Weg Electronic Overload Relays

Weg electronic overload relays are an inexpensive solution to protecting expensive electric motors from burn-up due to overload conditions, phase-loss or current unbalances.  

Protected Conditions:

Overload  can occur when the motor is asked to do more work than it was designed for, or from mechanical failures in the machinery.  Attempting to run too much material too quickly through a machine is one common cause of failure.  Pump motors can also be overloaded by attempting to pump more water over a given amount of time than the motor was designed for.  Other mechanical faults can also cause overloading, including motor and machinery bearing failures.

Phase-Loss is a common cause of motor winding failures and occurs when one of the fuses in a three-phase circuit blows. Weg thermal overload relays detect phase-loss and shut down the motor by opening up the contactor.

Current Imbalance can occur when one there is a voltage drop or surge in one of the phases in incoming power.  The higher or lower voltage causes more or less current on one of the power leads to the motor, which can eventually burn up the windings. The Weg thermal overload relays sense current imbalance and shut down the motor.

Standard Features

  • Settable Class 10,20, or 30 Trip characteristics (read more below about Class trip ratings)
  • Selectable Auto/Man reset button (read more below)
  • Settable current overload range
  • Overload, phase-loss and current imbalance protection
  • Isolated 1 NO & 1NC contact
  • 2 and 3-pole versions available (single and three-phase)
  • Very low power draw, 87% more efficient than typical thermal overload relays

What is Trip Class?

Class 10, 20, and 30 ratings on overloads refer to how quickly the overload will respond to an overload event.  Similar to a fuse, the larger the overload, the more quickly the relay will trip.  The graphic below shows the response times vs overload for the 3 classes:

 thermal overload class trip graph

Auto / Manual Selectable Reset

The selector switch has two positions:

  • A  - Auto Reset: The relay will attempt to reset itself after the recovery time period.
  • Hand - Manual Reset: The relay will only reset after the button has been pressed and the recovery time period has elapsed