These motors are made for the application form requirements of variable speed drive systems. We offer both the following types of motors:
• Constant Torque: Motors specifically designed to handle continuous torque loads, such as for example conveyors, positive Variable Drive Motor displacement pumps, cranes, etc.
• Variable Torque: Motors particularly designed to handle adjustable torque loads such as pumps and fans.
Due to fast switching and reflections in the cables, motors are subject to more voltage tension in the windings when fed by frequency converters than with sinusoidal supply voltage. The effect of these voltages is definitely an increase as high 
as 2.5 times the motor’s nominal voltage. This stresses the motor winding insulation and may cause it to break down, resulting in feasible sparking. ABB recommends:
Between 500 V or more to 600 V, the motor will need 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 have got a du/dt filter.
If the cable duration between your drive and motor is greater than 150 meters and the voltage is between 600 and 690 V, the electric motor will need to have reinforced winding insulation.
A variable-frequency drive is a system for controlling the rotational quickness of an alternating electric current electric motor. It handles the frequency of the electrical energy supplied to the electric motor. 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-rate drives (VSD), AC drives, or inverter drives.
Automatic frequency control contain an primary electric circuit converting the alternating electric current into a direct current, then converting it back into an alternating current with the mandatory frequency. Internal energy reduction in the automated 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 fans save energy by enabling the volume of atmosphere moved to complement the system demand.
Reasons for employing automatic frequency control may both be linked to the efficiency of the application and for saving energy. For instance, automatic frequency control is utilized in pump applications where in fact the flow is definitely matched either to volume or pressure. The pump adjusts its revolutions to a given setpoint with a regulating loop. Adjusting the circulation or pressure to the actual demand reduces power intake.
An AC motor velocity control-also known 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 utilized to change the output acceleration of an AC electric motor by adjusting the input frequency in to the motor.