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Limiting the turn-to-turn insulation stress imposed on the device being protected

The motor surge protection bank (MSP) provides protection against insulation failure for motors, other rotating machines, and dry-type transformers. This yields assurance of continuous operation of the equipment, the electrical system and the manufacturing process.

The primary function of the MSP motor surge protection bank is to guard the winding insulation of the device being protected. Station class, and metal oxide lightning arresters act to limit the maximum voltage to the device, at a predetermined  magnitude. Specially designed surge capacitors, connected in parallel with the arresters, control the rate of rise of the resultant overvoltage. The combination of surge arresters and surge capacitors serve to limit the turn-to-turn insulation stress on the device being protected.


  • High voltage motors and generators
  • Dry-type transformers 
  • Motor control centers
  • Medium-voltage switchgear

Why Hitachi Energy?

  • High transient overvoltage withstand
  • Low operating losses
  • Long lifetime
  • All-film units with a non-PCB completely biodegradable dielectric fluid
  • Simplified external connections
  • Compact modular enclosure
  • Adaptable to customer needs

Brief performance data

Voltage range 1-24 kV
Enclosure NEMA 3R
Temperature range -50°C-60°C
Impregnant Non-PCB
Discharge time 5 minutes

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