Transcription of Sizing Transformers - Dongan
1 122 Dongan Electric Manufacturing Companyhow to Determine Transformer kVA RatingsTransformer Load expressed in amperes:Select the appropriate kVA size from the selection charts listed on this page or by using the single phase or three phase Sizing formula listed below. Be sure to select a transformer kVA rating equal to or greater than the anticipated connected load. Single Phase kVA = Load Voltage x Load Amps kVA = Volt Amperes 1000 100 Three Phase kVA = Load Voltage x Load Amps x VA = kVA x 1000 1000 Transformer Load expressed in kVA:Select the appropriate size from the selection charts. Be sure to select a transformer kVA rating equal to or greater than the anticipated con-nected load. Transformer Load expressed in wattage:Convert wattage into a kVA rating by using the formula listed below.
2 Or you may refer to the equipment nameplate to obtain the ampere re-quirements of the connected load. Be sure to select a transformer kVA rating equal to or greater than the anticipated connected load. kVA = Wattage (1000 x Power Factor of the Load)Transformer Load expressed in motor horsepower:Select the appropriate size kVA rating from the motor horsepower charts on this page. Be sure to select a transformer kVA rating equal to or greater than the anticipated load :high Ambient Temperature Applications: Derate the transformer nameplate kVA 8% for each 10 C above 40 C up to 60 C. Consult fac-tory for ambients above 60 C. high Altitude Applications: To allow for reduced cooling at higher elevations derate the transformer nameplate kVA by .3% for each 330 feet over 3300 feet above sea level.
3 Sizing TransformersNote:Increase trans-former kVA by 20% when motors are started more than once per motor ampacity by and respec-tively for 90% and 80% power / Ampacity Ratings for Three Phase AC Load Amperes - Single Phase AC Motor Size1 1 1 / Ampacity Ratings for Single Phase AC Load Amperes - Three Phase AC Motor Size1 1 1
