23 January 2021
ATS48 softstart sizing for high elevation usage
Derating for high altitude
Maximum operating altitude is 3300 feet without derating. Above this, the softstart will need to be derated by by 2.2% for each additional 330 feet to the maximum of 6600 feet based upon softstart current rating.
40HP 460VAC Soft Starter is normally an ATS48D62Y however if you are going to use this unit at 6000 ft you will need to up size by 1 or more. So you will need to use a
ATS48D75Y for a 40HP 480VAC.
3300 feet is basic rating without derating.
6000 feet - 3300 feet = 2700 feet.
Derate by 2.2% each 330 additional feet.
2700 ft / 330 ft = 8.1818 X 2.2%= 18% current derate of the product.
Soft Starter is rated for 75 amps X 18%= derate of 13.5 amps
or 75amps minus 13.5 amps = 61.5 amps
ATS48D75Y now only rated for 61.5 amps not 75 amps.
Derating Drives operating at 6000 ft will be as follows.
62 amp ATS48D62Y is rated for only 51 amps.