Chapter 3 – Installation Instructions
ACH 400 with Electronic Bypass User’s Manual 3-17
Checking Motor Wiring
and Motor Insulation
1. Check that the motor wires are disconnected from the Electronic Bypass
output on Terminals T1, T2, and T3.
2. Check that the motor wires are disconnected from the motor and remove
bridging connections at the motor.
3. Measure the insulation resistances of the motor. The voltage range of the
insulation resistance meter must be at least equal to the line voltage, but
not exceeding 1000 V. The insulation resistance must be greater than
1MΩ.
4. Measure the insulation resistance of the motor wiring between the phases
and between each phase and ground. The insulation resistance must be
greater than 1 MΩ.
Connection Points Connect the motor cables to the output terminal block as shown in Figures
3-1 and 3-3. The motor grounding conductor can be connected to the ground
lug near the terminal block.
Note: Do not connect the motor wires before proceeding with the Keypad
Control Test, Motor Disconnected. Refer to Keypad Control Tests,
Chapter 4 – Start-up Procedure, in this manual.
Motor Cable Length The rapid rate of voltage changes causes capacitive coupling between motor
wiring and the grounded metallic conduit. This phenomenon can cause
substantially higher measured current than actual motor current, which may
result in nuisance overcurrent trips or ground faults. Table 3-3 lists the
maximum motor cable length based on capacitive coupling. It may also be
necessary to consider motor insulation requirements related to drive output
dv/dt.
Table 3-3 Maximum Recommended Motor Wire Lengths
Control Wiring The control wiring includes connections to an analog speed command signal
and a start/stop relay contact for controlling the motor in the AUTO mode.
There may also be connections to external run enable interlock contacts and a
connection from the Motor Run contact to an external status indicating circuit.
For a detailed description of the control circuit functions, refer to the section
entitled Detailed Description of Operation on page 2-5.
Frame Size
Maximum Cable Length
Feet Meters
R1 330 100
R2, R3 & R4 660 200
R5, R6, R7, R8 & R9 990 300
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