System Manual – MOVITRAC® 07
93
5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Selection of the braking resistor
Project Planning
5.8
Selection of the braking resistor
•
Parallel connection
Two braking resistors must be connected in parallel in the case of some inverter/re-
sistor combinations. In this case, the trip current must be set on the bimetallic relay
to twice the value of I
F
entered in the table.
•
Peak braking power
The DC link voltage and the resistance value mean the peak braking power may be
less than the load capacity of the braking resistor. The formula for calculating the
peak braking power is:
P
max
= V
DC
2
/R
V
DC
is the switch-in threshold of the brake chopper. Its value is
•
With 400/500 V units: 822 V
DC
•
With 230 V units: 480 V
DC
The following table lists the peak braking power levels which are possible for the dif-
ferent resistance values.
Power diagrams
You can calculate the continuous resistor dissipation during braking procedures within
the cycle duration T. The default value for T is 120 s. Calculate the continuous resistor
dissipation with the cdf braking power and the following power diagrams. The right-hand
axis displays the continuous resistor dissipation (100 % cdf power).
•
High voltage
The connection leads to the braking resistor carry a high DC voltage (ca. 900 V).
Select the braking resistor cables with regard to this high DC voltage.
•
Cable length
The maximum permitted line length between MOVITRAC
®
07 and the braking resis-
tor is 100 m (330 ft).
Resistance [
Ω]
Peak braking power [kW]
400/500 V units
230 V units
100
6.7
–
72
9.4
3.2
68
10.0
–
47
14.4
–
39
17.3
–
27
25
8.5
18
37.5
–
15
45
–
12
56
19.2
9 (2 x 18
Ω
parallel)
–
25.6
