Schneider Electric 58 TRX

Altivar® 58 TRX AC Drives

Installation Recommendations

Calculating Enclosure Size

The equation for calculating Rth (°C/W), the maximum a llo wab le therma l resista nce of the encl osure, is:

Useful heat exchange surface area, S (in2), of a wall-mounted enclosure generally consists of the sides,

top, and front. The minimum surface area required for a drive controller enclosure is calculated as

follows.

NOTE:Contact enclosure manufacturer for K factors.

Consider the following points when sizing the enclosure:

• Use only metallic enclosures since they have good thermal conduction.

• This procedure does not consider radiant or convected heat load from ex ternal sources. Do not inst all

enclosures where external heat sources (such as direct sunlight) can add to enclosure heat load.

• If additional devices are present inside the enclosure, consider the heat load of the devices in the

calculation.

• The actual useful area for convection cooling of the enclos ure will vary depending upon the method

of mounting. The method of mounting must allow for free air mo v em ent o v er al l surfaces considered

for convection cooling.

The following example illustrates calculation of the enclosure size for an ATV58HU29N4 (2 HP) drive

controller mounted in a Type 12 enclosure.

• Maximum external temperature: To = 25 °C

• Power dissipated inside enclosure: P = 97 W (from ratings tables; see page 10)

• Maximum internal temperature: Ti = 40 °C

• Thermal resistance per square inch of enclosure: K = 186

• Calculate maximum allowable thermal resistance, Rth:

• Calculate minimum useful heat exchange surface area, S:

Useful heat exchange surface area (S) of the proposed wall-mounted enclosure:

• Height: 24 in (610 mm)

• Width: 20 in (508 mm)

• Depth: 12 in (305 mm)

Since the surface area of the enclosure is greater than the minimum required surf ace area (1162.5 i n2),

the enclosure is sufficiently large for this particular ATV58 TRX model.

Note that if the selected enclosure did not provide the required surface area or did not meet applica tion

needs, then the following would need to be considered:

• Use a larger enclosure.

• Add a passive heat exchanger to the enclosure.

• Add an air conditioning unit to the enclosure.

Rth TiTo

–

-----------------

TiMax. internal ambient temp. (°C) around drive controller=

ToMax. external temp. (°C) around enclosure=

PTotal power dissipated in enclosure (W)=

Rth

----------= Rth Thermal resistance of the enclosure (calculated previously)=

KThermal resistance per square inch of the enclosure.=

Rth 40°C 25°C–

97 W

------------------------------------0.16°C/W==

S186

0.16

----------- 11 6 2 . 5 i n 2

S2420×()20 12×()224 12×()+ + 1296 in2

front area top area side area