How Single Phase Preventer Work and its Features

In the complex world of electrical systems, maintaining smooth operation is critical. One unsung hero in this realm is the Single Phase Preventer, a little but powerful gadget that performs an important role in protecting your electrical equipment. In this blog, we'll delve into the world of single-phase preventers, distilling down complex terminology into simple, accessible English.

What is a single-phase Preventer?


The Selfguard Single Phase Preventer (Auto Switch) provides complete safety up to the motor terminals against single phasing and unbalanced voltage circumstances. They trip the motor starter if the voltage exceeds the predetermined level and prevent the motor from starting under unfavourable supply conditions.


How Does It Work?


If all three phases are completed in the correct order, a Green Indicator will illuminate after a predetermined time, and the Single Phase Preventer will begin operation. If the phases are not in the proper order, the Red Indicator will begin blinking. If one of the three phases is missing, the Red Indicator will illuminate.




  • Microprocessor technology 
  • Detects reverse phase and voltage faults 
  • Automatically starts the motor 
  • Prevents motor from running in two phases 
  • Protects against unbalanced voltage conditions 
  • Prevents reverse running



In the magnificent symphony of electricity, the Single Phase Preventer emerges as a silent conductor, creating harmony between phases. Understanding its job as the protector of your electrical appliances allows you to comprehend the critical purpose it plays in maintaining the longevity and dependability of your precious equipment. Selfguard also deals in auto phase sequence corrector, automatic phase changer etc.


Read more about the Automatic Changeover Switch Vs Three Phase Automatic Transfer Switch.