MV3DB Series DB Units
3. System Design
(07/06)
ALSPA MV3000e Dynamic Braking Units
Page 3-5
0
0.2
0.4
0.6
0.8
1
1.2
0
20
40
60
80
100
120
140
160
180
200
Duration of braking, t1 (seconds)
Derat
ing fact
or per unit
(p.u.)
Figure 3-3 Derating factor
3.6.2
For braking times less than 18 seconds:
•
the peak power given in the Specification section must not be exceeded;
•
the total cycle time
t
3
can be reduced but the long term average power must not exceed
10% of the “Nominal Power during 18 seconds ON time” given
in Table 2-1.
3.7 Braking
Resistor Cable Selection
The cables must conform to local wiring regulations. Cables rated less than the peak current
rating of the DB Unit in Table 2-1 should not be used unless they are protected against
overload by means external to the drive.
The maximum sizes of cable which can be connected to the optional dynamic braking resistors
are shown in Table 3-1.
Temperature Limitations
1.
Cables connected to the resistor terminals inside the resistor casing must be capable of
withstanding a local air temperature up to 80 ˚C (176 ˚F). The conductor temperature at
this end of the cable must not be allowed to exceed 160 ˚C (320 ˚F).
2.
Cables connected to the drive terminals must be capable of withstanding a temperature
of 70 ˚C (158 ˚F), (60 ˚C (158 ˚F) on drives rated at less than 100 A mains or motor
current). The conductor temperature must not be allowed to exceed 120 ˚C (248 ˚F).
