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4 Electrical Installation
4.1.11 How to Connect Motor - Introduction
General Specifications
See section
•
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.
4
•
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 continuity 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
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.
NB!
In motors without phase insulation paper or other insulation reinforcement suitable for operation with voltage supply (such as a fre-
quency 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
U
U1
W2
U1
No.
99
PE
Table 4.8: 3 and 6 cable motor connection.
32
for correct dimensioning of motor cable cross-section and length.
Switching Frequency
97
98
Motor voltage 0-100% of mains voltage.
V
W
3 cables out of motor
V1
W1
6 cables out of motor, Delta-connected
U2
V2
V1
W1
6 cables out of motor, Star-connected
U2, V2, W2 to be interconnected separately
(optional terminal block)
Earth connection
IVS 102 Operating Instructions
.
Illustration 4.16: Terminals for motor connection
MG.12.E2.02
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