Ground Wiring - YASKAWA E7 Installation Manual

Cable Length between Drive and Motor
The E7 should be installed as close as possible to the motor to minimize the length of load side power cable needed between
the Drive and the motor.
If the cable between the Drive and the motor is long, the high-frequency leakage current will increase, causing the Drive
output current to increase as well. This may affect peripheral devices. To prevent this, reduce the cable length whenever
possible, or if necessary, adjust the carrier frequency (set in C6-02) as shown in Table 2.6.
The line side power cables, load side power cables and the control wiring should all be run in a separate conduit. Careful atten-
tion to this recommended design practice will avoid many potential motor and Drive related problems.
Motor Cable Length
Carrier Frequency
(See the limitations on carrier frequency, based on Drive capacity and model number in Appendix B).

Ground Wiring

Observe the following precautions when connecting the ground wire:
1. 208-240Vac Drives should have a ground connection with resistance of less than 100Ω.
2. 480Vac Drives should have a ground connection with resistance of less than 10Ω.
3. Do not share the ground wire with other devices, such as motors or large-current electrical equipment.
4. Always use a ground wire that complies with technical standards on electrical equipment and minimize the length of the
ground wire. Leakage current flows through the Drive. Therefore, if the distance between the ground rod and the ground
terminal is too long, potential on the ground terminal of the Drive will become unstable.
5. When using more than one Drive, be careful not to loop the ground wire. See Fig 2.4.
Control Circuit Ground Terminals
The removable Drive control terminal card provides two ground terminals (marked TB3 and TB4) to accept the control wire
shield connection. The control wire shield should be connected on this end only, the opposite end should be isolated with
electrical tape.
Grounding of the E7 enclosure and motor is required for proper system operation.
IMPORTANT
Table 2.6 Motor Cable Length vs. Carrier Frequency (C6-02)
164 ft. (50m) maximum
15kHz maximum
OK
Fig 2.2 Ground Wiring Examples
Electrical Installation 2 - 11
328 ft. (100m) maximum
10kHz maximum
NO OK
More than 328 ft.(100m)
5kHz maximum
NOT OK