NOTICE
Monitoring the brake power is not a safety function; a
thermal switch connected to an external contactor is
required for that purpose. The brake resistor circuit is
not ground leakage protected.
Overvoltage control (OVC)
can be selected as an alternative
brake function in
parameter 2-17 Over-voltage Control
. This
function is active for all units and ensures that if the DC-
link voltage increases, the output frequency also increases
to limit the voltage from the DC link, which avoids a trip.
NOTICE
OVC cannot be activated when running a PM motor,
while
parameter 1-10 Motor Construction
is set to
[1] PM
non-salient SPM
.
10.8 Residual Current Devices (RCD) and
Insulation Resistance Monitor (IRM)
Use RCD relays, multiple protective grounding, or
grounding as extra protection, provided they comply with
local safety regulations.
If a ground fault appears, a DC current can develop in the
faulty current. If RCD relays are used, local regulations
must be observed. Relays must be suitable for protection
of 3-phase equipment with a bridge rectifier and for a brief
discharge on power-up. See
for more details.
10.9 Leakage Current
Follow national and local codes regarding protective
grounding of equipment where leakage current exceeds
3.5 mA.
Drive technology implies high-frequency switching at high
power. This high-frequency switching generates a leakage
current in the ground connection.
The ground leakage current is made up of several contri-
butions and depends on various system configurations,
including:
•
RFI filtering.
•
Motor cable length.
•
Motor cable shielding.
•
Drive power.
130BB955.12
a
b
Leakage current
Motor cable length
Illustration 10.12 Motor cable length and power size influence
the leakage current. Power size a > power size b.
The leakage current also depends on the line distortion.
130BB956.12
THDv=0%
THDv=5%
Leakage current
Illustration 10.13 Line Distortion Influences Leakage Current
If the leakage current exceeds 3.5 mA, compliance with
EN/IEC61800-5-1 (power drive system product standard)
requires special care.
Reinforce grounding with the following protective ground
connection requirements:
•
Ground wire (terminal 95) of at least 10 mm
2
(8 AWG) cross-section.
•
2 separate ground wires both complying with the
dimensioning rules.
See EN/IEC61800-5-1 and EN 50178 for further information.
Electrical Installation Con...
VLT® AutomationDrive FC 302
158
Danfoss A/S © 01/2018 All rights reserved.
MG38C202
10
10
