HP Enterprise 500 manual Fuser over temperature protection

Fuser over temperature protection

To protect the fuser from excessive temperatures, the product has four layers of protective functions. If one function fails, the subsequent functions should detect the problem.

●DC controller: When a thermistor or thermopile detects a temperature above a certain threshold, the DC controller interrupts power to the specific heater. Following are the thresholds for each component:

◦TH1: 230° C (446° F) or higher

◦TH2: 285° C (545° F) or higher

◦TH3: 285° C (545° F) or higher

●Fuser heater safety circuit: If the DC controller fails to interrupt the power to the heaters at the prescribed temperatures, the fuser heater safety circuit deactivates the triac-drive circuit and releases the relay, which causes the heaters to stop at slightly higher temperature thresholds.

◦TH2: 290° C (554° F) or higher

◦TH3: 290° C (554° F) or higher

●Current detection protection circuit: If current flowing in each triac exceeds a specific value, the current detection protection circuit deactivates the triac-drive circuit and releases the relay, which interrupts the power supply to the heaters.

●Thermoswitch: If the temperature in the heaters is abnormally high, and the temperature in the thermoswitches exceeds a specified value, the contact to the thermoswitch breaks. Breaking this contact deactivates the triac-drive circuit and releases the relay, which interrupts the power supply to the heaters. Following are the thresholds for each thermoswitch:

◦TP1: 270° C (518° F) or higher

NOTE: When the thermoswitches reach this temperature, the temperature on the fuser rollers is about 320° C (608° F).

ENWW Engine control system 17