Danfoss VLT 8000 AQUA Przewodnik Instalacji Pobierz pdf (Strona 25)

VLT® 8000 AQUA

Installation

The total current consumption of the motors

is not to exceed the maximum rated output

current I

VLT,N

for the AFD.

Problems may arise at the start and at low rpm values if

the motor sizes are widely different. This is because the

relatively high ohmic resistance in small motors calls for

a higher voltage at the start and at low rpm values.

In systems with motors connected in parallel, the

electronic thermal relay (ETR) of the AFD cannot

be used as motor protection for the individual

motor. Consequently, additional motor protection

is required, such as thermistors in ground motor

(or individual thermal relays).

NOTE

Parameter 107 Automatic Motor Adaptation,

AMA and Automatic Energy Optimization, AEO

in parameter 101 Torque characteristics cannot

be used motors are connected in parallel.

■ Motor cables

See Technical data for correct sizing of motor

cable cross-section and length.

Always comply with national and local regulations

on cable cross-sections.

NOTE

If an unshielded cable is used, some

EMC requirements are not complied with,

see EMC test results.

If the EMC specifications regarding emission are

to be complied with, the motor cable must be

shielded, 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 shield must be connected to the

metal cabinet of the AFD and to the metal cabinet of

the motor. The shield connections are to be made

with the biggest possible surface (cable clamp).

This is enabled by different installation devices in

the different AFDs. Mounting with twisted shield

ends (pigtails) is to be avoided, since these spoil

the shielding effect at higher frequencies.

If it is necessary to break the shield to install a

motor isolator or motor contactor, the shield must be

continued at the lowest possible HF impedance.

MG.80.A6.22 - VLT is a registered Danfoss trademark

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Danfoss VLT 8000 AQUA Przewodnik Instalacji Strona 25

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