Danfoss VLT 2800 Design Manual page 75

Programming
•
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
rated motor frequency f
into account the need for lower loading at low
speeds due to the motor's internal ventilation
being reduced.
t [s]
2000
1000
600
500
400
300
200
100
60
50
40
30
20
10
1.0 1.2 1.4 1.6 1.8
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.
MG27E402
Design Guide
and
M,N
. The calculations take
M,N
f OUT = 1 x f M,N (par. 1-23)
f OUT = 2 x f M,N
f OUT = 0. 2 x f M,N
I
M
I (par. 1-24)
2.0
MN
Danfoss A/S © Rev. May/2014 All rights reserved.
130 Start frequency
Value:
0.0 - 10.0 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
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
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.
0.0 Hz
4 4
0.0 V
0%
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