Danfoss VLT AutomationDrive FC 300, Руководство по конструкции

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3.6 Galvanic Isolation (PELV)
3.6.1 PELV - Protective Extra Low Voltage
WARNING
Installation at high altitude:
380–500 V, enclosure D, E, and F: At altitudes above
10,000 ft [3 km], contact Danfoss regarding PELV.
WARNING
Touching the electrical parts could be fatal - even after
the equipment has been disconnected from line power.
Before touching any electrical parts, wait at least the
amount of time indicated in
chapter 2.1 Safety
Precautions .
Shorter time is allowed only if indicated on the specific
unit’s nameplate.
Also make sure that other voltage inputs have been
disconnected.
Protection against electric shock is ensured when the
electrical supply is of the PELV type and the installation
complies with local/national regulations on PELV supplies.
All control terminals and relay terminals 01-03/04-06
comply with PELV. Galvanic isolation is obtained by
fulfilling requirements for higher isolation and by providing
the relevant creepage/clearance distances. These
requirements are described in the EN 61800-5-1 standard.
To maintain PELV, all connections made to the control
terminals must be PELV. The components that make up
the electrical isolation 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,
as shown in
Figure 3.27 .
1. Power supply (SMPS) including signal isolation of
U
DC
, indicating the intermediate current voltage.
2. Gate drive that runs the IGBTs (trigger
transformers/optocouplers).
3. Current transducers.
4. Optocoupler, 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 3.27 Galvanic Isolation
The functional galvanic isolation - indicated by a and b in
Figure 3.27 - is for the 24 V backup option and for the
RS-485 standard bus interface.
3.7 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, which generates a
leakage current in the ground connection. A fault current
at the adjustable frequency drive’s output power terminals
could contain a DC component that can charge the filter
capacitors and cause a transient ground current.
The ground leakage current is affected by the following:
•
RFI filtering
•
shielded motor cables
•
adjustable frequency drive power (see Figure 3.28 )
•
line distortion (see Figure 3.29 )
130BB955.12
a
b
Leakage current
Motor cable length
Figure 3.28 Influence of the Cable Length and Power Size on
the Leakage Current
Product Introduction Design Guide
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