Normally operate the inverter within the 45 to 90% range of the ambient humidity. Too high hu-
midity will pose problems of reduced insulation and metal corrosion. On the other hand, too low
humidity may produce a spatial electrical breakdown. The insulation distance specified in
JEM1103 "Control Equipment Insulator" is defined as humidity 45 to 85%.
● Measures against high humidity
– Make the enclosure enclosed, and provide it with a hygroscopic agent.
– Take dry air into the enclosure from outside.
– Provide a space heater in the enclosure
● Measures against low humidity
What is important in fitting or inspection of the unit in this status is to discharge your body
(static electricity) beforehand and keep your body from contact with the parts and patterns,
besides blowing air of proper humidity into the enclosure from outside.
● Measures against condensation
Condensation may occur if frequent operation stops change the in-enclosure temperature
suddenly or if the outside air temperature changes suddenly. Condensation causes such
faults as reduced insulation and corrosion.
– Take the measures against high humidity.
– Do not power off the inverter. (Keep the start signal of the inverter off.)
Dust, dirt, oil mist
Dust and dirt will cause such faults as poor contact of contact points, reduced insulation or re-
duced cooling effect due to moisture absorption of accumulated dust and dirt, and in-enclosure
temperature rise due to clogged filter.
In the atmosphere where conductive powder floats, dust and dirt will cause such faults as mal-
function, deteriorated insulation and short circuit in a short time.
Since oil mist will cause similar conditions, it is necessary to take adequate measures.
● Measures against dust, dirt, oil mist
– Place in a totally enclosed enclosure.
Take measures if the in-enclosure temperature rises. (Refer to page 2-10.)
– Purge air.
Pump clean air from outside to make the in-enclosure pressure higher than the outside-
Corrosive gas, salt damage
If the inverter is exposed to corrosive gas or to salt near a beach, the printed board patterns and
parts will corrode or the relays and switches will result in poor contact. In such places, take the
measures against dust, dirt, oil mist.
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