2.10 Galvanic Isolation (PELV)
2.10.1 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
Figure 2.32
):
In order to maintain PELV, all connections made to the
control terminals must be PELV. For example, the
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 soft-charge, RFI and temperature
measurement circuits.
6.
Custom relays.
130BA056.10
1
3
2
5
4
6
b
a
M
Figure 2.32 Galvanic Isolation
The functional galvanic isolation (a and b on drawing) is
for the 24V backup option and for the RS-485 standard bus
interface.
WARNING
Installation at high altitude:
380–500V, enclosure A, B and C: At altitudes above 6561 ft
[2 km], please contact Danfoss regarding PELV.
380–500V, enclosure D, E and F: At altitudes above 9842 ft
[3 km], please contact Danfoss regarding PELV.
525–690V: At altitudes above 6561 ft [2 km], please contact
Danfoss regarding PELV.
WARNING
Touching the electrical parts could be fatal - even after the
equipment has been disconnected from line power.
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 backup.
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.
2.11 Ground Leakage Current
Follow national and local codes regarding protective
grounding of equipment with a leakage current > 3.5 mA.
Adjustable frequency drive technology implies high
frequency switching at high power. This will generate a
leakage current in the ground connection. A fault current
in the adjustable frequency drive at the output power
terminals might contain a DC component which can
charge the filter capacitors and cause a transient ground
current.
Introduction to VLT® HVAC D...
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®
HVAC Drive Design Guide
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®
is a registered Danfoss trademark
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