What’s the importance of Purpose-designed VFD Cable?

Electrical energy flowing in the cable contains frequencies as high as 30 megahertz. If this radio frequency energy is not contained within the cable, it can radiate out to interfere with the proper operation of nearby electronic equipment, less-than-robust, or commercial-grade Ethernet systems, and simple instrumentation wires — even circuits that have absolutely nothing to do with the VFD system itself.

This noise emission can sometimes be very difficult to track down and eliminate and is likely the single most significant problem associated with VFD systems today. Unless a proper cable shielding design is present to control it, noise emission from a drive system cable can disrupt plant and factory operations. Moreover, because a longer cable radiates more noise, the length of cable runs must be limited. That, in turn, puts a limitation on factory layout.

Instrument Cable Pakistan

There is another potentially serious concern with use of VFDs: With an improperly selected cable, voltage waves reflected back from the motor toward the VFD along the cable can produce excessively high voltages in the cable's conductors, because they add to the voltage that is already there.

Peak voltages of up to 2.5 times the nominal system voltage are sometimes present in the cable. As a result, voltage reflections have been known to cause a number of in-service motor failures. There is also some concern over possible long-term cable damage under high voltage — especially with #VFDs operating at 575 volts and above.In addition, high voltage levels in the #cable can sometimes cause a corona discharge to occur between the conductors, an effect that can damage not only the cable itself but also the #motor, motor #bearings and the #drive. This can lead to failure of the entire system, with ensuing production downtime.

The problems of noise emissions, voltage reflections, over voltages, and corona discharge can be substantially reduced or even avoided by choosing the appropriate VFD cable. The topic related to selection of cable will be covered in next note.