Phase Motion Control
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Standard Products

Anti-resonance Filter

In some conditions of the power supply chain, electrical resonance phenomena may occur in motor windings.

These phenomena can multiply several times the instantaneous voltage of winding versus ground, leading to excessive stress of the motor insulation system resulting in quick degeneration and total insulation failure after a short time of operation.


EN ISO 13849-1:2015 , EN 62061:2005

Picture below shows the star point voltage versus ground waveform acquired in a system with significant resonance. The DC-Bus setting of the power amplifier is only 600 Vdc but the instantaneous voltage can reach a value as high as 1600 V. The insulation system cannot withstand this high voltage in long term operation.

To limit such voltage transients, Phase supplies with each motor with such characteristics a tuned anti resonance filter (snubber) which must be assembled within 5 m of the motors, star terminal (white wire) and machine ground. Failure to connect the snubber may result in motor failure by insulator puncturing. Phase can supply different type of snubber depending on motor size.

NOTE: larger snubbers in normal opera 200W) and need to be mounted on a cooling surface. Check this requirement on the snubber drawing.

Also PMC suggest , in the first installation, to check the temperature of the snubber that do not exceed 90°C.

On request Phase can supply special snubbers with a channel for liquid cooling.


The values of snubber filter are calculated for a “typical” configuration. The actual configuration of the complete power supply chain (inverter PWM modulation method, type and length of the supply cables, type of series inductor and/or filter installed) can modify significantly the behaviour of the system. Consequently it is strongly recommended that for each first installation of a new motor type or significant modification of the power supply components (such as different power amplifier type or brand) the star point voltage potential to ground with supplied snubber connected is acquired. The peak value must be