Danfoss VLT HVAC Basic Drive FC 100 Series Design Manual page 37

Introduction to VLT HVAC Ba...
Motor protection can be implemented using a range of
techniques: PTC sensor in motor windings; mechanical
thermal switch (Klixon type); or Electronic Thermal Relay
2 2
(ETR).
R
(Ω)
4000
3000
1330
550
250
-20°C
Using a digital input and 10V as power supply:
Example: The frequency converter trips when the motor
temperature is too high.
Parameter set-up:
Set 1-90 Motor Thermal Protection to Thermistor Trip [2]
Set 1-93 Thermistor Source to Digital Input 29 [6]
BUS TER.
OFF ON
61 68 69
0/4-20mA A OUT / DIG OUT
36
VLT HVAC Basic Drive Design Guide
 nominel -5°C
 nominel +5°C
 nominel
18 19 27 29 42 45 50 53 54
0/4-20mA A OUT / DIG OUT
12 20 55
OFF
ON
R
<800 Ω >2.9 kΩ
MG.18.C2.02 - VLT
Using an analog input and 10V as power supply:
Example: The frequency converter trips when the motor
temperature is too high.
Parameter set-up:
Set 1-90 Motor Thermal Protection to Thermistor Trip [2]
Set 1-93 Thermistor Source to Analog Input 54 [2]
NOTE
Do not set Analog Input 54 as reference source.
BUS TER.
OFF
61 68 69
 [°C]
Input
Digital/analog
Digital
Analog
NOTE
Check that the chosen supply voltage follows the specifi-
cation of the used thermistor element.
COM A IN
COM DIG IN
Summary
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.
ETR is activated in 1-90 Motor Thermal Protection.
®
is a registered Danfoss trademark
ON
18 19 27 29 42 45 50 53 54
0/4-20mA A OUT / DIG OUT 0/4-20mA A OUT / DIG OUT
12 20 55
OFF
ON
<3.0 k Ω
>2.9k Ω
Supply Voltage Threshold
Volt Cut-out Values
10V < 800Ω - > 2.9kΩ
10V
< 800Ω - > 2.9kΩ
COM A IN
COM DIG IN
R