Gantry crane application phase AC motor

      hoist gantry crane  is applied in three-phase AC motors, asynchronous motors are induction effect.
     Rat Lung motor applies only to the power of very small spaces (such as small electric crane), in other cases, are using volume linear motors. Power is small, its rotor roll into two phases, medium power or high-power, then rolled into a three-phase.
     Three-phase AC motor stator winding directly connected to the power supply (no resistance), the rotor coil end connected to the three slip rings in each slip ring plus an adjustable resistor, these three resistors with a control can also be added at the same time can be removed. If you wish to change the rotational direction of the motor,overhead gantry crane the stator coils may be three sets of connectors to each other in two interchangeable.
     Over waves per second 50HZ, the motor nominal number of revolutions have 1500,1000,750 and 600.
     Three-phase AC induction motor, the idling also reached the nominal number of revolutions, even inserted in the rotor circuit resistance versa. If the motor with a load, the added resistor, it only reduces the number of revolutions. In the rotor coil shorted and connected as load equal to the full load torque, its rotation about only 5%, it can actually be regarded as constant - and DC shunt motor the same.
     If the three-phase AC motor driven by a load, a generator is used, then the number of revolutions exceeds synchronous number of revolutions of the rotor and the larger the resistance in the circuit, the higher is the number of revolutions.
     Three-phase AC motor maximum torque value, which we call overturning moment. If the motor load exceeds this value, then stops. And when the load is removed, but also automatic operation. In contrast, synchronous motor can not continue to rotate, to be re-start, it is not suitable for steel crane  applications.
     Overturning torque induction motor, with the time rate at 25% ED is approximately equal to 2.5-2.8 times the nominal torque. At 15% ED is small, when the 40% ED is greater.