These motors are designed for the application requirements of variable swiftness drive systems. We offer both the following types of motors:
• Constant Torque: Motors specifically designed to handle constant torque loads, such as conveyors, positive displacement pumps, cranes, etc.
• Variable Torque: Motors particularly designed to handle variable torque loads such as pumps and fans.
Due to rapid switching and reflections in the cables, motors are at 
the mercy of more voltage tension in the windings when fed by frequency converters than with sinusoidal supply voltage. The result of these voltages can be an increase as high as 2.5 times the motor’s nominal voltage. This stresses the electric motor winding insulation and will cause it to break down, resulting in possible sparking. ABB recommends:
Between 500 V and up to 600 V, the motor will need reinforced winding insulation, or the drive must have a du/dt filter.
Above 600 V, the motor will need reinforced winding insulation and the drive is required to possess a du/dt filter.
If the cable length between the drive and 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 a system for controlling the rotational acceleration of an alternating electric current electric engine. It handles the frequency of the electrical power supplied to the engine. A adjustable frequency drive can be a specific kind of adjustable-velocity drive. Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-swiftness drives (VSD), AC drives, or inverter drives.
Automatic frequency control contain an primary electric circuit Variable Drive Motor converting the alternating electric current into a immediate current, then converting it back to an alternating current with the required frequency. Internal energy loss in the automated frequency control is ranked ~3.5%
Variable-frequency drives are trusted on pumps and machine tool drives, compressors and in ventilations systems for large buildings. Variable-frequency motors on followers save energy by permitting the volume of atmosphere moved to match the system demand.
Reasons for employing automatic frequency control may both be related to the features of the application and for saving energy. For instance, automatic frequency control is used in pump applications where the flow is certainly matched either to volume or pressure. The pump adjusts its revolutions to confirmed setpoint with a regulating loop. Adjusting the stream or pressure to the actual demand reduces power usage.
An AC motor acceleration control-also referred to as a variable frequency drive, adjustable frequency drive, variable speed drive, adjustable quickness drive and AC inverter-is an electro-mechanical object that can be used to improve the output acceleration of an AC motor by adjusting the insight frequency in to the motor.