Operating instructions

VLT

5000 FLUX

Installation

■ Extra protection (RCD)

ELCB relays, multiple protective earthing or earthing

can be used as extra protection, provided that local

safety regulations are complied with.

In the case of an earth fault, a DC content may

develop in the faulty current.

If ELCB relays are used, local regulations must be

observed. Relays must be suitable for protection

of 3-phase equipment with a bridge rectifier and

for a brief discharge on power-up.

■ Earth leakage current

Earth leakage current is primarily caused by the

capacitance between motor phases and the motor

cable screen. When an RFI filter is used, this

contributes additional leakage current, as the filter

circuit is connected to earth through capacitors.

The size of the leakage current to the ground depends

on the following factors, in order of priority:

1. Length of motor cable

2. Motor cable with or without screen

3. Switching frequency

4. RFI filter used or not

5. Motor grounded on site or not

The leakage current is of importance to safety during

handling/operation of the frequency converter if (by

mistake) the frequency converter has not been earthed.

NB!:

Since the leakage current is >3.5 mA, reinforced

earthing must be established, which is required

if EN 50178 is to be complied with. For

3-phased frequency converters, only fault current

relays which are suitable for protection against DC

currents (Din VDE 0664) are to be used. RCD fault

current relays type B comply with these requirements

according to the norm IEC 755-2.

The following requirements must be complied with:

- Suitable for protecting equipment with a

direct current content (DC) in the fault

current (3-phase rectifier)

- Suitable for power-up with short pulse-shaped

charging current to earth

- Suitable for a high leakage current.

MG.55.A7.02 - VLT is a registered Danfoss trademark