that is being able to interpret a schematic, and some of the most difficult are those for circuit breakers (unless you work in the circuit breaker shop, I suppose). Give these questions a try. Here’s a big call-out to retired Instructor Craig Nelson, who got tired of my hand drawings and made these nice, legible ones.

1. What is the purpose of the Y coil in the generic schematic (Figure 1)?

  • Do we care?
  • It is part of the trip circuit of the circuit breaker.
  • It is the anti-pump coil to prevent the breaker from reclosing.
  • It prevents the motor from charging.

2. What does the 52a contact do? How does it close?

  • The 52a contact prevents or allows the trip coil from operating. It closes when the circuit breaker opens.
  • The 52a contact prevents or allows the trip coil from operating. It closes when the circuit breaker closes.
  • The 52a contact prevents or allows the motor from charging. It closes when the circuit breaker closes.
  • The 52a contact prevents or allows the motor from charging. It closes when the circuit breaker opens.

3. Conversely, what is the purpose of the 52b contact? How does it operate?

  • The 52b contact allows or prevents the closing coil from operating. It closes when the circuit breaker opens.
  • The 52b contact allows or prevents the closing coil from operating. It closes when the circuit breaker closes.
  • The 52b contact allows or prevents the trip coil from operating. It closes when the Y coil is opened.
  • The 52b contact allows or prevents the trip coil from operating. It closes when the Y coil is closed.

4. What causes the 52 contacts to open or close?

  • When a coil in the circuit is energized, either 52a or 52b operates.
  • The contacts are connected to the circuit breaker main operating mechanism.
  • It’s mostly an act of God around here.
  • It operates by switch action.

 

 

James (Jim) R. White, Vice President of Training Services, has worked for Shermco Industries Inc. since 2001. He is a NFPA Certified Electrical Safety Compliance Professional and a NETA Level 4 Senior Technician. Jim is NETA’s principal member on NFPA Technical Committee NFPA 70E®, Electrical Safety in the Workplace®, NETA’s principal representative on National Electrical Code® Code-Making Panel (CMP) 13, and represents NETA on ASTM International Technical Committee F18, Electrical Protective Equipment for Workers. Jim is Shermco Industries’ principal member on NFPA Technical Committee for NFPA 70B, Recommended Practice for Electrical Equipment Maintenance and represents AWEA on the ANSI/ISEA Standard 203 Secondary Single-Use Flame Resistant Protective Clothing for Use Over Primary Flame Resistant Protective Clothing. An IEEE Senior Member, Jim received the IEEE/IAS/PCIC Electrical Safety Excellence Award in 2011 and NETA’s Outstanding Achievement Award in 2013. Jim was Chairman of the IEEE Electrical Safety Workshop in 2008 and is currently Vice-Chair for the IEEE IAS/PCIC Safety Subcommittee.