Limitations of Starting Current

It is worth mentioning that the direct connection of the motors to a public electricity network must strictly follow the specific prescriptions for this purpose, pre-established by norm. It is necessary to start an engine at the exact instant of full voltage so that maximum torque can be used. When starting the full voltage of an electric motor causes a voltage drop greater than the maximum acceptable, a starting device with reduced voltage must be used, always being careful to check if the torque is enough to drive load.

It can be concluded that there are two ways to carry out voltage reduction at startup, the first of which consists of supplying the current to the normal voltage, thereby causing the motor to be temporarily connected to the grid, with the winding for a using the star-triangle starter system. The second method is to provide less than normal voltage current through resistors, inductors or autotransformer. All reduced voltage starting systems have, as opposed to the benefit of current reduction, the disadvantage that the starting torque or torque will be reduced in proportion to the square of the voltage reduction supplied to the motor.