3.6.1 PELV - Protective Extra Low Voltage
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 regulations on PELV
supplies.
All control terminals and relay terminals 01-03/04-06
comply with PELV (Protective Extra Low Voltage) (Does not
apply to grounded Delta leg above 400V).
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 requirements 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
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
DC
,
indicating the intermediate current 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.
130BA056.10
1
3
2
5
4
6
b
a
M
Illustration 3.9 Galvanic Isolation
The functional galvanic isolation (a and b on drawing) is
for the 24V back-up option and for the RS485 standard bus
interface.
WARNING
Installation at high altitude:
380 - 500V, enclosure A, B and C: At altitudes above 2km,
please contact Danfoss regarding PELV.
380 - 500V, enclosure D, E and F: At altitudes above 3km,
please contact Danfoss regarding PELV.
525 - 690V: At altitudes above 2km, please contact Danfoss
regarding PELV.
WARNING
Touching the electrical parts could be fatal - even after the
equipment has been disconnected from mains.
Also make sure that other voltage inputs have been
disconnected, such as load sharing (linkage of DC
intermediate circuit), as well as the motor connection for
kinetic back-up.
Before touching any electrical parts, wait at least the
amount of time indicated in the
Safety Precautions
section.
Shorter time is allowed only if indicated on the nameplate
for the specific unit.
3.7.1 Earth Leakage Current
Follow national and local codes regarding protective
earthing of equipment with a leakage current > 3,5 mA.
Frequency converter technology implies high frequency
switching at high power. This will generate a leakage
current in the earth connection. A fault current in the
frequency converter at the output power terminals might
contain a DC component which can charge the filter
capacitors and cause a transient earth current.
The earth leakage current is made up of several contri-
butions and depends on various system configurations
including RFI filtering, screened motor cables, and
frequency converter power.
a
b
130BB955.10
Cable length [m]
Leakage current [mA]
Illustration 3.10 How the leakage current is influenced by the
cable length and power size. Pa > Pb.
Introduction to FC 300
FC 300 Design Guide
MG.33.BD.02 - VLT
®
is a registered Danfoss trademark
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