electrical system
Phase Imbalance Facts:
  • A 5% imbalance = 25% reduction in performance.

  • A motor can't deliver the declared HP running with unbalanced currents and voltage.

  • A 10 Deg C increase in internal temperature = 50% reduced life of the motor.

  • Often loads are centrifugal fans, causing the time to attain operating speed to increase, applying the high current demand on the line even longer.

  • Overload protection is nearly impossible and some manufacturers will not provide current protection if you have a rotary converter.

  • Small 3 phase motors can not be operated without the large motors running.

  • Digital Soft-Start controls are not usable with unbalanced input voltages, rendering the easy start requirements non-applicable.


Phase Voltage and Current imbalance are not tolerated well by the motors.

The 2010 Energy Policy Act has increased efficiency requirements and reduced tolerances for electric motors.

Professional Recommendations

Many utility companies today will only provide 208 Volts VS 240 Volts. Any preexisting single phase motors will not operate properly on 208 Volts. Reduction in performance is inevitable.

Rotary phase converters have significant balancing problems. Some utilities are now requiring soft-start converters to eliminate high inrush demands of the service. In addition many now require soft-starts on motors 20 HP and larger. This is a challenge to deliver under a converter.

Planning Ahead

The best time to consider this system is at the time of your equipment research and purchase. The costs will be very close to that of a rotary converter without the imbalance impediments. The cost is also very close and even less than many two motor systems (dual drive), due to the varied efficiency and coupling expenses.

Example: Legacy System

        Approx Cost  $6500.00

        Approx Efficiency  80%

        2 - 15 HP 1 Phase motors

        2 -  4” 2 gr pulleys & bushings

        1 -  4 gr pulley & bushing

        2 -  15 HP Starters W Overloads

        Requires 200 Amp Service

Example: Our system

        Approx Cost  $ 5100.00

        Approx Efficiency  100%

        1 -  30 HP Motor and pulley

        1  - 30 HP Starter & overload

        Requires 200 Amp Service

single to three phase

The Efficiency Grant program is available to help you upgrade to a better system. Information is available to show savings in operating costs that will provide an avenue to address rebate qualifications.