Operation with frequency converters

When using frequency converters, it is important to ensure that these have a high-quality sinus-filter (sine-wave filter) connected at the output. With reference to the European standard for rotating electrical machines, DIN IEC / TS 60034-17, the increased stress on the motor winding system by voltage spikes and the risk of bearing currents due to capacitive coupled voltage, must be prevented by a suitable (allpolar) sinus-filter.

Standard frequency converters without sinus-filters have a block-shaped or pulse-width-modulated (PWM) output voltage. The standard (DIN IEC / TS 60034-17) describes the increased stress of the motor winding system by voltage spikes (up to a dU / dt of 5000 KV / s), which can lead to the premature failure of the motors.The performance of electronic components has In recent years. This applies in particular to the IGBT modules (transistors) used in frequency converters. These electronic switches are necessary for generating the PWM voltage of the frequency converter. The high-frequency voltage pulses of the frequency converter are similar to a wave on the motor cable. These voltage pulses are reflected in the region of the motor. Similar to the double effect, overvoltages are created by the addition of the trailing wave, which can damage the motor in the winding. In the case of feed lines over 0.5 m, the effects mentioned can even intensify very quickly so that the motors are delivered even stronger pulse width modulated voltage spikes .


Although we already use the insulation class H in our motors, the ventilator-motor can be overloaded due to the thin winding. This applies, however, to all smaller motors which are operated with frequency converters without sinus-filters.

 For this reason, when using a frequency converter, ensure that an (all-pole) sinus-filter is installed at the output of the frequency converter. This might be already integrated at some frequency converters.

Example of control with frequency converter:

The emv filters (EMC filters) are usually integrated at the frequency converter, but the output filters are often missing or must be ordered seperately from the manufacturer. However, third-party products can also be used.