Cooling Of Inverter Enclosure - Mitsubishi Electric FR-A700 Technical Manual

3.7.4

Cooling of inverter enclosure

(1) Cooling method
The enclosure housing the inverter must efficiently
dissipate heat generated by the inverter and other
devices (transformer, lamps, resistors etc.) and heat
entering from the outside, e.g. direct sunlight, to keep
the temperature inside the enclosure less than the
permissible temperature of the equipment in the
panel including the inverter.
The cooling systems are classified as follows in
terms of the cooling calculation method.
1) Cooling by natural heat dissipation from the
enclosure surface (totally enclosed type)
2) Cooling by heatsink (aluminum heatsink, etc.)
3) Cooling by ventilation (forced ventilation type,
pipe ventilation type)
4) Cooling by heat exchanger or cooler (heat pipe,
cooler, etc.)
Cooling system method for inverter enclosure
Enclosure
Cooling Method
Structure
Natural
ventilation
(Enclosed,
open type)
Natural
ventilation
(Totally
enclosed type)
Heatsink
Heatsink
cooling
Forced
ventilation
Heat
Heat pipe
INV
Comment
Low in cost and generally
used, but the enclosure
size increases as the
INV
inverter capacity
increases. For relatively
small capacities.
Being a totally enclosed
type, the most
appropriate for hostile
environment having dust,
dirt, oil mist, etc. The
INV
enclosure size increases
depending on the inverter
capacity.
Having restrictions on the
heatsink mounting
position and area, and
INV
designed for relative
small capacities.
For general indoor
installation.
Appropriate for enclosure
INV
downsizing and cost
reduction, and often used.
Pipe
Totally enclosed type for
enclosure downsizing.
(2) Cooling effect calculation
1) Calculation of heat dissipation energy by natural
heat dissipation from enclosure surface:
W1=K1 A
W1 : Heat dissipation energy per second [W]
A
: Effective heat dissipation are [m
: Temperature difference between inside
t
and outside the enclosure [
K1 : 6 [W/m
(a) The effective heat dissipation area does not
include constructions, such as a floor and
walls, and any surface proximate to the other
enclosures.
It does not include the installation areas of
vents, heatsinks and heat exchange either.
(b) The temperature in the enclosure should be
kept constant by an agitating fan.
(c) Constant K1 is indicated as a reference value
because
structure, parts layout in the enclosure, and
ambient temperature.
2) Calculation of heat dissipation energy from
heatsink:
W2 = N K2
W2 : Heat dissipation energy per second [W]
N : Number of heat sink units [pieces]
t :Temperature difference between inside
and outside the enclosure [
K2 :Heat dissipation capability of one heatsink
unit [W/
3) Calculation
ventilation:
Q
W3=K3
60
W3 : Heat dissipation energy per second [W]
Q
: Air flow [m
: Temperature difference between inside
t
and outside the enclosure [
K3
: 1160 [J/m
4) Calculation of heat dissipation energy by heat
exchange or cooler:
W4 = K4 H
W4 : Heat dissipation energy per second [W]
H : Cooling capability [kcal/h]
K4 : 1.16[Wh/kcal]
549
SELECTION
t
2
]
]
2
]
it depends on the enclosure
t
]
]
of heat dissipation energy
t
3
/min]
]
3
]
3
by