Danfoss VLT 2800 Operations Instructions download pdf (Page 12)

1.4.6 Motor Cables

See

General Specifications

for correct dimensioning of motor cable cross-section and length. See

EMC Emissions

for relationship between length and EMC emission.

Always comply with national and local regulations on cable cross-section.

NB!

If an unscreened/unarmoured cable is used, some EMC requirements are not com-

plied with, see

EMC test results

in the Design Guide.

If the EMC specifications regarding emission are to be complied with, the motor cable must be

screened/armoured, unless otherwise stated for the RFI filter in question. It is important to keep

the motor cable as short as possible so as to reduce the noise level and leakage currents to a

minimum. The motor cable screen must be connected to the metal cabinet of the frequency con-

verter and to the metal cabinet of the motor. The screen connections are to be made with the

biggest possible surface area (cable clamp). This is enabled by different installation devices in

different frequency converters. Mounting with twisted screen ends (pigtails) is to be avoided, since

these spoil the screening effect at high frequencies. If it is necessary to break the screen to install

a motor isolator or motor relay, the screen must be continued at the lowest possible HF impedance.

1.4.7 Motor Thermal Protection

The electronic thermal relay in UL-approved frequency converters has received the UL-approval

for single motor protection, when parameter 128

Motor thermal protection

has been set for

ETR

Trip

and parameter 105

Motor current, I

M, N

has been programmed to the rated motor current

(see motor nameplate).

1.4.8 Control Cables

Remove the front cover underneath the control panel. Place a jumper between terminals 12 and

27.

Control cables must be screened/armoured. The screen must be connected to the frequency con-

verter chassis by means of a clamp. Normally, the screen must also be connected to the chassis

of the controlling unit (use the instructions for the unit in question). In connection with very long

control cables and analogue signals, in rare cases depending on the installation, 50/60 Hz earth

loops may occur because of noise transmitted from mains supply cables. In this connection, it may

be necessary to break the screen and possibly insert a 100 nF capacitor between the screen and

the chassis.

See section entitled

Earthing of screened/armoured control cables

in the VLT 2800 Design Guide

for the correct termination of control cables.

VLT 2800 Quick Guide 1 Quick Guide

MG.28.M1.02 - VLT

is a registered Danfoss trademark

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Danfoss VLT 2800 Operations Instructions Page 12

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