Danfoss FC 300 Design Manual page 39

FC 300 Design Guide
Galvanic Isolation (PELV)
PELV offers protection by way of extra low voltage. Protection against electric shock is ensured when
the electrical supply is of the PELV type and the installation is made as described in local/national regu-
lations on PELV supplies.
All control terminals and relay terminals 01-03/04-06 comply with PELV (Protective Extra Low Voltage)
(Does not apply to 525-600 V units and at grounded Delta leg above 300 V).
Galvanic (ensured) isolation is obtained by fulfilling requirements for higher isolation and by providing
the relevant creapage/clearance distances. These requirements are described in the EN 61800-5-1
standard.
The components that make up the electrical isolation, as described below, also comply with the require-
ments for higher isolation and the relevant test as described in EN 61800-5-1.
The PELV galvanic isolation can be shown in six locations (see illustration):
In order to maintain PELV all connections made to the control terminals must be PELV, e.g. thermistor
must be reinforced/double insulated.
1. Power supply (SMPS) incl. signal isolation
of U , indicating the intermediate current
DC
voltage.
2. Gate drive that runs the IGBTs (trigger
transformers/opto-couplers).
3. Current transducers.
4. Opto-coupler, brake module.
5. Internal inrush, RFI, and temperature
measurement circuits.
6. Custom relays.
The functional galvanic isolation (a and b on drawing) is for the 24 V back-up option and for the RS 485
standard bus interface.
Introduction to FC 300
Galvanic isolation
MG.33.B7.02 - VLT is a registered Danfoss trademark
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