Environmental Factors when Choosing a VSD
You should consider several environmental factors when installing a VSD. The following should be checked:
- Ambient temperature
- Harmonic distortion
Minimum and maximum ambient temperature limits are specified for all VSDs. Avoiding extreme ambient temperatures prolongs the life of the equipment and maximises overall system reliability. If the VSD is installed in an environment where the ambient temperature is higher than specified, derating of the power is needed. The cooling capability of the air is decreased at lower air pressure. Above 1000 m derating of VSDs should be considered.
Electronic equipment is sensitive to the environment. For instance moisture, dust and temperature can all influence the reliability of electronics. Reduced reliability causes downtime in the application with reduced productivity as a result. Therefore it is important to choose the right solution for the actual application. Basically, it is important to protect the electronics from a harsh environment. The best way to do that is to ensure the electronics are placed outside of the harsh environment where possible.
In most cases you cannot directly see how critical the environment is, It depends mainly on 4 factors, the concentration of pollutants present, dirt the relative humidity and temperature. Most VSD manufacturers offer these solutions to minimize the effect of the environment:
- Mount the VSDs in a central cabinet with long motor cables. This way the VSDs are remote from the critical environment
- Install air-conditioning in the control cabinet to ensure that the critical environment does not contact the VSDs and other electronics. (positive-pressure).
- Sometimes VSDs are fitted with a cold plate. This means you can place the VSD can be placed in the cabinet and the heat is transmitted outside through the cold plate. Then the VSDs electronics are kept away from the critical environment
- Use a VSD which is fitted with a sealed enclosure. VSD manufacturers today offer an enclosure ingress protection up to IP66/Nema 4X which will protect the electronics from the outside environment and eliminates the cost of a separate enclosure
- Order the VSDs with conformal coating which which will significantly improve protection against chlorine, hydrogen sulphide, ammonia and other corrosive environments
VSDs are usually used by professionals of the trade as a complex component forming part of a larger appliance, system or installation. Therefore note that the responsibility for the final EMC and harmonics properties of the appliance, system or installation rests with the installer who has to ensure compliance with the local regulations.
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