S91 is a protection device for electric motors that allows the detection of wrong phase sequence or lack of a phase, of the excess current consumption, no-load operation with the power factor measurement.

Equipped with rotary programming switches and a display of alarm signaling, the device is characterized by an input for PTC to protect the motor from overtemperature and enable input for starting the engine. S91 operates in 3 operation modes: single-phase or threephase, maximum current range 5 or 16 A, operation with or without PTC. Main applications are protection of single-phase or three-phase pumps for possible rotor stop and for overtemperature as well as device failure detection of mechanical transmission (e.g. belts or chains) with protection against transmission system lockdown.


  • Front diagnostics via LED and display.
  • Simplified settings and adjustments via trimmer and front selector.
  • Current measurement up to 16 A directly or by Current Transformer.
  • Maximum rated voltage 660 Vac (F-F).
  • Motor control input 195 ÷ 255 Vac.
  • SPDT Relay @ 250 Vac – 8 A.
  • Alarm, temperature, power factor, maximum current, minimum voltage or phase failure management.

Power supply

195 - 255 Vac (50-60Hz)

Power consumption

1,5 VA


250 g

Operating temp.

-20 to +65*C


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