Earth Leakage Current; Extreme Running Conditions - Danfoss VLT FC51 Design Manual

Product Overview
0.25-22 kW
3 3
2
3
1 Power supply (SMPS)
2 Optocouplers, communication between AOC and BOC
3 Custom relays
a Control card terminals
Illustration 3.6 Galvanic Isolation
30-90 kW
4
5
1 Power supply (SMPS) incl. signal isolation of UDC, indicating
the intermediate current voltage
2 Gate drive that runs the IGBTs (trigger transformers/opto-
couplers)
3 Current transducers
4 Internal soft-charge, RFI and temperature measurement
circuits
5 Custom relays
a Control card terminals
Illustration 3.7 Galvanic Isolation
The functional galvanic isolation (see Illustration 3.6) is for
the RS-485 standard bus interface.
CAUTION
Installation at high altitude:
At altitudes above 2,000 m, contact Danfoss regarding
PELV.
24
VLT
SMPS
1
a
3
1 2
a
®
Micro Drive FC 51 Design Guide

3.4 Earth Leakage Current

WARNING
DISCHARGE TIME
M
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 2.1.
Shorter time is allowed only if indicated on the
nameplate for the specific unit.
NOTICE
Leakage Current
The earth leakage current from the frequency converter
exceeds 3.5 mA. To ensure that the ground cable has a
good mechanical connection to the ground connection,
the cable cross section must be at least 10 mm
mm 2 Al or 2 rated earth wires terminated separately.
Residual Current Device protection RCD
This product can cause a DC current in the protective
conductor. Where a residual current device (RCD) is used
M
for protection in case of direct or indirect contact, only
an RCD of Type B is allowed on the supply side of this
product. Otherwise, another protective measure shall be
applied, such as separation from the environment by
double or reinforced insulation, or isolation from the
supply system by a transformer. See also Application
Note Protection against Electrical Hazards, MN90G.
Protective earthing of the frequency converter and the
use of RCDs must always follow national and local
regulations.

3.5 Extreme Running Conditions

Short circuit (motor phase – phase)
Current measurement in each of the 3 motor phases or in
the DC-link, protects the frequency converter against short
circuts. A short circuit between 2 output phases causes an
overcurrent in the inverter. The inverter is turned off
individually when the short circuit current exceeds the
permitted value (Alarm 16 Trip Lock).
For information about protecting the frequency converter
against a short circuit at the load sharing and brake
outputs, see the design guidelines.
Switching on the output
Switching on the output between the motor and the
frequency converter is fully permitted. The frequency
converter is not damaged in any way by switching on the
output. However, fault messages may appear.
MG02K302 - Rev. 2013-12-03
2 Cu or 16