Technical information
RCD
for EC fans
www.guentner.de
Technical information - RCD for EC fans V_3.0
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Contents
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RCD for EC fans V_3.0................................................................ 3
1.1
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Technical information - RCD for EC fans V_3.0
© Güntner GmbH & Co. KG
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1
RCD for EC fans V_3.0
1.1
RCD – recommendations
RCDs can be used for the detection / avoidance of fault currents in conjunction with EC motors. Different conditions must be noted however in relation to the design of the circuit breakers:
Note:
This information is simply a recommendation. The relevant expert or system designer locally is responsible for selecting the appropriate RCDs as they are the only ones who are familiar
with the construction and other components of the system and the legal constraints.
This is particularly important in relation to selectivity if several RCDs are to be cascaded.
No universally applicable statements can also be made with respect to requirements for fire
safety or additional protection (especially triggering thresholds). The entire system always has
to be considered in this case in order to make a statement.
There are essentially two types of RCD available, each with different triggering characteristics:
Type A: Current-sensitive residual current devices
Type A are current sensitive residual current devices, which are designed for detecting a/c
fault currents. These circuit breakers are the type usually used in households. They are not
suitable for use in conjunction with power electronics, such as frequency converters, phase
angle controls and EC fans.
With such power electronics, the direct voltage component may be substantial in the case of
faults and CANNOT be detected by Type A circuit breakers. Dangerous conditions could therefore arise despite the use of an RCD.
Type B and B+: AC/DC-sensitive residual current devices
Type B or B+ RCDs are absolutely essential for applications with power electronics such as
frequency converters and EC fans.
These circuit breakers are sensitive to universal current, which means that a/c or d/c fault
currents as well as a combination of both will definitely be detected.
B+ is a circuit breaker intended especially for high-frequency leakage currents in the range up
to about 20 kHz, but is not required for EC motors with integrated electronics.
Superresistant trigger behaviour "K"
RCDs that are described as superresistant are available for avoiding premature and thus unintentional triggering. The letter "K" (framed) is the usual abbreviation used for these circuit
breakers. The pulse suppression time with these RCDs is in the range of a few milliseconds.
These variants are available as Type A and as Type B or B+.
This superresistant behaviour is necessary with EC fans because the EC motors have Y capacitors integrated for suppressing interference (emitted interference). These capacitors are
loaded when the mains voltage is switched on and the resulting pulse currents can reach the
two-digit ampere range depending on the phase position at the cut-in time. These inrush current pulses are very short but can nevertheless trigger typical RCDs found in households. This
is why these superresistant RCDs have to be used.
Technical information - RCD for EC fans V_3.0
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Examples of "Siemens RCDs":
Recommended for EC fans:
Type B: 1-phase RCD
300mA,
300mA,
300mA,
300mA,
K,
K,
K,
K,
1+N,
1+N,
1+N,
1+N,
400V,
400V,
400V,
400V,
16A
25A
40A
63A
e.g.
e.g.
e.g.
e.g.
from
from
from
from
Siemens
Siemens
Siemens
Siemens
under
under
under
under
25A
40A
63A
80A
e.g.
e.g.
e.g.
e.g.
from
from
from
from
Siemens
Siemens
Siemens
Siemens
5SM3642-4
under 5SM3644-4
under 5SM3646-4
under 5SM3647-4
5SM3621-4
5SM3622-4
5SM3624-4
5SM3626-4
Type B: 3-phase RCD
300mA,
300mA,
300mA,
300mA,
K,
K,
K,
K,
3+N,
3+N,
3+N,
3+N,
400V,
400V,
400V,
400V,
Not recommended:
Type A: 3-phase RCD
30mA, K, 3+N, 400V, 40A
e.g. from Siemens under 5SM3344-6KK01
Overview of selection of RCDs:
RCCB:
Only RCDs without miniature circuit breakers
(Residual Current operated Circuit-Breaker without over current protection)
RCBO:
Combination of RCD and miniature circuit breaker
(Residual current operated Circuit-Breaker with Overcurrent protection)
SIGRES:
Protective devices for use under difficult environmental conditions
(e.g. chemical industry)
K:
Superresistent
Short-time delayed tripping in the case of transient leakage currents. High surge
current resistance: > 3 kA.
S:
Selective
Can be used as an upstream group impulse switch for selective tripping with respect to downstream, instantaneous or superresistant RCDs.
Technical information - RCD for EC fans V_3.0
© Güntner GmbH & Co. KG
Page 5 / 5
Technical information - RCD for EC fans V_3.0
© Güntner GmbH & Co. KG