Overcurrent/overvoltage protection

If a short-circuit or other problem on the load side causes an excessive current flow or generates abnormal voltage, the overcurrent/ overvoltage protection systems automatically cut off the output voltage to protect the power-supply circuit.

If the overcurrent or overvoltage protection system are activated and the power-supply circuit does not generate DC voltage, it is necessary to turn the power off, correct the problem, and then turn the printer on again.

The circuit has two fuses (FU1, FU2), which break and cut off the output voltage if overcurrent flows through the AC line.

Fuser over-temperature protection

The fusing-heater safety circuit is located on the engine controller board

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and constantly monitors the fusing temperature.

To protect the fuser from excessive temperatures, the printer has the following three protective functions:

•The CPU monitors the voltage of the FSRTH1 and FSRTH2 thermistor signals. If the fuser temperature reaches 240° C (464° F), then the CPU turns off the relay (RL101) to interrupt the power to the fusing heater.

•If the temperature of the fusing heater continues to rise abnormally, and the temperature of the thermal switch (TP101) exceeds about 250° C (482° F), TP101 opens up to cut off the power supply to the fusing heater.

•The power supply on the coil side of RL101 and RL102 is connected to +24 VB. When the top cover is opened, the power supply to RL101 and RL102 is cut off, and the relay is turned off.

EN

AC and DC power distribution 139