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Why i used dv/dt filter for VSD but still have cable lenght limite

Why i used dv/dt filter for VSD but still have cable lenght limite

Why i used dv/dt filter for VSD but still have cable lenght limite

(OP)
As i found on many seller VSD catalogue that we can extend cable lenght by use dv/dt filter for mitigation overvoltage at motor side but after we added dv/dt we can extend lenght of cable only 50 -100 m . Can we use more than ?
This limitation is for EMC standard reason or technical reason

RE: Why i used dv/dt filter for VSD but still have cable lenght limite

What size of VSD are you talking about ? In small drives the current needed to charge the cable capacitance -even at reduced dV/dt- can cause significant additional losses in the power semiconductors or it can cause overcurrent trips.

RE: Why i used dv/dt filter for VSD but still have cable lenght limite

A dv/dt filter, just like any other electrical component, has limits to it's use.  While a dv/dt filter cleans up the high frequency components in drive output pulses to some degree, the effect is not total.  Therefore, it increases the protection to the motor insulation over an increased range of lead lengths but not out to infinity.

Exactly what those limits are varies by voltage, motor hp, drive carrier frequency, motor insulation class, and other things.

This isn't a surprise now, is it?

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