45
MG.30.A7.02 - VLT
®
is a registered Danfoss trademark
The VLT
®
’s voltage is dangerous when it is
connected to the mains supply and for up
to 14 minutes after disconnection of the
VLT
®
. Electrical installation may therefore
only be carried out by an authorized techni-
cian.
Warning
Incorrect installation of the motor or VLT
®
can damage equipment and cause
serious injury or death. Therefore comply
with the instructions in this manual, as
well as local and national safety regula-
tions.
Note:
It is the responsibility of the user or
technician to ensure correct earthing and
protection according to current local and
national standards.
Pre-fuses
General
The terminals for the 3-phase supply and
the motor are placed in the lowest section
of the VLT
®
’s enclosure.
The motor cable’s screen is connected to
both the VLT
®
and the motor. The VLT
®
has been tested with a given length of
screened cable and a particular cross-
section. If the cross-section is increased,
the capacitance leakage of the cable
increases and thereby the discharge
current. The length must be reduced
For VLT
®
types 3002-3052, external pre-
fuses must be installed in the current
supply to the frequency converter.
The technical data section on pp. 23-27
states correct size and dimensioning.
For VLT
®
types 3032-3052, 230 V, and
VLT
®
types 3060-3250, pre-fuses are
included in the VLT
®
’s mains connection.
proportionally. The electronic thermal relay
(ETR) in UL-approved VLT
®
frequency
converters is UL-approved for single-
motor application when parameter 315 is
set at trip, parameter 311 at “0 sec.” and
parameter 107 programmed for the
motor’s nominal current (read on the
motor’s type plate).
Electrical installation
A high voltage test can be performed by
short-circuiting terminals U, V, W, L
1
, L
2
,
L
3
, and impressing 2.5 kW D.C. for 1
second between this short circuit and the
chassis.
After the high voltage test, the filter con-
densers should be discharged using a
resistor of e.g. 100 ohm, 1/4 W- 1/2 W.
The resistors is placed bD.C. bus
to the chassis and -D.C. bus to the chas-
sis, for a few seconds.
High voltage test
Error voltage relays, or neutral earthing,
current in the discharged current.
Any ELCB relays used must comply with
local regulations.
The relays must be suitable to protect 3-
phase equipment with bridge rectifier and
short discharge on power-up.
See also the section on discharge currents
on
p.
128.
Extra protection
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