Testing Method Of Overcurrent Trip - Mitsubishi Electric NF250-SEV Instruction Manual

4.5 Testing method of overcurrent trip

Test by using the "Y-351" breaker tester (option) or by energizing the MDU Breaker main unit.
If using the "Y-351" breaker tester, follow the instructions in that product's Instruction Manual.
● For the pre-alarm contact output for MCCB (with alarm contact attached [optional]), the MDU is connected to the MDU Breaker main unit and
will not operate unless control power is applied to the MDU and the alarm contact output.
● The MDU measurement function, alarm function, accident cause and current display, and communication function cannot be confirmed if the
"Y-351" breaker tester is used.
This section describes how to test after energizing the MDU Breaker main unit.
1 250 A frame
(1) Send AC power to the MDU Breaker main unit from a 3-phase power supply or 1-phase power supply.
When using a 1-phase power supply, do so from two poles in series.
Current adjustable resister
(2) Each operating current can be confirmed by checking the LEDs on the front of the MDU Breaker main unit.
70% LED (green): Acceptable when it begins to stay ON within 60% to 80% of current setting (lr).
OVER LED (red) : Acceptable when it begins to stay ON within 105% to 125% of current setting (lr).
* MDU breaker with PAL/EPAL module (option)
Pre-alarm operation display LED: Acceptable when it starts to blink within 90% to 110% of current setting (Ir).
(3) The long time delay and pre-alarm operating times can be confirmed by sending a current equivalent to 200% of current setting (lr).
However, if a current exceeding current setting (lr) is sent prior to this test, the operating time will shorten and the first measurement will be invalid.
Tripping the MDU Breaker main unit will reset the tripping circuit, allowing the following operating time to be measured correctly.
The pre-alarm operating time is half of the long time delay operating time (TL).
200% current
OVER LED (red)
* MDU breaker with PAL/EPAL module (option)
Pre-alarm operation display LED
Acceptable if measured operating time is within range below.
Measurement item
Pre-alarm operating time
Long time delay operating time
Caution
Current adjustable resister
With lp = 0.7 × lr, acceptable when it starts to blink within 60% to 80% of current setting (lr).
Long time delay operating time
Pre-alarm output
Pre-alarm
operating time
TL = 12 s TL = 60 s
4.8 to 7.2 s 24 to 36 s
9.6 to 14.4 s 48 to 72 s
Trip
TL = 80 s
32 to 48 s
64 to 96 s
8
TL = 100 s
40 to 60 s
80 to 120 s