OUTPUT FILTERING


The output stage of a drive takes a three-phase AC output with variable frequency and amplitude for fine speed and torque control and filters it to minimise EMI and provide reliable operation of the power converter and load. Ferrite cores reduce EMI caused by the switching (e.g. a switching frequency of 10kHz leads to EMI of 1MHz).


Filters such as motor chokes, sine-wave filters and SineFormer® filters are complete solutions providing optimisation for


demanding applications with long cable lengths from the output to the motor. Filtering on the output can also be performed by discrete AC capacitors.


Finally, Y capacitors are used to filter out common-mode noise and are selected to ensure they do not short-circuit and thus protect against shock to the user.


EMI filters • Ferrite cores


Optimised filters • Motor chokes • Sine-wave filters • SineFormer®


THERMAL MANAGEMENT


In a drive, the heatsink’s role is to cool the semiconductors and DC link capacitors and prevent overheating. Where no other temperature measurement is possible (i.e. wafer NTC inside the semiconductor module), the temperature of the semiconductors must be determined by means of the heatsink temperature. NTC thermistors are an effective temperature sensor to accurately measure the temperature of the heatsink.


Temperature measurement • NTC thermistors


Discrete capacitors • AC capacitors


filters


Safety capacitors • Y capacitors


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