I need it for an AirStar AS50 compressor.

First you need to determine the equipment’s required voltage and current. For example a Statim 2000 sterilizer requires 240 Volts at 11 Amps, 240 Volts x 11 Amps = 2,640 KVA. Choose the higher value transformer which in this case would be the 3500 KVA transformer DCI PN 2969. See the attachment for more FAQ’s on the buck/boost transformer.