We Know That You Believe in Motor Protection!

But, are you protecting your motor from regenerative voltages too?
  • Check the specs on the units you are using now
  • Make sure they state "% unbalance"
  • Symcom's products do!
During phase loss, a motor can regenerate more than 92% of the supply voltage in the open phase. This phenomenon occurs because the disconnected winding acts as a generator. This regenerative voltage can fool “voltage averaging” and “phase shift detecting” voltage monitors into believing that a phase loss is not occurring. For proper protection, a voltage monitor MUST sense 6% to 8% unbalance; otherwise, phase loss may not be detected.

As with all SymCom 3-phase voltage monitors, our new 201-XXX-DPDT protects against regenerative voltages by detecting small voltage unbalances. The 201-XXX-DPDT family of products has a fixed 6% voltage unbalance trip point making them better than the NEC standard of 8%.

The 201-xxx-DPDT is used to prevent damage caused by incoming voltage problems, including regenerative voltages. It is a 11-pin octal base plug-in 3-phase voltage monitor that features two isolated Form C relay outputs and is ideal for use with two control circuits with different voltages.
  • 201-100-DPDT for 95-120VAC, 50/60Hz motors
  • 201-200-DPDT for 190-240VAC, 50/60Hz motors
The 201-xxx-SP-DPDT single-phase models are also available.
  • 201-100-SP-DPDT for 95-120VAC, 50/60Hz motors
  • 201-200-SP-DPDT for 190-240VAC, 50/60Hz motors
DPDT products allow one set of relay contacts to control/protect a motor, while the second set of contacts can be used for an alarm circuit operating on a different voltage. Typically the control contacts would switch 115VAC control circuit, while the alarm contacts would switch a 24VDC circuit monitored by a PLC or other low voltage equipment.


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