31
2
Operating characteristics and performance
2-6 Withstand voltage performance
Fig. 2-12 Test circuit for rated impulse withstand voltage
characteristics
Rs
L
Ro
Specimen
To the CRT
Impulse generator
Capacitor
Air gap
Fig. 2-13 Impulse voltage waveform
50μs
1.2μs
100
90
50
30
Voltage (%)
Fig. 2-14 Evaluating MCCBs by waveform observation
Not good
Good
2-6 Withstand voltage performance
2-6-1 Rated power frequency withstand voltage
(IEC 60947-1, 2)
(1) Circuit breaker body
The breaker should function normally with 2000V applied for
one minute at the following locations if it is rated at 300V or
less, and with 2500V applied for one minute at the following
locations if it is rated at more than 300V and 600V or less.
s "ETWEENTERMINALSONTHEPOWERSUPPLYSIDEANDTHELOAD
side with the breaker in the open or tripped state.
s "ETWEENOPPOSITEPOLARITYTERMINALSWITHTHEBREAKERCLOSED
(However, electronic components used for ground-fault
detection and overvoltage protection elements must be
electrically left open.)
s "ETWEENTHELIVEPARTANDGROUNDWITHTHEBREAKEROPENAND
closed.
(2) Breakers with non-electrically operated
accessories
(a) Between accessory circuits and the breaker live part
The breaker should withstand the following voltages above the
rated voltage applied to the control circuit for one minute.
60V or less: 1000V
More than 60V, but less than 600V:
(Rated voltage) u 2 + 1000V (1500V min.)
(b) Between accessory circuits and ground
The breaker should withstand (the rated voltage of the
accessory u 2 + 1000V) applied for one minute. The 1000V
are between contacts on the auxiliary switch.
(3) Electrically operated breakers
(a) Between electrically operated circuits and the live part
of the breaker
The breaker should withstand (the rated voltage of the breaker
u 2 + 1,000V) applied for one minute.
(b) Between electrically operated circuits and ground
The breaker should withstand (the rated voltage of the
electrically operated device u 2 + 1000V) applied for one
minute. The 1000V are on the operating motor.
2-6-2 Rated impulse withstand voltage
(IEC 60947-1, 2)
Use the test circuit shown in Fig. 2-12 in order to check rated
impulse withstand voltage performance. Apply the 1.2 u 50μs
voltage waveform shown in Fig. 2-13 between the live part
of the specimen and metal plate. Observe the waveform by
memory scope to determine whether the MCCB passes or not.
(See Fig. 2-14.)
Conduct the test on a new specimen. Use one that came with
the accessory, such as an auxiliary switch (W), alarm switch
(K), shunt trip device (F) or undervoltage trip device (R).
Fig. 2-14 shows the criteria for the test.
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