Derating Curve; Calculating Flow Capacity Of The Fan - CD Automation REVEX 1PH User Manual

REVEX
1PH 280A

6.6 Derating Curve

The nominal current of the units in specification are referred to continuous service at 40°C ambient temperature.
For higher temperature multiply the nominal current times derating coefÏcient K below represented:
l max = l nominal x K
Derating
For higher cabinet
temperature
(more than 50°C)
contact the producer
of the unit

6.7 Calculating flow capacity of the fan

All the thyristor units when are in conduction produces power loss that is dissipated inside cubicle in terms of
heating. Due to this fact the internal temperature of cubicle is higher than ambient temperature. To be cooled
the thyristor need of fresh air cooling and to do it is normally used a fan mounted on the front door or on the
roof of the cabinet.
Procedure to size Fan air mass flow (V): see power loss or each thyristor and fuse mounted indicated in the
manual related to the current (Output feature and Internal fuse Chapter).
Qv = total power losses (w)
V=f * Qv
ta = ambient temperature (°C)
tc = cabinet temperature (°C)
tc-ta
V = fan air mass flow (m3/h)
f = altitude coefÏcient (see table on right)
The formulas used are for information only and is not a substitute for a proper thermal
rating done by a qualified person.
1,2
1
0,8
0,6
0,4
0,2
0
15
(thyristor + fuse power loss)
1 1 1 1
20 25 30 35
CABINET TEMPERATURE °C
Altitude
0:100
100:250
250:500
500:750
17
User's manual
1
0,9
0,8
40 45 50 55
meters f = 3.1 m3k/Wh
meters f = 3.2 m3k/Wh
meters f = 3.3 m3k/Wh
meters f = 3.4 m3k/Wh