Operate the inverter within the ambient air humidity of usually 45 to 90% (up to 95% with circuit board coating). Too high
humidity will pose problems of reduced insulation and metal corrosion. On the other hand, too low humidity may cause a spatial
electrical breakdown. The humidity conditions for the insulation distance defined in JEM 1103 standard "Insulation Distance
from Control Equipment" is 45 to 85%.
Measures against high humidity
• Make the enclosure enclosed, and provide it with a hygroscopic agent.
• Provide dry air into the enclosure from outside.
• Provide a space heater in the enclosure.
Measures against low humidity
Air with proper humidity can be blown into the enclosure from outside. Also, when installing or inspecting the unit, discharge
your body (static electricity) beforehand, and keep your body away from the parts and patterns.
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 contacts, reduced insulation and cooling effect due to the moisture-absorbed
accumulated dust and dirt, and in-enclosure temperature rise due to a clogged filter. In an atmosphere where conductive
powder floats, dust and dirt will cause such faults as malfunction, deteriorated insulation and short circuit in a short time.
Since oil mist will cause similar conditions, it is necessary to take adequate measures.
• Place the inverter in a totally enclosed enclosure.
Take measures if the in-enclosure temperature rises. (Refer to
• Purge air.
Pump clean air from outside to make the in-enclosure air pressure higher than the outside air pressure.
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 given in the previous paragraph.
Explosive, flammable gases
As the inverter is non-explosion proof, it must be contained in an explosion-proof enclosure. In places where explosion may be
caused by explosive gas, dust or dirt, an enclosure cannot be used unless it structurally complies with the guidelines and has
passed the specified tests. This makes the enclosure itself expensive (including the test charges). The best way is to avoid
installation in such places and install the inverter in a non-hazardous place.
Use the inverter at an altitude of within 2500 m. For use at an altitude above 1000 m, consider a 3% reduction in the rated
current per 500 m increase in altitude.
If it is used at a higher place, it is likely that thin air will reduce the cooling effect and low air pressure will deteriorate dielectric
2. INSTALLATION AND WIRING
2.3 Installation of the inverter and enclosure design