Sagem 4450E - Manual (Page 152)

CHAPTER 10
3P@C Installation Manual
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10. Power Distribution System
Maintenance
10.1. Checking Air-break Switch
The air-break switch is in the DC power distribution panel, with the overcurrent protection and short circuit
protection functions. In the normal running process, the air-break switch is ON. When a large current passes
through the air-break switch, the air-break switch switches from ON to OFF to cut off the power supply, so the
device is protected.
Usually, you do not need to check the air-break switch. When the air-break switch switches to OFF suddenly, it
indicates that there is something wrong with the power distribution system of the device or the device, and you
should carefully look for the reasons that cause the short circuit protection before switching the air-break switch
to ON.
To find the reasons, you should cut off the power supply of the device firstly, switch the air-break switch to ON,
and use the multimeter to measure the input resistance. If the value of the resistance approximates to zero
Ω , it
indicates that there is the short circuit in the interior, and you need to locate each module. When plugging each
module, you can find the short circuit module by judging the change of the resistance before and after the
plugging, and you can switch the air-break switch to ON after the troubleshooting.