2 Engineering
2.4 Safety and switching
DB1 variable frequency drive
11/20 MN040031EN
Eaton.com
39
2.4.2 Fuses
The DB1 variable frequency drive and the corresponding supply cables must
be protected from thermal overload and short-circuits.
The fuses will protect the supply cable in the event of a short-circuit, limit any
damage to the variable frequency drive, and prevent damage to upstream
devices in the event of a short-circuit in the variable frequency drive.
2.4.3 Residual current device (RCD)
When using variable frequency drives DB1-
3
… that work with a three-phase
power supply (L1, L2, L3), ensure that only type B sensitive residual current
devices are used.
When using variable frequency drives that work with a single-phase power
supply (L, N) DB1-
1
2… type F and type B residual current devices may be
used.
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,
•
the symmetry of the supply system.
Other protective measures against direct and indirect contact can be used for
DB1 variable frequency drives, including isolating them from the supply sys-
tem with the use of a transformer.
￫
The fuse ratings and cable cross-sectional areas (wire gauges)
for the connection on the mains side will depend on the DB1
variable frequency drive’s input current I
LN
.
￫
For the recommended fuse sizing and assignment, see
section 5.4, “Fuses”, page 99.
WARNING
Residual current devices (RCD) may only be installed between the
supply system (AC mains supply) and the DB1 variable frequency
drive – they must never be installed in the output to the motor!