3.3.9 1-9* Motor Temperature
1-90 Motor Thermal Protection
Option:
Function:
The frequency converter determines the
motor temperature for motor protection in
two different ways:
•
Via a thermistor sensor connected
to one of the analog or digital
inputs (
).
•
Via calculation (ETR = Electronic
Thermal Relay) of the thermal load,
based on the actual load and time.
The calculated thermal load is
comed with the rated motor
current I
M,N
and the rated motor
frequency f
M,N
. The calculations
estimate the need for a lower load
at lower speed due to less cooling
from the fan incorporated in the
motor.
[0]
*
No protection
If the motor is continuously overloaded and
no warning or trip of frequency converter is
wanted.
[1]
Thermistor
warning
Activates a warning when the connected
thermistor in the motor reacts in the event
of motor over-temperature.
[2]
Thermistor trip Stops (trips) the frequency converter when
the connected thermistor in the motor
reacts in the event of motor over-
temperature.
[3]
ETR warning 1
[4]
*
ETR trip 1
[5]
ETR warning 2
[6]
ETR trip 2
[7]
ETR warning 3
[8]
ETR trip 3
[9]
ETR warning 4
[10] ETR trip 4
ETR (Electronic Thermal Relay) functions 1-4 will calculate the
load when set-up where they were selected is active. For
example ETR-3 starts calculating when set-up 3 is selected.
For the North American market: The ETR functions provide
class 20 motor overload protection in accordance with NEC.
1.2
1.0
1.4
30
10
20
100
60
40
50
1.8
1.6
2.0
2000
500
200
400
300
1000
600
t [s]
175ZA052.12
fOUT = 2 x f M,N
fOUT = 0.2 x f M,N
fOUT = 1 x f M,N(par. 1-23)
I
M
,
N
(par. 1-24)
I
M
WARNING
In order to maintain PELV, all connections made to the
control terminals must be PELV, e.g. thermistor must be
reinforced/ double insulated
NOTE
Danfoss recommends using 24 VDC as thermistor supply
voltage.
1-91 Motor External Fan
Option: Function:
[0]
*
No No external fan is required, i.e. the motor is derated at
low speed.
[1]
Yes Applies an external motor fan (external ventilation), so
no derating of the motor is required at low speed. The
upper curve in graph above (fout = 1 x fM,N) is followed
if the motor current is lower than nominal motor current
(see
). If the motor current exceeds
nominal current, the operation time still decreases as if
no fan were installed.
Parameter Description
VLT
®
HVAC Drive Programming Guide
44
MG.11.CB.02 - VLT
®
is a registered Danfoss trademark
3
3
