Success with the sine filter
Spindle drives, high speed compressors, turbo blowers or micro turbines: sinusoidal filters are used in a wide variety of applications. Adapted to these applications a new electrical filter from KEB Automation is now available.
"The new Z2 output filters are designed for use on medium frequency motors from 200 to 1,600 Hertz", explains Dirk Erasmie, Head of Filter Development at KEB. "Such motors are typically used in high speed compressors, turbo blowers and micro turbines". Furthermore, there is a large number of spindle drives in the grinding, polishing and milling area.
For critical designs of medium frequency motors, it only makes sense to operate them on drive controllers if a Z2 sine filter is used. "Because the motor inductance of medium frequency motors is lower by approximately the factor mains frequency/motor frequency, direct operation of the motor on a drive controller often leads to overheating and thermal destruction of the motor," says Erasmie. Especially with permanent magnet motors, overheating of the rotor magnets can lead to demagnetization, i.e. also to motor failure.
If only one motor choke is required to reduce the ripple current, dv/dt, bearing currents or motor heating, a motor choke corresponding to the current is used. "If a sine filter is required, the motor choke is combined with one or more capacitor units," explains Dirk Erasmie. The sinusoidal filter converts the output pulse-width modulation (PWM) of the drive controller into a sinusoidal voltage. Therefore
- the switching frequency-related losses in the stator and rotor are eliminated,
- bearing currents avoided,
- and the service life of the motor windings is increased.
The components of the Z2 filters are especially designed for higher frequencies. They are based on the special core material as well as the HF litz wires of the windings developed by KEB. The result is a design with very low losses (η > 0.99).