These motors are designed for the application requirements of variable velocity drive systems. We offer both the following types of motors:
• Constant Torque: Motors specifically designed to handle continuous torque loads, such as conveyors, positive displacement pumps, cranes, etc.
• Variable Torque: Motors particularly designed to handle adjustable torque loads such as pumps and fans.
Due to rapid switching and reflections in the cables, motors are at the mercy of more voltage stress 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 electric motor winding insulation and will cause it to breakdown, resulting in feasible 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 will need reinforced winding insulation and the drive must have a du/dt filter.
If the cable duration between the drive and electric motor is greater than 150 meters and the voltage is between 600 and 690 V, the engine will need to have reinforced winding insulation.
A variable-frequency drive is a system for controlling the rotational quickness of an Variable Drive Motor alternating current electric engine. It regulates the frequency of the 
electrical power supplied to the engine. A variable frequency drive is a specific type of adjustable-swiftness drive. Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-quickness drives (VSD), AC drives, or inverter drives.
Automatic frequency control consist of an primary electrical 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 ranked ~3.5%
Variable-frequency drives are widely used on pumps and machine device drives, compressors and in ventilations systems for huge buildings. Variable-frequency motors on supporters save energy by permitting the volume of atmosphere moved to complement the system demand.
Reasons for employing automated frequency control may both be related to the efficiency of the application and for conserving energy. For example, automatic frequency control is used in pump applications where in fact the flow is certainly matched either to volume or pressure. The pump adjusts its revolutions to confirmed setpoint with a regulating loop. Adjusting the flow or pressure to the actual demand reduces power intake.
An AC motor speed control-also referred to as a adjustable frequency drive, adjustable frequency drive, variable speed drive, adjustable velocity drive and AC inverter-is an electro-mechanical object that can be used to change the output rate of an AC electric motor by adjusting the input frequency in to the motor.