Altitude De-Rating For PCS/PF Soft Starters
Do I need to de-rate PCS/PF Soft Starters for higher altitudes of 2000, 3000 or 4000 meters? Above how many feet or meters must I derate the soft starter and what are the derating factors? What are the effects on the PCS/PF soft starter when used at altitudes above 2000 meters and why is derating necessary?
The derating is actually a temperature derating since that is what is going to affect the SCR's within the soft starter the most. The idea is that the enclosure is not going to cool the PCS/PF soft starter at the same rate, at higher elevations and a hotter ambient temperature will be the result of increased altitude. In some cases, a larger ampacity PCS/PF soft starter may need to be used to offset the increased heating effect at high altitudes.
The maximum operating temperature of PCS/PF soft starters is 50 degrees C (122F). Careful considerations must be made to exceeding this limit because of decreased efficiency of fans and heat sinks in higher altitudes. At higher altitudes, to select the product and to eliminate Over Temperature faults use the following guidelines:
PCS and PF controllers must be de-rated at altitudes above 2000 meters (6500 feet). The temperature derating factor is 3 degrees C for every 1000 meters higher than 2000 meters.
Example: at 4000 meters, there would be a 6 degrees C increase in ambient. That means that for an enclosure ambient of 50 deg. C, you may want to upsize the starter by one size since the equivalent enclosure would now be 56 degrees C. If, on the other hand, the enclosure ambient is 6 degrees less than 50 degrees C (or 44 degrees), no derating would have to take place at all.
For worst case scenario where the enclosure ambient temperature is not known, select the next highest size in amps of the PCS/PF soft starter when exceeding 2000 meters.
For additional information please contact your nearest authorized distributor, sales representative, or call our customer service or technical support lines.