How large AC contactor and thermal relay should be used for the motor of 3KW? There are steps to calculate better.
3KW motor rated current is about 6A. The bigger contactor can prolong the service life of CJX20-1210 (12A) 8-10A air thermal relay's role is to protect the motor so do not benefit too much 7-8A can protect the motor when a fault occurs.
1, rated current = power *2, or 6A2, the selection of AC contactor, the current domestic > = rated current, usually for a minimum of 9A. The reason is why recommend you go with CJX1 0922 or CJX2 0911 9A.3 、 thermal relay is usually a current range, rated current included in the range, preferably near the middle, which is ideal.Selection of domestic products, circuit breakers, contactors and other appropriate amplification, because the quality is not reassuring.
1, Y-100L-4 type 3KW motor rated current is 6.4A, can also be obtained by formula: (power factor cos Phi about 0.7)I = P/ (root 3 * U * cos (3000/) = 1.732 x 380 x 0.7) = 6.5 (A)2 "AC contactor selection: general and motor current is available, but in actual use, the contact is easy to burn, choose more than the motor current double the more durable, should choose CJX2-1210 (12A).".3 "thermal relay setting current: choose regulating current range of 5 ~ 9A thermal relay, the setting current is 1.1 times the rated current of the motor (7A).
