These motors are made for the application form requirements of variable swiftness drive systems. You can expect both the following types of motors:
• Constant Torque: Motors specifically designed to handle constant torque loads, such as for example conveyors, positive displacement pumps, cranes, etc.
• Variable Torque: Motors specifically designed to handle adjustable torque loads such as for example 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 as high as 2.5 times the motor’s nominal voltage. This stresses the motor 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 will need reinforced winding insulation, or the drive must have a du/dt filter.
Above 600 V, the motor needs to have reinforced winding insulation and the drive is required to possess a du/dt filter.
If the cable size between your drive and 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 speed of an alternating electric current electric electric motor. It handles the frequency of the electrical energy supplied to the electric motor. A adjustable frequency drive is definitely a specific kind of adjustable-velocity drive. Variable-frequency Variable Drive Motor 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 current into a direct current, after that converting it back to an alternating electric current with the required frequency. Internal energy loss in the automatic frequency control is rated ~3.5%
Variable-frequency drives are widely used on pumps and machine device drives, compressors and in ventilations systems for large buildings. Variable-frequency motors on fans save energy by permitting the volume of air moved to match the system demand.
Reasons for employing automatic frequency control can both be related to the functionality of the application form and for saving energy. For instance, automatic frequency control is utilized in pump applications where the flow is matched either to volume or pressure. The pump adjusts its revolutions to a given setpoint via a regulating loop. Adjusting the circulation or pressure to the real demand reduces power consumption.
An AC motor velocity control-also known as a variable frequency drive, adjustable frequency drive, variable acceleration drive, adjustable swiftness drive and AC inverter-is an electro-mechanical object that can be utilized to change the output quickness of an AC engine by adjusting the insight frequency into the motor.