9-58
The temperature at which the overheating
protection is to be activated depends on
the characteristics of the PTC thermistor.
As shown at the right, the internal
resistance of the thermistor will step up
near the alarm temperature detection
point. Determine the operation level
(voltage V
c1
) with reference based on the
variance in internal resistance.
Calculate the reference voltage Vc1 using the equation shown below and set it to function code
H27.
Substitute the internal resistance of the PTC thermistor at the alarm temperature with Rp to
obtain Vc
1:
(V)10×
Rp+250
Rp250
+R
Rp+250
Rp250
=Vc
1
1
x
x
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