Delta VFD-M-D series, User Manual, Page: 22 / 163

Chapter 2 Installation and Wiring
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VFD-M-D Series
Revision Jan. 2007, MDE2, SW V1.05 2-9
DO NOT connect phase-compensation capacitors or surge absorbers at the output terminals
of AC motor drives.
With long motor cables, high capacitive switching current peaks can cause over-current, high
leakage current or lower current readout accuracy. To prevent this, the motor cable should
be less than 20m for 3.7kW models and below. And the cable should be less than 50m for
5.5kW models and above. For longer motor cables use an AC output reactor.
Use a well-insulated motor, suitable for inverter operation.
Terminals [B1, B2] for connecting external brake unit
B2
BR
Braking resistor(optional)
Refer to Appendix B for the use of
special braking resistor
Connect a brake resistor or brake unit in applications with frequent deceleration ramps, short
deceleration time, too low braking torque or requiring increased braking torque.
The AC motor drive has a built-in brake chopper, you can connect the external brake resistor
to the terminals [B1, B2] when needed.
WARNING!
1. Short-circuiting [B2] to [B1] can damage the AC motor drive.
Grounding terminals ( )
Make sure that the leads are connected correctly and the AC drive is properly grounded.
(Ground resistance should not exceed 100
Ω
.)
Use ground leads that comply with local regulations and keep them as short as possible.
Multiple VFD-M-D units can be installed in one location. All the units should be grounded
directly to a common ground terminal, as shown in the figure below. Ensure there are no
ground loops.
good excellent
not allowed