Danfoss VLT AQUA Drive FC 202 Design Manual page 40

Introduction
nominal speed at twice the nominal speed and at 0.2x the
nominal speed.
2 2
It is clear that at lower speed the ETR cuts off at lower
heat due to less cooling of the motor. In that way, the
motor is protected from being over heated even at low
speed. The ETR feature is calculating the motor
temperature based on actual current and speed. The
calculated temperature is visible as a read out parameter
in 16-18 Motor Thermal in the frequency converter.
The thermistor cut-out value is > 3kΩ.
Integrate a thermistor (PTC sensor) in the motor for
winding protection.
Motor protection can be implemented using a range of
techniques: PTC sensor in motor windings; mechanical
thermal switch (Klixon type); or Electronic Thermal Relay
(ETR).
R
(Ω)
4000
3000
1330
550
250
-20°C
Illustration 2.27 Trip
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 1-90 Motor Thermal Protection to [2] Thermistor Trip
Set 1-93 Thermistor Source to [6] Digital Input 33
38
®
VLT AQUA Drive FC 202 Design Guide
 [°C]
 nominel -5°C
 nominel +5°C
 nominel
®
MG20Z102 - VLT
12 13 18 19 27 29 32 33 20
PTC / Thermistor
Illustration 2.28 Digital Input and 24 V Power Supply
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 1-90 Motor Thermal Protection to [2] Thermistor Trip
Set 1-93 Thermistor Source to [6] Digital Input 33
39 42 50 53 54 55
12 13 18 19 27 29 32 33 20
PTC / Thermistor
Illustration 2.29 Digital Input and 10 V Power Supply
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 1-90 Motor Thermal Protection to [2] Thermistor Trip
Set 1-93 Thermistor Source to [2] Analog Input 54
Do not select a reference source.
39 42 50 53 54 55
PTC / Thermistor
Illustration 2.30 Analog Input 10 V Power Supply
is a registered Danfoss trademark
OFF
37
ON
<6.6 k Ω >10.8 k Ω
OFF
37
ON
<800 Ω >2.7 kΩ
OFF
ON
<3.0 k Ω
>3.0 k Ω
R
R
R