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The leakage current also depends on the line distortion
130BB956.10
Leakage current [mA]
THVD=0%
THVD=5%
Illustration 3.11 How the leakage current is influenced by line
distortion.
NOTE
When a filter is used, turn off
14-50 RFI Filter
when
charging the filter, to avoid that a high leakage current
makes the RCD switch.
EN/IEC61800-5-1 (Power Drive System Product Standard)
requires special care if the leakage current exceeds 3.5mA.
Earth grounding must be reinforced in one of the
following ways:
•
Earth ground wire (terminal 95) of at least 10mm
2
•
Two separate earth ground wires both complying
with the dimensioning rules
See EN/IEC61800-5-1 and EN50178 for further information.
Using RCDs
Where residual current devices (RCDs), also known as earth
leakage circuit breakers (ELCBs), are used, comply with the
following:
Use RCDs of type B only which are capable of
detecting AC and DC currents
Use RCDs with an inrush delay to prevent faults
due to transient earth currents
Dimension RCDs according to the system configu-
ration and environmental considerations
L
leakage
[mA]
f [Hz]
f
sw
Cable
f
s
150 Hz
3rd harmonics
50 Hz
Mains
130BB958.10
RCD with low f
cut-off
RCD with high f
cut-off
Illustration 3.12 Main Contributions to Leakage Current.
Leakage current [mA]
100 Hz
130BB957.10
2 kHz
100 kHz
Illustration 3.13 The influence of the cut-off frequency of the
RCD on what is responded to/measured.
See also RCD Application Note, MN.90.GX.02.
3.8 Brake Functions in FC 300
Braking function is applied for braking the load on the
motor shaft, either as dynamic braking or static braking.
3.8.1 Mechanical Holding Brake
A mechanical holding brake mounted directly on the
motor shaft normally performs static braking. In some
applications the static holding torque is working as static
holding of the motor shaft (usually synchronous
permanent motors). A holding brake is either controlled by
a PLC or directly by a digital output from the frequency
converter (relay or solid state).
When the holding brake is included in a safety chain:
A frequency converter cannot provide a safe control of a
mechanical brake. A redundancy circuitry for the brake
control must be included in the total installation.
Introduction to FC 300
FC 300 Design Guide
42
MG.33.BD.02 - VLT
®
is a registered Danfoss trademark
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