Electrical Engineering - DC supply decoupling

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DC supply decoupling

2006-04-19, 7:21 am

We are refurbishing a machine which uses an inverter to run a motor.
This is geared down to a rotating plate. the number of rotations of
this plate is counted using an encoder and digital counter.

We are getting a lot of interference on the counter and in certain
encoder positions it counts up/down rapidly when no movement is
occuring. The old machine is badly wired with motor cables routed
alongside control cables.

We have been separating the control cables from the inverter cables but
the problem is still happening. It seems now that the inverter is
affecting the DC supply to the encoder and that it is this which is
causing the interference.

I remember in the past that it has been possible to decouple across DC
lines with capacitors to help remove noise. However I can not remember
capacitor types/sizes which are most suitable. Does anyone have any
ideas on which will be best?

I know that this is not the nest solution and ripping out all the old
wiring and replacing it would be better, however at the moment this is
the only viable solution due to time scales.

Thanks for your help in advance

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