*
M’Ax Advanced User Guide
32
Issue Number: 4
www.controltechniques.com
The Motor overload warning bit 10.17 is set if integrator value is greater than Motor overload warning threshold 4.52. Also the output current
scaling is switched to parameter 4.53 (Current scaling during I
2
t limit).
When the I
2
t threshold goes above the limit set in parameter 4.52, the SLM alters its current scaling to limit the motor current in a default
state.
If a controller wants to use this as a warning bit, the threshold [4.52] can be adjusted to a required level (i.e. 75% instead of 110%). Changing
the I
2
t threshold in [4.52] will not limit the current scaling after the motor thermal overload alarm is set. In this case the controller should take
the necessary action to protect the motor, i.e. reduce acceleration or stop.
The drive will operate, when the motor thermal overload alarm is set, until the thermal overload time to trip parameter value [4.54] has been
exceeded.
Typical Example:
1.
Set 4.53 Symmetrical current limit after motor thermal-overload alarm at 200 (the largest of the symmetrical current limit values).
2.
Set 4.54 Thermal-overload time to trip at 12 (process cycle time, rounded-up to nearest integer).
3.
Calculate the following:
4.
Calculate the following:
5.
Calculate the following:
6.
Enter the calculated value into 4.52.
7.
Perform the following, as appropriate:
4.53
Symmetrical current limit after motor thermal-overload trip
ô
0 ~ 300
ð
105
%I
M
RW
Uni
Parameter
Value
4.15 Motor – thermal time-constant
89
4.07 Symmetrical current limit Kc1
150
4.24 Symmetrical current limit Kc2
200
4.28 Symmetrical current limit Kc3
175
Process cycle time
11.5s
Gain sequencing using all three PID-gains buffers
I2t trip threshold 4.52
Standard current Scaling
,
,
4.07 4.24 4.28
Current scaling
Current Scaling During I t Trip
2
4.53
I
2
t Warning threshold 4.56
0
1
0
1
SLM I t Trip Bit 13 Status
2
I t Warning Bit
Status
2
4.57
Accumulator value
10.58
Time
Time
t
c
4.15
[
]
–
In 1
2
105
2
4.53
[
]
-------------------
–
è
ø
ç
÷
æ
ö
×
=
t
c
89
–
In 1
2
105
2
200
------------
–
è
ø
ç
÷
æ
ö
×
28.7 s
( )
=
=
t
D
t
C
4.54
[
]
–
28.7
12
–
16.7 s
( )
=
=
=
4.52
[
]
4.53
[
]
1
e
t
–
D
4.15
[
]
⁄
–
×
=
4.52
[
]
200
[
]
1
e
16.7
–
(
)
89
⁄
–
×
82.7
=
=
(%)
Summary of Contents for M'Ax
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Page 47: ... M Ax Advanced User Guide 44 Issue Number 4 www controltechniques com ...
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Page 73: ... M Ax Advanced User Guide 70 Issue Number 4 www controltechniques com ...
