Delta MS300 Series User Manual page 88

The Motor Cable Length
Consequence of leakage current on the motor
1.
If the cable length is too long, the stray capacitance between cables increases and may cause
leakage current. In this case, It activates the over-current protection, increases leakage current, or
may affect the current display. The worst case is that it may damage the AC motor drive. If more
than one motor is connected to one AC motor drive, the total wiring length should be the sum of the
wiring length from AC motor drive to each motor.
For the 460V models AC motor drive, when you install an overload thermal relay between the drive
and the motor to protect the motor from overheating, the connecting cable must be shorter than 50
m; however, an overload thermal relay malfunction may still occur. To prevent the malfunction,
install an output reactor (optional) to the drive or lower the carrier frequency setting (see Pr.00-17
Carrier Frequency).
Consequence of the surge voltage on the motor
2.
When a motor is driven by a PWM-type AC motor drive, the motor terminals experience surge
voltages (dv/dt) due to power transistor conversion of AC motor drive. When the motor cable is very
long (especially for the 460V models), surge voltages (dv/dt) may damage the motor insulation and
bearing. To prevent this, follow these rules:
Use a motor with enhanced insulation.
a.
Reduce the cable length between the AC motor drive and motor to suggested values.
b.
Connect an output reactor (optional) to the output terminals of the AC motor drive.
c.
Refer to the following tables for the suggested motor shielded cable length. For drive models <
480V, use a motor with a rated voltage ≤ 500 V
with IEC 60034-17. For the 575V drive model, use a motor with a rated voltage ≤ 600 V
insulation level ≥ 1.79 kV
110V One-phase
Drive Model
VFD1A6MS11ANSAA
VFD1A6MS11ENSAA
VFD2A5MS11ANSAA
VFD2A5MS11ENSAA
VFD4A8MS11ANSAA
VFD4A8MS11ENSAA
230V One-phase
Drive Model
VFD1A6MS21ANSAA
VFD1A6MS21ENSAA
VFD1A6MS21AFSAA
VFD2A8MS21ANSAA
VFD2A8MS21ENSAA
VFD2A8MS21AFSAA
in accordance with IEC 60034-25.
p-p
Without an AC Output Reactor
Normal Duty
Rated Current
Shielded Cable
(Arms) (meter)
1.8
2.7
5.5
Without an AC Output Reactor
Normal Duty
Rated Current
Shielded Cable
(Arms)
(meter)
1.8
3.2
79
Chapter 7 Optional AccessoriesMS300
and an insulation level ≥ 1.35 kV
AC
Non-shielded
Cable (meter)
50 75
Non-shielded
Cable (meter)
50 75
in accordance
p-p
and an
AC
With an AC Output Reactor
Shielded Non-shielded
Cable Cable
(meter) (meter)
75 115
Table 7-37
With an AC Output Reactor
Shielded Non-shielded
Cable Cable
(meter) (meter)
75 115