Y, reduced voltage startMotor stator winding for delta connection, start with Y, close to the speed of the rated speed to the operation, the startup, reduce the stator winding of each phase to 58% power supply voltage, the starting current is directly at the start of 33%, the starting torque directly at the start of 33. A small startup current, start torque is small.The advantages of Y step-down start is not required to add boot device, a start switch or AC contactor control equipment can be achieved, the drawback is only used for delta connected motor, asynchronous motor can not load start.
Starting with buck transformerThe autotransformer start voltage, the starting current and starting torque of the motor and the end is proportional to the square of the lower, to obtain a large starting current to start the same situation. Such as starting voltage to 65% rated voltage, the starting current is full voltage starting current starting torque is 42%, full voltage starting torque 42%.The advantages of self coupling transformer step-down start is the direct manual control, automatic control can also be used for AC contactor, durable, low maintenance cost, suitable for all the no-load and light load start using asynchronous motor, is widely used in the production practice. The disadvantage is the manual operation to transformer box configuration more expensive (from I), automatic control box compensator to configure auto transformer, AC contactor start-up equipment and components.
Direct startThe advantages of direct start is required to start simple, less equipment, low cost. Current motor direct start is about 5 times the normal operation of the motor, often start, power supply line or transformer capacity should be greater than the motor capacity of more than 5 times; the motor is not frequent starting, power supply line or transformer capacity to the motor motor capacity should be more than 3 times. The requirements for small capacity motor is easy to be realized, so the vast majority of small capacity motor is started directly, without the need for a large amount of motor step-down start. It is a power supply line and transformer capacity is difficult to meet the motor direct start on the other hand, the strong impact of the grid and the motor starting current, affect the service life of the motor, the stable operation of the power grid so adverse, large capacity Motors and motors that do not start directly should be started by lowering voltage
