Single phase capacitor

Firstly let me describe about what is capacitor?This device is very common used in electronic and electric application.The main function is to stored and release electricity charge.

It charge and release depend on frequency ( Hz ) of our power supply.Normally around 50 until 60 times per second in alternating current system.

The construction of capacitor basically made from wound layers of metalized polypropylene (dielectric).The element is sealing in a plastic can with a suitable sealing material.

We can see a two metal plates insulated from each others.For oil filled type,it use a PCB`s as a coolant agent,but now almost capacitor is dry type.

Capacitor description

Single phase motor will not run properly if we wrong to sizing a rated of capacitor. Why sizing a rated of capacitor is so important?The reason is,when capacitor rated size too large,it can cause energy consumption rise. In other meanings,if rated sizing is too large or too small, the life span of the motor will be shorted due to overheated motor windings.

All motor manufacturers around the world always make a experiment and testing motor and capacitor combinations to get a best result and efficient.Normally a we used a range of  maximum of +10% tolerance in microfarad rating to replacement a start capacitors.

Voltage rating must always be the same or greater than original capacitor whether it is a start or run capacitor.If we not sure how to sizing the capacitor,please contact manufacturers to verify it to ensure suitable with your application.

For alternating current application,normally capacitor used for :-

  • Starting and running single phase induction motor
  • Power factor correction of fluorescent and discharge lamp
  • Single phase supply of 3 phase synchronous motor


  1. Sridhar S says

    In our area average voltage is 130 to 150 in single phase, we have 3hp submersible pump motor 41 stage and put
    Starting Capacitor is 50
    Running capacitor are 125
    Please give us suggestions for correct starting capacitor and running capacitor capacity
    Due to the power fluctuations water not coming properly

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