MOTOR CHOKES AND FILTERS

n many applications motor chokes help to achieve the optimum performance - either because the motor inductance needs to be adjusted to the amplifier or because the motor current need to be filtered for lower ripple and therefore smoother operation or better EMC behaviour.

In addition to several standard components we also can offer custom versions. The following motor chokes are available as standard:

  • L100/3K: 1mH, nominal current 3A, DxH 45 x 30mm (plus connector), 0.25kg
  • L020/6K: 0.2mH, nominal current 6A, DxH 45 x 30mm (plus connector), 0.25kg
  • L050/8K: 0.5mH, nominal current 8A, DxH 60 x 41mm (plus connector), 0.6kg
  • L012/20K: 0.12mH, nominal current 20A, DxH 60 x 41mm (plus connector), 0.6kg

Something special is the motor filter of Copley: Most noise is capacitively coupled from the motor power cable to neighboring cables. To minimize this noise, the XTL-FA-01 edge filter uses both differential edge filtering and common mode filtering. Differential edge filtering reduces the high frequency component of the PWM signal, thus producing a signal with less energy that can be coupled during transmission. Common mode filtering reduces the unnecessary common mode noise generated by PWM signals.

The differential filter increases the rise time by at least a factor of 3, substantially reducing noise in the system. Copley Controls amplifiers typically have a 150 ns-rise time (high frequency component in the MHz range). Thus, the edge filter can increase rise time to 500 ns, reducing the high frequency noise emissions by the square law. The differential filter is designed with 82 CH
inductors and a proprietary passive circuit. The inductance will provide a total of 164CH in series with the load, helping to reduce ripple current. This brings low inductance motors into the required range.