SuperSigma2 AM PMS
–
V1.5.6 17-1-2020
Page 77 (97)
©2019 DMC GmbH Herten Germany
Example
•
Nominal rated current
90 A
•
Insulation class
F
•
Rise time
50 s
Thus, the motor heats up 105 °C in 50 s when 180 A is drawn, the providing starting temperature is 40 °C.
Parameters
The controller will have a set of parameters with which the I
2
t feature can be set up:
•
Nominal rated current of the motor.
•
The temperature rise time.
•
Percentage of the maximum drive current 1.
•
Percentage of the maximum drive current 2.
•
Percentage of the maximum drive current 3.
The location, unit, range and step size of these adjustments can be found in the “Menu 7 “Limits Setup””
.
This rise time must be established by trial and error. Once this time is established, it sets a time in which the surplus of
the nominal current may flow through the motor. After that time, the I
2
t function will limit the motor current in three
steps.
There is Microsoft Excel sheet (available on request) which can be used to setup the I
2
t parameters in the
of the Sigma2 controller. In this sheet various current settings and the time can be filled in the white boxes (see
also the example below). The figures in bold in the dark green box are the actual current limit value in percentages. These
need to be configured in the
of the controller.
A limit will run from 100 %
(no cut back) to 0 % (full cut back). This is displayed also in the “Status Menu” at “Drive torque
limit”.
When the I
2
t feature is actually limiting the current, the “Status menu” will show ‘T1’, ‘T2’ or ‘T3’ limit indication,
depending in which phase the I
2
t function currently is.
The reason that percentages are used instead of real currents, is that all other limit features such as low voltage limit and controller temperature
limit are also in percentages.
Note
that the maximum current is specified by the maximum RMS current in the Motor Autotune menu (
Example
An example of the MS Excel sheet is given below.
According to the sheet, 400 Arms is allowed to flow through the motor for a maximum time of 20 s. After that the I
2
t will
cut back the current to the first step (63 %, 250 Arms).
Motor Setup Menu
Maximum Torque current in drive
ImotMax
400 Arms
Nominal motor current
NomCurr
100 Arms
100
Arms
I
2
t Time
I2TTime
180 sec
180
sec
I
2
t Cut Back Current 1
I2TCutB1
250 Arms
63%
%
I
2
t Cut Back Current 2
I2TCutB2
160 Arms
40%
%
I
2
t Cut Back Current 3
I2TCutB3
120 Arms
30%
%
I
2
x t
1800000 A^2s
Step
0
T1
T2
T3
I_max [A]
400
250
160
120
I_offset [A]
300
150
60
20
t [s]
20,00
80,00
500,00
4500,00
t [min]
0,33
1,33
8,33
75,00
t [h]
0,01
0,02
0,14
1,25
Menu Motor Limits
Setting up I2t parameters
To use in Motor Limits Menu
