Baldor MicroFlex e100 - Resistor Choice; Resistor Derating

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3-26 Basic Installation MN1942
3.7.4 Resistor choice
P
av
is the value to use when assessing which regeneration resistor to use. However, a safety
margin of 1.25 times is recommended to ensure the resistor operates well within its limits*, so:
Required resistor power rating = 1.25 × P
av
= ________________ W (watts)
The range of suitable regeneration resistors is shown in Table 6. Choose the resistor that has a
power rating equal to or greater than the value calculated above.
Baldor catalog number
Resistance Power rating
RGJ139 39 Ω 100 W
RGJ160 60 Ω 100 W
RGJ260 60 Ω 200 W
RGJ360 60 Ω 300 W
Table 6 - Regeneration resistors
Dimensions are shown in section A.1.5.
* The regeneration resistors listed in Table 6 can withstand a brief overload of 10 times the rated
power for 5 seconds. Please contact Baldor if larger power ratings are required.
3.7.5 Resistor derating
The regeneration resistors shown in Table 6 can achieve their stated power rating only when
mounted on a heatsink. In free air a derating must be applied. Furthermore, in ambient
temperatures greater than 25 °C (77 °F), a temperature derating must be applied.
Resistor
(Baldor
part)
Nominal
power
rating
(W)
In free air On heatsink
RGJ139
RGJ160
100
Derate power linearly from:
80% @ 25 °C (77 °F)
to
70%@55°C(113°F)
Derate power linearly from:
100% @ 25 °C (77 °F)
to
88%@55°C(113°F)
Typical heatsink:
200 mm x 200 mm x 3 mm
RGJ260 200
Derate power linearly from:
70% @ 25 °C (77 °F)
to
6
2
%
@
5
5
°
C
(
1
1
3
°
F
)
Derate power linearly from:
100% @ 25 °C (77 °F)
to
8
8
%
@
5
5
°
C
(
1
1
3
°
F
)
RGJ360 300
6
2
%
@
5
5
°
C
(
1
1
3
°
F
)
8
8
%
@
5
5
°
C
(
1
1
3
°
F
)
Typical heatsink:
400 mm x 400 mm x 3 mm
Table 7 - Regeneration resistor derating