Why Do VFDs Need Quality Power Cables?
VFDs are inherently noisy devices because the output IGBTs are switching hundreds of volts on and off, thousands of times per second. Because of this reality, proper cabling and grounding techniques must be followed to mitigate the potential negative effects of this operation.
Similar to encoder feedback cables, motor power cables that connect a VFD to a three-phase motor should have these proper characteristics to efficiently conduct the current, while not interfering with other electrical components in the machine.
Proper Cable Shielding
Shielding mitigates the effects of electromagnetic interference (EMI) or noise. One of the most effective and robust ways to shield the power cable is with wire mesh shielding. It is highly conductive and the mesh design helps prevent rips or breaks. EMI filters and harmonic filters are often used to further smooth out incoming and outgoing power, especially in high-power applications or when sensitive electronics are nearby.
Related Article: 7 Steps to Reducing EMI with VFDs
Benefits of High Strand Cabling
The “skin effect” is an electromagnetic principle that causes the current to concentrate on the surface of the conductor or wire, especially at high speeds. If there is not sufficient enough area to carry the current, it will find an alternative path and could cause operational issues or hardware damage.
Hundreds or thousands of strands make up high strand cabling which provides a much greater surface area than a solid conductor or standard strand cabling.
Follow the Manufacturer’s Guidelines
Even if the highest quality cable is used it can be defeated if not installed properly. Shields and grounds should be connected at the drive and motor. Wiring for the machine’s PLC or IPC control components should be run separate from the motor power cable in order to prevent signal noise. Cable environment, bend radius, and other factors should be considered for where and how the cable is run.
Contact KEB for VFD Power Cables
Selecting a high quality motor cable and installing it properly will help prevent nuisance trips or hardware damage that can be caused by EMI. If you would like more information on VFD power cables, please contact an application engineer at KEB America.
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