Written-Pole® Motor Advantages


True Single-Phase Operation

Belle Written-Pole® single-phase motors are true single-phase motors that do not require phase converters to operate on a single-phase service. The motor's capacitor start/run design is similar in concept to conventional single-phase motors; however the innovative use of Belle Written-Pole® technology allows for dramatically reduced starting currents and increased operating efficiencies compared to conventional single-phase motors.

Low Starting Current

Belle Written-Pole® single-phase motors exhibit starting current requirements comparable to conventional single-phase motors one-fourth their size. This feature reduces annoying voltage sags when starting without requiring users to install complex reduced voltage starters.

Their low starting current dramatically enhances the capability of a single-phase service to support much larger motors than previously thought possible, eliminating the need for costly three-phase service extensions.

Starting and Running Current Comparison
230 Volt Single-Phase

Description Written-Pole® Single-Phase Conventional Three-Phase Conventional Diesel
Rated Output (hp) 75 75 75 (pump hp)
Rated Input Voltage 480 480 NA
Full Load Speed (rpm) 1800 1775 NA
Full Load Current (amps) 116 83 NA
Peak Starting Current (amps) 220 430-575 NA
Operating Efficiency (%) 94.5 94.5 25.0%
Power Factor (pf) Near Unity 0.85 NA
Input Power (kW at Rated Output) 59.2 59.2 179 kW
Input Demand (kVA at Rated Output) 59.2 67.7 NA
Starting Demand (kVA) 101 365-420 kVA NA
Hourly Operating Cost $6.55 per hour ($0.11 per kWh) $6.55 per hour ($0.11 per kWh) $11.26 per hour ($2.60 per gallon)
Monthly Demand Charges Peak kVa demand is lower for Written-Pole® single-phase motors than comparable three-phase motors resulting in lower demand bills where applicable.

Three-Phase Performance using Single-Phase Power

While their low starting current and high operating efficiency eliminate the need for three-phase power in many applications, Belle Written-Pole ® single-phase motors also compare favorably to premium efficiency three-phase motors in many areas. In fact, Written- Pole®single-phase motors often go beyond three-phase performance, enhancing the system's performance by reducing starting current requirements to levels below that of three-phase motors and eliminating the need for reactive power through their unity power factor operation.

Three-Phase Performance Comparison
208 Volt Three-Phase, 230 Volt Single-Phase

  Premium Efficiency Three-Phase Written-Pole®
Rating (hp) 30 30 Equal
Full Load Amps (line) 75 100 33% higher
Locked Rotor Amps (line) 473 185 61% less
Efficiency (%) 94.1 94.1 Equal
Power Factor 0.84 Unity 19% higher
Input Power (kW) 23.8 kW 23.8 kW Equal
Input Demand (kVA) 27.0 kVA 23.8 kVA 11.9% less

Note: Equivalent line current for a 208 volt three-phase Written-Pole motor would be approximately 66 amps. A Written-Pole® single-phase motor's lower starting current and unity power factor operation provide real-world benefits even when compared to premium efficiency three-phase motors.

Download BELLE v. Diesel Comparison