Sigmatek FDD Sizes 7 to 9 Power Installation Guide
59
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P
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Table 4-6 Braking transistor turn on voltage
4.7.1
External braking resistor
When a braking resistor is to be mounted outside the enclosure, ensure that it is mounted in a
ventilated metal housing that will perform the following functions:
•
Prevent inadvertent contact with the resistor
•
Allow adequate ventilation for the resistor
When compliance with EMC emission standards is required, external connection requires the cable
to be armored or shielded, since it is not fully contained in a metal enclosure. See section
4.9.6
Compliance with generic emission standards
on page 72 for further details.
Internal connection does not require the cable to be armored or shielded.
Table 4-7 Minimum resistance values and peak power rating for the braking resistor at 40 °C (104 °F)
*Resistor tolerance: ±10 %.
The minimum resistance specified are for stand-alone drive systems only. If the drive is to be used as
part of a common DC bus system different values may be required. Contact the supplier of the drive
for more information.
For high-inertia loads or under continuous braking, the continuous power dissipated in the braking
resistor may be as high as the power rating of the drive. The total energy dissipated in the braking
resistor is dependent on the amount of energy to be extracted from the load.
The instantaneous power rating refers to the short-term maximum power dissipated during the on
intervals of the pulse width modulated braking control cycle. The braking resistor must be able to
withstand this dissipation for short intervals (milliseconds). Higher resistance values require
proportionately lower instantaneous power ratings.
In most applications, braking occurs only occasionally. This allows the continuous power rating of the
braking resistor to be much lower than the power rating of the drive. It is therefore essential that the
Drive voltage rating
DC bus voltage level
400 V
780 V
When a braking resistor is used, Pr
00.028
should be set to FASt ramp mode.
Overload protection
When an external braking resistor is used, it is essential that an overload protection device
is incorporated in the braking resistor circuit; this is described in
Model
Minimum resistance
*
Instantaneous power rating
Continuous power rating
Ω
kW
kW
400 V
074.00660
7.5
90.2
30
074.00770
7.5
90.2
37
074.01000
7.5
90.2
45
084.01340
6.3
107.4
55
084.01570
6.3
107.4
75
094.02000 (9A)
3.6
187.8
90
094.02240 (9A)
3.6
187.8
110
094.02000 (9E)
2.6
260
90
094.02240 (9E)
2.6
260
110
NOTE
WARNING
Summary of Contents for 074.00660
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