Danfoss VLT HVAC, Design Manual, Page: 49 / 200

Using a digital input and 24 V as power supply:
Example: The frequency converter trips when the motor temperature is
too high.
Parameter set-up:
Set par. 1-90
Motor Thermal Protection to Thermistor Trip [2]
Set par. 1-93 Thermistor Source to Digital Input 33 [6]
Using a digital input and 10 V as power supply:
Example: The frequency converter trips when the motor temperature is
too high.
Parameter set-up:
Set par. 1-90
Motor Thermal Protection
to
Thermistor Trip
[2]
Set par. 1-93
Thermistor Source
to
Digital Input 33
[6]
Using an analog input and 10 V as power supply:
Example: The frequency converter trips when the motor temperature is
too high.
Parameter set-up:
Set par. 1-90
Motor Thermal Protection
to
Thermistor Trip
[2]
Set par. 1-93 Thermistor Source to Analog Input 54 [2]
Do not select a reference source.
Input
Digital/analog
Supply Voltage
Volt
Threshold
Cut-out Values
Digital 24 V < 6.6 k Ω - > 10.8 k Ω
Digital 10 V < 800 Ω - > 2.7 k Ω
Analog 10 V < 3.0 k Ω - > 3.0 k Ω
NB!
Check that the chosen supply voltage follows the specification of the used thermistor element.
Summary
With the Torque limit feature the motor is protected for being overloaded independent of the speed. With the ETR the motor is protected for being over
heated and there is no need for any further motor protection. That means when the motor is heated up the ETR timer controls for how long time the
motor can be running at the high temperature before it is stopped in order to prevent over heating. If the motor is overloaded without reaching the
temperature where the ETR shuts of the motor, the torque limit is protecting the motor and application for being overloaded.
ETR is activated in par. and is controlled in par. 4-16 Torque Limit Motor Mode . The time before the torque limit warning trips the frequency converter
is set in par. 14-25 Trip Delay at Torque Limit .
VLT ® HVAC Drive Design Guide 2 Introduction to VLT HVAC Drive
MG.11.B9.02 - VLT
®
is a registered Danfoss trademark
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