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72
Unidrive SPM User Guide
www.controltechniques.com Issue Number: 3
Table 6-11 Available resistors
If it is difficult to find a suitable resistor then a resistor with a higher P x R
product may have to be used.
The P x R product of the resistor should be larger than:
Table 6-12 Allowable Softstart resistor range
For multiple modules, divide the resistance by the number of modules.
For example the minimum resistance for 3 x SPMD1404 is 6.7
Ω.
Figure 6-10 Example of resistor overload characteristic
Circuit Breaker
Protection for the softstart circuit must be provided. The recommended
protection is to use a miniature circuit breaker (MCB) having a thermal
magnetic trip. The thermal part of the tripping mechanism protects
against a high impedance short circuit and the magnetic part of the trip
protects the resistor against a direct short circuit.
Many different MCBs are possible, e.g.:
•
GB2CB range from Telemecanique
•
S 281-K range from ABB
Table 6-13 MCBs available from Control Techniques
Figure 6-11 Example of tripping characteristic
Resistor
value
Ω
Power
rating
W
Energy
rating
J
CT part
number
P x R
product
V
2
150
53
170
1270-3157
7950
48
148
1,700
1270-2483
7104
CT part number
Min. Resistance
Ω
Max. Resistance
Ω
SPMA14X1
SPMD14X1
30
300
SPMD12X1
SPMA14X2
SPMD14X2
24
240
SPMA16X1
SPMA16X2
SPMD16X1
SPMD16X2
105
1051
SPMD12X2
SPMD14X3
SPMD14X4
20
200
SPMD16X3
SPMD16X4
79
789
SPMD12X3
SPMD12X4
17
168
P R
×
V
ll
2
10.9
-----------
=
10
1
0 1 2
5
10
Duration of Load (seconds)
%
Mu
ltipl
es
of r
ate
d P
o
w
er
100
20
25
50 100
CT part
number
Rated current
Rated voltage
No of poles
4133-0117
0.3
480
1
4133-0217
1
480
1
4133-0277
2
480
1
0.01
0.02
0.04
0.06
0.1
0.2
0.4
0.6
1
2
4
6
10
20
40
1
2
4
6
10
20
40
60
120
1.5
2
3
4
1
5
6
8 10
15
20
30
14
21
10
T
ripping
tim
e
Seconds
Minutes
Multiple of rated current
Thermal Trip
Area
Hot
Cold
Magnetic Trip
Area