Power Wiring 4-1
MN762
Chapter 4
Power Wiring
4.1 Overview of Power Connections
The recommended grounding method is shown in Figure 4-1.
4.1.1 Safety Ground - (G)
This is the safety ground for the drive that is required by code. One of these points must be connected to adjacent building
steel (girder, joist), a floor ground rod, or bus bar. Grounding points must comply with national and local industrial safety
regulations and/or electrical codes.
Figure 4-1 Recommended System Grounding
L1
AC Main
Supply
Safety
Ground
Driven Earth
Ground Rod
(Plant Ground)
Four Wire
Wye
L1
L2
L3
Earth
L2L3
U V W
Optional
Line
Reactor
Optional
Load
Reactor
Route all 4 wires L1, L2, L3 and Earth (Ground)
together in conduit or cable.
Route all 4 wires U, V, W and Motor Ground together
in conduit or cable.
Connect all wires (including motor ground)
inside the motor terminal box.
Ground per NEC and
Local codes.
Note: Wiring shown for clarity of grounding
Method only. Not representative of
actual terminal block location.
Note: A load reactor is recommended
and must be purchased separately.
.
Note: A line reactor is recommended
and must be purchased separately.
.
Drive
See recommended tightening torques in Table 4-1.
Use UL Listed fork terminals for ground connections.
4.1.2 Motor Ground
The motor ground must be connected to one of the ground terminals on the drive. Use UL Listed fork terminals for ground
connections.
4.1.3 Shield Termination
Either of the safety ground terminals located on the power terminal block provides a grounding point for the motor cable
shield. The motor cable shield connected to one of these terminals (drive end) should also be connected to the motor frame
(motor end). Use a shield terminating or EMI clamp to connect the shield to the safety ground terminal. When shielded cable
is used for control and signal wiring, the shield should be grounded at the drive end only, never at both ends.
4.1.4 RFI Filter Grounding
Using single-phase drives with integral filter, or an external filter with any drive rating, may result in relatively high ground
leakage currents. Therefore, the filter must only be used in installations with grounded AC supply systems and be
permanently installed and solidly grounded (bonded) to the building power distribution ground.
Ensure that the incoming supply neutral is solidly connected (bonded) to the same building power distribution ground.
Grounding must not rely on flexible cables and should not include any form of plug or socket that would permit inadvertent
disconnection. Some local codes may require redundant ground connections. The integrity of all connections should be
checked periodically.
4.2 Power Disconnect
A power disconnect should be installed between the input power service and the drive for a fail safe method to disconnect
power. The drive will remain in a powered-up condition until all input power is removed from the drive and the internal bus
voltage is depleted.
