Should variable-speed AC and DC motor drives be used with screened cables?
Variable-speed AC and DC motor drives must use screened motor cables, and the screens must be electrically bonded at both ends.
If screened cables are not used then the frequency inverter will probably not conform with EMC conducted emmissions limits.
In the case of an AC drive, at the drive end the screen should make a direct metal-to-metal connection (with metal saddleclamps or EMC glands) to the same metal plate that the drive’s heatsink (and mains filter) is mounted on. At the motor end, the saddleclamp or gland should bond the screen to the motor’s metal terminal box. Never use a motor with a plastic terminal box.
The only exceptions to this rule are when AC drives are fitted with sinusoidal filters, with the filter bodies making direct metal-to-metal connection to the same metal plate that the drive’s heatsink (and mains filter) is mounted on.← Back to FAQs