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USER'S MANUAL
SYSTEM MENU 5: THERMAL POWER FOLDBACK MODE
This menu option allows the user to turn Thermal Power
Limiting on or off (
Fig. 2.10
). On hot days, when the
LR-24 is putting out 200 watts or more, it may eventually
overheat and shutdown to prevent possible damage to the
electronics. Thermal Power Limiting allows the LR-24 to
better control the amount of internal heat being produced
and in many cases can prevent thermal shutdown. This
feature allows the LR-24 to continue to function in hot
environments where it would otherwise shut down. When
this option is turned on, the LR-24 will automatically
reduce its output frequency if one of the pulsed outputs
has been selected or it will reduce its output voltage
if Direct Current output has been selected. The LR-24
reduces the output by 20% for every 2 degrees Fahrenheit
above the trip point, up to a maximum of 80% reduction.
The LR-24 has two thermal sensors inside: one monitors
the air temperature inside the electronics cover and the
other monitors the temperature of the heat sink. The trip
points are 150 degrees for the air temperature and 190
degrees for the heat sink temperature. The shutdown
temperature for the air is 160 degrees and 200 degrees
for the heat sink. If either of the shut down temperatures
is reached, the LR-24 will shut down even if Thermal
Power Limiting is enabled. With Thermal Power Foldback
enabled when either of the trip points is reached, the
LR-24 will begin to beep both audio alarms simultaneously
and the status screen will look similar to that shown in
Figure 2.11
.
This display says that the LR-24 has entered thermal
power limiting. The output frequency has been reduced
by 20%. The output frequency was set to 60Hz and has
been reduced to 48Hz. The average output current is 1.62
amps and the peak output current is 5.83 amps. If the
temperature continues to rise, the LR-24 will continue to
reduce the output in 20% steps to a maximum of 80%.
This status display can be seen as long as the pole switch
is pressed. When the pole switch is released, the standard
status screen will return. This allows continued monitoring
of battery condition, or the temperature of the LR-24.
As the LR-24 cools down the output is automatically
increased back toward the original settings. The LR-24
will not increase the output beyond the original settings.
System Menu
5/9
Enable Thermal Power Foldback?
Fig. 2.10
Thermal Foldback
20% Time 8314S
Set 60Hz Now 48Hz
Output 1.62A 5.83Ap
Fig. 2.11
SECTION 2: DISPLAY PANEL (CONT.)
SECTION 2