Study on Motor Soft Start

Abstract:
When electric motor is started by full voltage, 4~7 times of over current occurs. To achieve the purpose of reduce the over current, can using some methods such as resistance series connecting in power supply circuit, power supply by selftransformer, Y-Δ connection power supply, using frequency converter and etc. Compare with the others, using frequency converter is the best way to start the motor that makes the over current within acceptance range. This paper study on electric motor started by frequency converter to find the minimum start frequency that can make the over current under acceptable range and the maximum frequency that the maximum electromagnetic torque can make the motor rotated fastest. Simulation results by Matlab is shown in this paper to verify the correction of theoretical analysis.