There are two ways to effectively reduce the voltage at the start, the first is supplying current at normal voltage, forcing the motor to connect in the network with the winding to a higher voltage, thus using the star-delta starting system. The second way is to supply current under voltage, by means of resistors, inductors or autotransformer.
All low voltage starting systems have drawbacks as the starting torque or torque reduces according to the square of the voltage reduction supplied to the motor. The electric motors of direct current, the speed must be regulated by the insertion of a rheostat in the field circuit, to provide adjustments in the flow.
The link between motors 1125-4-200-EA and a public power grid must follow specific requirements for this purpose, determined by standards. In most cases, it is necessary to remove a motor at full voltage in order to take full advantage of the starting torque. When starting the full voltage of an electric motor causes a voltage drop higher than the maximum permissible, it is important that a specific starting device with reduced voltage is used.