Industrial Engineer · phase 13 of 16
Bonding
Low-impedance connection of drive, enclosure, cable shield, and motor frame to control fault and high-frequency currents.
The Explain card
- Plain English
- Bonding is connecting the drive, its enclosure, the cable shield and the motor frame together with low impedance at high frequency. Long thin green wires are fine for 60 hertz and nearly useless for the frequencies PWM produces.
- Example
- A cable shield is terminated with a 360 degree clamp at the drive and at the motor, and the motor frame is bonded to the drive backplane with a wide flat strap. The common mode current now has a short loop.
- Why it matters
- Most drive noise problems are bonding problems, and they show up as interference, nuisance trips and bearing damage. Wide, short and flat are the rules, and a pigtail on a shield undoes the shield.
- Hook
- Give the noise a short way home or it will find a long one.
Where it sits in the deck
Phase 13: VFD Power Quality, Wiring, and Motor Protection
Harmonics, reflected waves, shielded cable and bearing currents: the side effects a drive inflicts on everything around it.
