If your pivot operation is a "windshield wiper" configuration--that is, a pivot that runs a partial circle and then reverses direction--then you should choose one size larger than normal converter. Under normal pivot operation, only one-half the motors will start at once. However, when a pivot is reversed, all the motors that were "off" when stopped will now start. Thus, a 10 tower pivot may reverse, restarting 7 or 8 motors, and exceed the converter's normal "Start HP" capacity.
The converter should be mounted as close to the single phase service as possible to minimize the heavier single-phase wiring required. The 40 and 50 kVA Rotomax converters are available with an optional soft-starting feature that reduces the starting inrush of the rotary to approximately one-third of normal on start-up to prevent line disturbance.
All Rotomax converters are high-efficiency models. Power consumed by the converter will amount to approximately 5% of the operated load. (For every $100.00 of power required to operate the pivot, $5.00 worth is consumed by the converter.)