Touch Current - Danfoss VLT ISD 510 Design Manual

System Integration
Using RCDs
Where residual current devices (RCDs), also known as earth
leakage circuit breakers (ELCBs), are used, comply with the
following:
•
Only use type B RCDs, as they are capable of
detecting AC and DC currents.
•
Use RCDs with a delay to prevent faults due to
transient ground currents.
4 4
•
Dimension RCDs according to the system configu-
ration and environmental considerations.
The leakage current includes several frequencies
originating from both the mains frequency and the
switching frequency. Whether the switching frequency is
detected depends on the type of RCD used.
Leakage current
50 Hz
Mains
Illustration 4.3 Main Contributions to Leakage Current
The amount of leakage current detected by the RCD
depends on the cut-off frequency of the RCD.
Leakage current [mA]
Illustration 4.4 Influence of RCD Cut-off Frequency on Leakage
Current
40
VLT
RCD with low f
cut-
RCD with high f
cut-
150 Hz f
3rd harmonics Cable
100 Hz
2 kHz
100 kHz
Danfoss A/S © 08/2017 All rights reserved.
®
Integrated Servo Drive ISD

4.3.2.7 Touch Current

The purpose of the touch current is to test if the leakage
current in the protective earth (PE) of the power drive
system is less than 3.5 mA AC or 10 mA DC.
If the leakage current is below or equal to 3.5 mA AC or
10 mA DC, no special measures relating to the PE
connection are required.
The leakage current of the VLT
ISD 510 System is greater than 3.5 mA AC or 10 mA DC,
therefore a fixed connection is required and 1 or more of
the following conditions must be satisfied when installing
the DUT:
1.
2.
3.
WARNING
Frequency
LEAKAGE/GROUNDING CURRENT HAZARD
sw
Leakage/grounding currents are >3.5 mA. Failure to
ground the SAB and the servo drives properly could
result in death or serious injury.
•
®
510 System
®
Integrated Servo Drive
A cross-section of the protective earthing
conductor of at least 10 mm² Cu or 16 mm² Al.
Automatic disconnection of the supply in case of
discontinuity of the protective earthing
conductor.
Provision of an additional terminal for a
protective earthing conductor of the same cross-
sectional area as the original protective earthing
conductor.
Ensure the correct grounding of the SAB and
servo drives by a certified electrical installer in
accordance with applicable national and local
electrical standards and directives, and the
instructions contained in this manual.
MG36C102