A phase converter carries two ratings. The first and most important rating is the Largest Motor HP that the converter can start. This can be a single motor or a combination of motors. For example, starting one 10 HP motor is the same as starting two 5 HP motors at the same time. A 10 HP converter is the proper size in this case.
The second rating is the Maximum or Total HP that operates simultaneously but does not start together. As a rule, a Type MA Phasemaster® converter can run a total of 3 times as many HP as it can start. A 15 HP, a 10 HP and a 5 HP motor (totaling 30 HP) that start separately but run together could run on a 15HP converter. The largest motor to be started is 15HP and the maximum load does not exceed 45HP.
Never add your total operating HP for sizing purposes unless your loads actually start at exactly the same time. If the total HP operating simultaneously exceeds the Maximum HP capability for that converter, increase converter size to a larger model. Use the largest motor for sizing purposes. Consult Kay Industries to verify your selection.
Never size your converter based on total amperage only - you will probably overpay for that much capacity.