Mitsubishi Electric FR-A700 Series, Technical Manual

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549
SELECTION
S
E
LECTION
3
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.)
(2) Cooling effect calculation
1) Calculation of heat dissipation energy by natural
heat dissipation from enclosure surface:
W1=K1 A
t
(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 it depends on the enclosure
structure, parts layout in the enclosure, and
ambient temperature.
2) Calculation of heat dissipation energy from
heatsink:
W2 = N K2
t
3) Calculation of heat dissipation energy by
ventilation:
4) Calculation of heat dissipation energy by heat
exchange or cooler:
W4 = K4 H
Cooling system method for inverter enclosure
Cooling Method
Enclosure
Structure
Comment
Na
tu
ral c
ooling
Natural
ventilation
(Enclosed,
open type)
Low in cost and generally
used, but the enclosure
size increases as the
inverter capacity
increases. For relatively
small capacities.
Natural
ventilation
(Totally
enclosed type)
Being a totally enclosed
type, the most
appropriate for hostile
environment having dust,
dirt, oil mist, etc. The
enclosure size increases
depending on the inverter
capacity.
F
o
rc
ed c
ooli
n
g
Heatsink
cooling
Having restrictions on the
heatsink mounting
position and area, and
designed for relative
small capacities.
Forced
ventilation
For general indoor
installation.
Appropriate for enclosure
downsizing and cost
reduction, and often used.
Heat pipe
Totally enclosed type for
enclosure downsizing.
INV
INV
INV
Heatsink
INV
INV
Heat
Pipe
W1 : Heat dissipation energy per second [W]
A
: Effective heat dissipation are [m
2
]
t
: Temperature difference between inside
and outside the enclosure [ ]
K1 : 6 [W/m
2
]
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/ ]
W3=K3
Q
t
60
W3 : Heat dissipation energy per second [W]
Q
: Air flow [m
3
/min]
t
: Temperature difference between inside
and outside the enclosure [ ]
K3
: 1160 [J/m
3
]
W4 : Heat dissipation energy per second [W]
H
: Cooling capability [kcal/h]
K4 : 1.16[Wh/kcal]