These motors are created for the application requirements of variable rate drive systems. You can expect both the following types of motors:
• Constant Torque: Motors particularly designed to handle continuous torque loads, such as conveyors, positive displacement pumps, cranes, etc.
• Variable Torque: Motors specifically designed to handle variable torque loads such as pumps and fans.
Due to fast switching and reflections in the cables, motors are at the mercy of more Variable Drive Motor voltage tension in the windings when fed by frequency converters than with sinusoidal supply voltage. The effect of these voltages can be an increase of up to 2.5 times the motor’s nominal voltage. This stresses the engine winding insulation and can cause it to break down, resulting in possible sparking. ABB recommends:
Between 500 V and up to 600 V, the motor needs to have reinforced winding insulation, or the drive will need to have a du/dt filter.
Above 600 V, the motor needs to have reinforced winding insulation and the drive must possess a du/dt filter.
If the cable duration between your drive and electric motor is higher than 150 meters and 
the voltage is between 600 and 690 V, the motor will need to have reinforced winding insulation.
A variable-frequency drive is something for controlling the rotational acceleration of an alternating electric current electric electric motor. It settings the frequency of the electrical energy supplied to the motor. A adjustable frequency drive can be a specific type of adjustable-velocity drive. Variable-frequency drives are also called adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, or inverter drives.
Automatic frequency control consist of an primary electric circuit converting the alternating electric current into a immediate current, then converting it back into an alternating current with the mandatory frequency. Internal energy loss in the automatic frequency control is rated ~3.5%
Variable-frequency drives are widely used on pumps and machine tool drives, compressors and in ventilations systems for large buildings. Variable-frequency motors on supporters save energy by enabling the volume of air flow moved to complement the system demand.
Reasons for employing automated frequency control can both be linked to the functionality of the application form and for saving energy. For instance, automatic frequency control is used in pump applications where the flow is matched either to quantity or pressure. The pump adjusts its revolutions to a given setpoint with a regulating loop. Adjusting the circulation or pressure to the real demand reduces power usage.
An AC motor acceleration control-also referred to as a variable frequency drive, adjustable frequency drive, variable rate drive, adjustable acceleration drive and AC inverter-is an electro-mechanical object that can be utilized to improve the output velocity of an AC motor by adjusting the insight frequency in to the motor.