2 Engineering
2.4 Safety and switching
DC1 Variable Frequency Drive 04/16 MN04020003Z-EN www.eaton.com 41
2.4.3 Residual current circuit-breaker (RCD)
When using variable frequency drives (DC1-3…) that work with a three-
phase power supply (L1, L2, L3), make sure to use type B AC/DC sensitive
residual current devices exclusively.
When using variable frequency drives that work with a single-phase power
supply (L, N) (DC1-12… and DC1-1D…), you may use type A and type B
residual current devices (RCD).
The leakage currents’ magnitude will generally depend on:
• length of the motor cable,
• shielding of the motor cable,
• height of the switching frequency (switching frequency of the inverter),
• design of the radio interference suppression filter
• grounding measures at the site of the motor.
Other protective measures against direct and indirect contact can be used for
DC1 variable frequency drives, including isolating them from the supply
system with the use of a transformer.
2.4.4 Mains contactors
The mains contactor enables an operational switching on and off of the
supply voltage for the variable frequency drive and switching off in case of a
fault. The mains contactor is designed based on the mains-side input current
I
LN
of the DC1 variable frequency drive for utilization category AC-1
(IEC 60947) and the ambient air temperature at the location of use.
NOTICE
Residual current circuit-breakers (RCD = residual current device)
should
only be installed between
the power feed system
(the AC
supply system supplying power) and the DC1 variable frequency
drive – but not at the output to the motor!
￫
While planning the project, please make sure that inching
operation is not done via the mains contactor of the variable
frequency drive on frequency-controlled drives, but through a
controller input of the variable frequency drive.
The maximum permissible mains voltage switch-on frequency
for the
DC1
variable frequency drive
is once every
30 seconds
(normal operation).
￫
For UL-compliant installation and during operation, the mains
side switching devices must allow for a 1.25 times higher input
current.
￫
For the rated mains contactors for DC1 variable frequency
drives, please refer to Section 6.6, “Mains contactors“,
page 148.
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