Specifications

130BB956.11
Leakage current [mA]
THVD=0%
THVD=5%
Illustration 2.30 Line Distortion Influences Leakage Current.
NOTICE
When a filter is used, turn off SP-50 RFI Filter when
charging the filter, to avoid a high leakage current
making the RCD switch.
EN/IEC61800-5-1 (Power Drive System Product Standard)
requires special care if the leakage current exceeds 3.5 mA.
Earth grounding must be reinforced in one of the
following ways:
•
Earth ground wire (terminal 95) of at least 10
mm
2
•
2 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 only RCDs of type B, 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
130BB958.11
L
leakage
[mA]
f [Hz]
f
sw
Cable
f
s
150 Hz
3rd harmonics
50 Hz
Mains
RCD with low f
cut-o
RCD with high f
cut-o
Illustration 2.31 Mains Contributions to Leakage Current.
130BB957.11
Leakage current [mA]
100 Hz
2 kHz
100 kHz
Illustration 2.32 Effect of the RCD frequency
See the RCD Application Note for more information.
2.12 Brake Function
2.12.1 Brake Resistor Selection
In certain applications (in a tunnel or underground railway
station ventilation system, for example), it is desirable to
bring the motor to a stop faster than can be achieved
through controlling via ramp down or by free-wheeling. In
such applications, use dynamic braking with a brake
resistor to ensure that the energy is absorbed in the
resistor and not in the frequency converter.
If the amount of kinetic energy transferred to the resistor
in each braking period is not known, calculate the average
power on the basis of the cycle time and braking time
(intermittent duty cycle). The resistor intermittent duty
cycle is an indication of the duty cycle at which the
resistor is active. Illustration 2.33 shows a typical braking
cycle.
The intermittent duty cycle for the resistor is calculated as
follows:
Duty Cycle = t
b
/ T
T = cycle time in seconds
t
b
is the braking time in seconds (as part of the total cycle
time)
Introduction VLT® HVAC Drive FC 102 Design Guide
MG16C102 - Rev. 2013-08-20 45
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