Machine Protection
6-35
Motor Overheating Protection Using PTC Thermistor Inputs
This function provides a motor overheating protection using a thermistor (PTC characteristic – Positive Tem-
perature Coefficient) that is built into the windings of each motor phase.
Related Constants
PTC Thermistor Characteristics
The following diagram shows the characteristics of the PTC thermistor temperature to the resistance value.
Fig 6.25 PTC Thermistor Temperature-Resistance Value Characteristics*
* The shown resistance value is for one motor phase. Normally the resistors are connected in series.
Con-
stant
Number
Name Description
Setting
Range
Factory
Setting
Change
during
Opera-
tion
Access
Level
L1-03
Alarm operation selection during
motor overheating
Selects the operation when the input motor temperature
(thermistor) input exceeds the alarm detection level (1.17
V).
0: Decelerate to stop
1: Coast to stop
2: Emergency stop using the deceleration time in C1-09.
3: Continue operation (oH3 on the Digital Operator
flashes).
0 to 3 3 No A
L1-04
Motor overheating operation
selection
Selects the operation when the motor temperature (ther-
mistor) input exceeds the operation detection level (2.34
V).
0: Decelerate to stop
1: Coast to stop
2: Emergency stop using the deceleration time in C1-09.
0 to 2 1 No A
L1-05
Motor temperature input filter
time constant
Sets the delay time constant for the motor temperature
(thermistor) input in seconds.
0.00 to
10.00
0.20 s No A
Resistance (Ohms)
Class F
Class H
Tr: Temperature threshold value
Temperatue
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