Mandatory minimum installation clearances

Ventilation clearances for Sensor Modules and Terminal Modules

Sensor Modules and Terminal Modules can be mounted directly adjacent to one another.

When mounted on the wall, line reactors and line filters require a ventilation space of 100 mm (3.94 in) above and below respectively.

Ventilation clearances for blocksize format components

PM240-2 Power Modules can be mounted side by side up to an ambient temperature of 40 °C (55 °F). A clearance of 30 mm (1.18 in) must be provided at the front and to the left of the mounted Control Unit or Control Unit Adapter for frame sizes FSB to FSF.

Ventilation clearances for booksize format components

Line Modules 5 kW up to 55 kW Active Interface Modules Motor Modules up to 85 A

Active Line Modules 80 kW and 120 kW Motor Modules 132 A and 200 A

Ventilation clearances for chassis format components

Basic Line Modules

Active Interface Modules in frame sizes FI and GI

Active Interface Modules in frame sizes HI and JI

Power Modules, Motor Modules and Active Line Modules in frame sizes FX and GX

Active Line Modules in frame sizes HX and JX Motor Modules in frame sizes HX and JX

Calculation of internal control cabinet temperature

Control cabinet with forced ventilation

In a control cabinet with forced ventilation, the heat loss P_v passes to the through-flowing air that then rises in temperature by О”П‘. In the time interval О”t, the air absorbs the heat Q = c Г— m Г— О”П‘ = P_v Г— О”t, and at the same time the air volume V flows through the control cabinet (c is the specific heat capacity of the air). Mass m and volume V are linked via density ПЃ. m = ПЃ Г— V applies. When inserted in the formula above, the following equation is obtained: P_v = c Г— ПЃ Г— (V/О”t) Г— О”П‘

The heat loss P_v, that can be dissipated by forced ventilation, is thus proportional to the volume flow

that the fan delivers through the control cabinet and the permissible degree of heating О”П‘ = T_c-T_a

The heat capacity and density of the air depend on the humidity level and atmospheric pressure. For this reason, the equation is dependent on other parameters. To estimate the temperature rise in the control cabinet in a typical industrial environment, c = 1 kJ/kg Г— K and ПЃ = 1.2 kg/m³ can be assumed. This results in the following quantity equation:

with О”П‘ = T_c-T_a

The temperature T_c as the ambient temperature of the components in the interior of the control cabinet can be estimated with the formula given and must be checked by means of measurements for each application because local hot spots can form, e.g. in close proximity to a source of heat or hotspot caused by unfavorable air circulation.

Control cabinet without forced ventilation

A control cabinet without forced ventilation conducts the heat loss P_v generated in the interior to the surrounding air (external temperature T_a) through the surface. For the heat flow,

the following applies in the steady state:

k is the heat transfer coefficient, A is the effective cooling surface of the control cabinet, and О”П‘ is the temperature difference between the internal cabinet temperature and the external temperature О”П‘ = T_c-T_a

The transfer of heat through the walls of the control cabinet is determined by the heat transfer of the interior air to the cabinet wall, heat conduction within the cabinet wall and heat transfer from the cabinet wall to the external air. The heat transfer is to be calculated by the heat transfer coefficient О±, and heat conduction by the heat conductivity О» and the thickness d of the cabinet wall. The resulting equation for the possible heat loss P_v is: P_v = [1/(1/О±_i + d/О» + 1/О±_a)] Г— A Г— О”П‘ = k Г— A Г— О”П‘

P_v = k Г— A Г— О”П‘

Typical values for the heat transfer coefficient k in the case of control cabinets with walls of painted stainless steel which are up to 2 mm (0.08 in) thick:

The calculating procedures of IEC 60890 (VDE 0660 Part 507) can be used for determining the ambient temperature T_c in the interior of the control cabinet. All heat sources in the control cabinet must be taken into account in the calculation, e.g. Line Modules, Motor Modules, power supplies, filters, reactors. It is important to determine the effective cooling surface dependent on the method of setting up the control cabinet. The standard can also be used for control cabinets with ventilation openings (natural convection).

The estimated temperature T_c and the temperature distribution in the control cabinet should be checked with measurements for every application since local hotspots can form, e.g. in close proximity to a source of heat or a hotspot.

Control cabinet with air conditioner

The control cabinet emits heat via its surface and the air conditioner.

Manufacturers provide information on the design of the air conditioner, e.g. Rittal:

http://www.rittal.de/produkte/system-klimatisierung/index.asp