KYORITSU 5406A - Manual (Page 11)

― 9 ―
5. Residual Current Device (RCD) Test
5.1 RCD test
RCD is a switching device designed for breaking currents (opening the
contacts) when the residual current attains a specific given value. It works on
basis of current difference between phase currents flowing to different loads
and returning current flowing through neutral conductor (for a single phase
installation).
In case the current difference is higher than RCD tripping current, the device
will trip disconnecting the main voltage.
Fig. 5
Basically there are two classifications for RCD's : The first one due to the
shape of residual current waveform sensibility (Type AC and A) and the
second due to the tripping time (Type G and S).
● RCD type AC, RCD for which tripping is ensured for residual sinusoidal
alternating currents, whether suddenly applied or slowly rising. This type
is the most frequently used on electrical installations.
● RCD type A, RCD for which tripping is ensured for residual sinusoidal
alternating currents (like type AC) and residual pulsating direct currents
(DC), whether suddenly applied or slowly rising. It is not very used in
practice even if it is becoming more and more popular and in some
countries it is requested by the national regulation instead of type AC.
● RCD type G = General type (without trip out time-delay), for general use
and application.
OUTPUT
L
N
N
L
INPUT