8
Power De-rating
The RCB1200 power supply must always be operated within its stated operating limits. Equipment manufacturers and other
users must take appropriate de-ratings into account at all times when specifying a unit for the intended application. If in
doubt, contact your sales representative or Roal Electronics for assistance.
There are two main de-ratings for the RCB1200 power supplies, environment temperature and input line voltage. Temperature
de-ratings apply to both input and output stages, while line de-ratings apply only to the input stages.
For temperature, the de-rating for both input and output stages is 2.5% (of maximum rated power) per degree Celsius above
50 °C. While, for input line voltage, the de-rating for the input stages only is 0.83% (of maximum rated power) per Volt below
120 V
RMS
. These de-ratings can be calculated
using the following conditional equations;
Equation for line de-rating:
If V
in
< 120 V
RMS
,
P
out
= P
rated
* Line de-rating factor
= P
rated
* (1- (0.0083 * (120 - V
in
))
Otherwise,
P
out
= P
rated
Equation for temperature de-rating:
If temp > 50 °C,
P
out
= P
rated
* Temp de-rating factor
= P
rated
* (1 - (Temp - 50) * 0.025)
Otherwise,
P
out
= P
rated
Depending on the application conditions, one or both of the de-ratings may apply. Where both apply, the de-rating factors
given above can be multiplied together to obtain the total derating factor.
Example:
What are the RCB1200 input and output module de-ratings at 60 °C at 100 V
RMS
line?
Input power rating
=
P
rated
* Line de-rating factor * Temp de-rating factor
Output power rating
=
P
rated
* Temp de-rating factor
Line derating factor
=
(1-(0.0083*(120-V
in
))
=
(1-(0.0083*(120-100))
=
0.83
Temperature de-rating factor =
(1-(Temp-50)*0.025)
=
(1-(60-50)*0.025)
=
0.75
Input power rating
=
1200*0.83*0.75
=
747 W =
373.5 W available in each section.
Output B/C/D power rating =
150*0.75
=
112.5 W
Output A power rating =
125*0.75
=
93.75 W
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