How to Select the Correct Contactor, Circuit Breaker, Thermal Relay for the Motor

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Motor power (KW) to current (A), this problem many partners are consulting this problem. We are here to arrange an estimate for your reference:

Under normal circumstances, we know the power of the motor, but do not know how to choose AC contactors and circuit breakers and thermal relays. 


So let's simply estimate to choose how much current products:


First of all, we need to know what occasion our motor is used in, whether the use frequency is high or low. 


If the use frequency is high, the circuit breaker and contactor we want to choose should have a larger current than the products with lower frequency. 


There are also different choices of domestic contactor and imported contactor. Here we take domestic products for example to make a choice. It should be added that the motor is less than 5KW under the condition of direct start, greater than 5KW is soft start; The voltage is estimated at 380V. The 220V voltage is explained later.


It is recommended to amplify the current by 20% to ensure the safe use of contactors for frequent starts or long lines. Similarly, the circuit breakers and thermal relays also amplify the current by 20%.


Note: The table below 5.5 KW (including 5.5 KW) is for direct start, above 5.5 KW is for soft start or vacuum start.


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