Danfoss FCM 300 Series User Manual

FCM 300 Series
MG.03.B6.02 - VLT is a registered Danfoss trademark84
■ Galvanic isolation (PELV)
PELV offers protection by way of extra low voltage.
Protection against electric shock is considered to be
ensured when all connected devices are of the
PELV type and the installation is made as described
in local/national regulations on PELV supplies.
In FCM 300 Series all control terminals are supplied
from or in connection with extra low voltage (PELV).
Galvanic (ensured) isolation is obtained by fulfilling
requirements concerning higher isolation and by
providing the relevant creapage/clearance
distances. These requirements are described in the
EN 50178 standard.
The components that make up the electrical isolation,
as described below, also comply with the
requirements concerning higher isolation and the
relevant test as described in EN 50178.
The galvanic isolation can be shown in three locations
(see drawing below), namely:
1. Power supply (SMPS) incl. signal isolation of
U
DC
, indicating the intermediate current voltage.
2. Gate drive that runs the IGBTs (opto-couplers).
3. Current transducers (opto-couplers).
■■
■■
■ Earth leakage current
Earth leakage current is primarily caused by the
capacitance between motor phases and the motor
frame. The RFI filter 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. Switching frequency
2. 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
(approx. 4-20 mA), reinforced earthing must
be established (see Quick Guide
MG.03.A1.02), which is required if EN 50178 is to
be complied with. Never use ELCB relays that are
not suitable for DC fault currents (type A).
If ELCB relays are used, they must be:
- Suitable for protecting equipment with a direct
current content (DC) in the fault current (3-phase
bridge rectifier)
- Suitable for power-up with short charging
current to earth
- Suitable for a high leakage current.
Special conditions
Galvanic isolation

Danfoss FCM 300 Series Specifications

General

Brand	Danfoss
Model	FCM 300 Series
Category	Media Converter
Language	English