Specifications

the ETR cuts off and trips the frequency converter. The
curves are showing the characteristic nominal speed at
twice the nominal speed and at 0.2x the nominal speed.
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 are protected from being over heated even at low
speed. The ETR feature is calculating the motor
temperature based on actual current and speed.
The thermistor cut-out value is >3 kΩ.
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).
1330
550
250
-20°C
175HA183.10
4000
3000
R
(Ω)
 nominel
 nominel -5°C
 nominel +5°C
 [°C]
Illustration 2.28 Trip due to High Motor Temperature
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 29
R
OFF
ON
<800 Ω >2.9 kΩ
18
19
12 20 55
27 29 42 45 50 53 54
DIGI IN DIGI IN DIGI IN DIGI IN
61 68 69
N P COMM. GND
+24V
0/4-20mA A OUT / DIG OUT 0/4-20mA A OUT / DIG OUT
COM A IN
COM DIG IN
10V/20mA IN 10V/20mA IN 10V OUT
BUS TER.
OFF ON
130BB898.10
Illustration 2.29 Digital Input/10 V Power Supply
Product Overview
VLT
®
HVAC Basic Drive FC 101 Design Guide
MG18C502 - Rev. 2013-09-06 39
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