These motors are designed for the application form requirements of variable speed drive systems. You can expect 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 specifically designed to handle variable torque loads such as pumps and fans.
Due to fast switching and reflections in the cables, motors are subject to more voltage stress in the windings when fed by frequency converters than with sinusoidal supply voltage. The result of these voltages is definitely an increase of up to 2.5 times the motor’s nominal voltage. This stresses the engine winding insulation and will cause it to break down, resulting in feasible sparking. ABB recommends:
Between 500 V and up 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 will need reinforced winding insulation and the drive is required to 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 electric 
motor must have reinforced winding insulation.
A variable-frequency drive is a system for controlling the rotational quickness of an alternating current electric motor. It handles the frequency of the electrical power supplied to the electric motor. A variable frequency drive is definitely a specific type of adjustable-acceleration drive. Variable-frequency drives are also called adjustable-frequency drives (AFD), variable-swiftness drives (VSD), AC drives, or inverter drives.
Automatic frequency control consist of an primary electric circuit converting the alternating current into a direct current, after that converting it back to an alternating current with the mandatory frequency. Internal energy reduction in the automatic 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 followers save energy by allowing the volume of air moved to match the system demand.
Reasons for employing automatic frequency control can both be linked to the functionality of the application form and for conserving energy. For instance, automatic frequency control can be used in pump applications where in fact the flow is usually matched either to quantity or pressure. The pump adjusts its revolutions to confirmed setpoint with a regulating loop. Adjusting the flow or pressure to the real Variable Drive Motor demand reduces power usage.
An AC motor quickness control-also known as a adjustable frequency drive, adjustable frequency drive, variable quickness drive, adjustable quickness drive and AC inverter-is an electro-mechanical object that can be utilized to change the output rate of an AC engine by adjusting the input frequency in to the motor.