In the case of an earth fault, a DC content may develop in the faulty current.
If ELCB relays are used, local regulations must be observed. Relays must be suitable for protection
of 3-phase equipment with a bridge rectifier and for a brief discharge on power-up.
See also the section
Special Conditions
in the relevant Design Guide.
3.5.5. RFI Switch
Mains supply isolated from earth
If the frequency converter is supplied from an isolated mains source (IT mains, floating delta and
grounded delta) or TT/TN-S mains with grounded leg, the RFI switch is recommended to be turned
off (OFF)
1)
via par. 14-50. For further reference, see IEC 364-3. In case optimum EMC perform-
ance is needed, parallel motors are connected or the motor cable length is above 25 m, it is
recommended to set par. 14-50 to [ON].
1)
Not required with 525-600/690 V drives; therefore not possible.
In OFF, the internal RFI capacities (filter capacitors) between the chassis and the intermediate
circuit are cut off to avoid damage to the intermediate circuit and to reduce the earth capacity
currents (according to IEC 61800-3).
Please also refer to the application note
VLT on IT mains, MN.90.CX.02
. It is important to use
isolation monitors that are capable for use together with power electronics (IEC 61557-8).
3.5.6. Torque
When tightening all electrical connections it is
very important to tighten with the correct tor-
que. Too low or too high torque results in a
bad electrical connection. Use a torque
wrench to ensure correct torque
Illustration 3.79: Always use a torque wrench to
tighten the bolts.
Enclosure
Terminal
Torque
Bolt size
D1, D2, D3 and D4
Mains
Motor
19 Nm (168 in-lbs)
M10
Load sharing
Brake
9.5 (84 in-lbs)
M8
E1 and E2
Mains
Motor
Load sharing
19 NM (168 in-lbs)
M10
Brake
9.5 (84 in-lbs)
M8
Table 3.4: Torque for terminals
VLT
®
Automation Drive FC 300
Operating Instructions High Power
3. How to Install
MG.33.U1.02 - VLT
®
is a registered Danfoss trademark
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