•
Via a PTC thermistor that is mounted on the
motor. The thermistor is connected between
terminal 50 (+10 V) and one of the digital input
terminals 18, 19, 27 or 29. See
parameter 300
Digital inputs
.
•
Thermal load calculation (ETR - Electronic Thermal
Relay), based on present load and time. This is
compared with the rated motor current I
M,N
and
rated motor frequency f
M,N
. The calculations take
into account the need for lower loading at low
speeds due to the motor's internal ventilation
being reduced.
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
MN
(par. 1-24)
I
M
Illustration 4.4 Thermal Load Calculation
ETR functions 1-4 do not begin to calculate the load until
the set-up in which they have been selected is activated.
This means that the ETR function can be used even when
changing between 2 or more motors.
Description of choice:
Select
[0] No protection
to disable a warning or trip when a
motor is overloaded.
Select
[1] Thermistor warning
to activate a warning when
the connected thermistor becomes too hot.
Select
[2] Thermistor trip
to activate a trip when the
connected thermistor becomes too hot.
Select
ETR warning 1-4
to enable a warning when the
motor is overloaded according to the calculations. It is
possible to programme the frequency converter to give a
warning signal via one of the digital outputs. Select
ETR
Trip 1-4
to activate a trip when the motor is overloaded
according to the calculations.
WARNING
This function cannot protect the individual motors in the
case of motors linked in parallel.
130
Start frequency
Value:
0.0 - 10.0 Hz
0.0 Hz
Function:
The start frequency is active for the time set in
parameter
120 Start delay
, after a start command. The output
frequency jumps to the next preset frequency. Certain
motors, such as conical anchor motors, need an extra
voltage/start frequency (boost) at start to disengage the
mechanical brake. To achieve this,
parameters 130 Start
frequency
and
131 Initial voltage
are used.
Description of choice:
Set the required start frequency. It is a precondition that
parameter 121 Start function
, is set to
[3] Start frequency/
voltage clockwise
or
[4] Start frequency voltage in reference
direction
and that a time is set and a reference signal is
present in
parameter 120 Start delay
.
NOTICE
If
parameter 123
is set higher than
parameter 130
, the
start delay function
(parameter 120 and 121)
is skipped.
131
Initial voltage
Value:
0.0 - 200.0 V
0.0 V
Function:
Initial voltage
is active for the time set in
parameter 120
Start delay
, after a start command. This parameter can be
used for example for lifting/dropping applications (conical
anchor motors).
Description of choice:
Set the required voltage necessary to cut out the
mechanical brake. It is assumed that
parameter 121 Start
function
, is set to
[3] Start frequency/voltage clockwise
or
[4]
Start frequency/voltage in reference direction
and that in
parameter 120 Start delay
a time is set, and that a reference
signal is present.
132
DC brake voltage
Value:
0 - 100% of max. DC brake voltage
0%
Function:
Use this parameter to set the DC brake voltage at which
the frequency converter brakes. This parameter is valid
when the DC brake cut-in frequency is reached, or when
DC braking inverse
is activated via a digital input or serial
communication. The DC brake cut-in frequency is set in
parameter 127 DC brake cut-in frequency
. The DC brake
voltage is active for the time set in
Parameter 126 DC brake
time
sets the duration during which the DC brake voltage
is active.
Programming
Design Guide
MG27E402
Danfoss A/S © Rev. May/2014 All rights reserved.
73
4
4
