4.1.11 How to Connect Motor - Introduction
See section
General Specifications
for correct dimensioning of
motor cable cross-section and length.
•
Use a screened/armoured motor cable to comply
with EMC emission specifications (or install the cable
in metal conduit).
•
Keep the motor cable as short as possible to reduce
the noise level and leakage currents.
•
Connect the motor cable screen/armour to both the
decoupling plate of the frequency converter and to
the metal of the motor. (Same applies to both ends
of metal conduit if used instead of screen.)
•
Make the screen connections with the largest
possible surface area (cable clamp or by using an
EMC cable gland). This is done by using the supplied
installation devices in the frequency converter.
•
Avoid terminating the screen by twisting the ends
(pigtails), as this will spoil high frequency screening
effects.
•
If it is necessary to break the continuity of the screen
to install a motor isolator or motor relay, the continu-
ity must be maintained with the lowest possible HF
impedance.
Cable length and cross-section
The frequency converter has been tested with a given length
of cable and a given cross-section of that cable. If the cross-
section is increased, the cable capacitance - and thus the
leakage current - may increase, and the cable length must be
reduced correspondingly.
Switching frequency
When frequency converters are used together with sine wave
filters to reduce the acoustic noise from a motor, the switching
frequency must be set according to the sine wave filter
instruction in par. 14-01
Switching Frequency
.
Precautions while using Aluminium conductors
Aluminium conductors are not recommended for cable cross
sections below 35 mm2. Terminals can accept aluminium
conductors but the conductor surface has to be clean and the
oxidation must be removed and sealed by neutral acid free
Vaseline grease before the conductor is connected.
Furthermore, the terminal screw must be retightened after
two days due to the softness of the aluminium. It is crucial to
ensure the connection makes a gas tight joint, otherwise the
aluminium surface will oxidize again.
All types of three-phase asynchronous standard motors can be
connected to the frequency converter. Normally, small motors
are star-connected (230/400 V, D/Y). Large motors are delta-
connected (400/690 V, D/Y). Refer to the motor name plate for
correct connection mode and voltage.
Illustration 4.16: Terminals for motor connection
CAUTION!
In motors without phase insulation paper or other
insulation reinforcement suitable for operation with
voltage supply (such as a frequency converter), fit a sine-
wave filter on the output of the frequency converter.
(Motors that comply with IEC 60034-17 do not require a
Sine-wave filter).
No.
96
97
98
Motor voltage 0-100% of mains voltage.
U
V
W
3 cables out of motor
U1
V1
W1
6 cables out of motor, Delta-connected
W2
U2
V2
U1
V1
W1
6 cables out of motor, Star-connected
U2, V2, W2 to be interconnected separate-
ly
(optional
terminal
block)
No.
99
Earth
connection
PE
Table 4.8: 3 and 6 cable motor connection.
Electrical Installation
VLT
®
HVAC Drive Operating Instructions
MG.11.AD.02 - VLT
®
is a registered Danfoss trademark
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