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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), with the

exception of grounded Delta leg above 400 V.

Galvanic (ensured) 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.

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 6 locations

(see Illustration 2.34):

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 voltage of intermediate DC-link

circuit.

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.

7. Mechanical brake.

130BC968.10

25 4

Illustration 2.34 Galvanic Isolation

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.

WARNING

Installation at high altitude:

380-500 V, enclosure types A, B and C: At altitudes

above 2 km, contact Danfoss regarding PELV.

525-690 V: At altitudes above 2 km, 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 Table 2.19.

Shorter time is allowed only if indicated on the

nameplate for the specific unit.

2.11 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 generates 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.

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