User Guide

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
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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).
Fuser (fixing)-failure detection
When the DC controller detects any of the following conditions, it determines that the fuser has failed.
The DC controller then interrupts power to the fuser heaters and notifies the formatter.
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Abnormally high temperatures: Temperatures are too high for any of the following
components, at any time:
◦
TH1: 230° C (446° F) or higher
◦
TH2: 285° C (545° F) or higher
◦
TH3: 285° C (545° F) or higher
●
Abnormally low temperatures: Temperatures are too low at any of the following
components after the product has initialized.
◦
TH1: 120° C (248° F) or lower
◦
TP2 or TP3: 100° C (212° F) or lower
Or, the temperature drops in either of the thermopiles (TP2 and TP3) by 30° C (86° F) or more
within a specified length of time.
●
Abnormal temperature rise: The DC controller determines an abnormal temperature rise if
the detected temperature of TH1 does not rise 2° C within a specified time period after the fuser
(fixing) motor is turned on, or if the detected temperature of the thermistors does not rise to a
specified temperature for a specified time after the fuser (fixing) motor is turned on.
18 Chapter 1 Theory of operation ENWW