Motors that can start and accelerate when they are directly connected to line voltage without the need for a controller, operate at synchronous speed, and achieve Super Premium Efficiency levels.
Line start permanent magnet (LSPM) motors provide high torque, operate at a fixed synchronous speed regardless of load, and are suitable for driving low-inertia loads. LSPM motors come in the same frame sizes as conventional induction motors. Because there are no resistance losses in the aluminum rotor cage, LSPM motors have higher efficiency than Premium Efficiency motors and can achieve Super Premium Efficiency levels. Tests indicate that they perform two efficiency bands higher than Premium Efficiency motors. They operate with the same current and power factor as Premium Efficiency induction motors and do not require a feedback device or encoder.
LSPM motors should work as intended and have advantages in applications involving frequent starts and stops because the PM motor has low inertia. One motor manufacturer offers NEMA Design A LSPM motors rated from 1 hp to 10 hp at a synchronous speed of 1800 RPM, and from 1 hp to 5 hp at 1200 RPM. Super Premium Efficiency LSPM motors should be considered for applications where the motor is in use for more than 2,000 hours per year.
LSPM motors come in the same frame sizes as conventional induction motors for the same motor rating. This makes them attractive replacements for conventional standard efficiency AC induction motors because mounting bolt locations and shaft heights are compatible. They also have the same current and power factor ratings as Premium Efficiency induction motors. No controller or feedback device is required, but they are compatible with adjustable speed drive operation.
Status:
Baseline Description: Standard Efficiency Motor Baseline Energy Use: 5835 kWh per year per hp
Line start permant magnet motors run at a synchronous speed regardless of loading. The efficiency of a 5 hp 1800 RPM motor is about 91.2% making it a "Super Premium" efficiency motor (Source: Dale Basso, WEG, "WEG Quattro Super Premium Motors"). A normal Premium Efficiency 5 hp TEFC 1800 RPM motor would have an efficiency of about 90.1% (Source, U.S. DOE MotorMaster+ software tool). The standard efficiency motor that the line start motor would be a replacement for would typically have an efficiency of 84% when 75% loaded. Energy savings are about 2300 kWh per year when the LSPM motor is used to replace the standard efficiency motor. This calculation assumes a 75% loaded, continuously operating motor. Replacing the standard motor with a conventional premium efficiency motor would save about 1976 kWh/year. The LSPM motor thus provides a total enegy use reduction of 7.9%, exceeding the 6.8% obtainable with the Premium Efficiency motor. Beware of centrifugal loads, however, as the LSPM motor operates at synchronous speed, which may be 20 RPM faster than the PE motor. This is not of concern when centrifugal loads are belt drives and pulley adjustments can be made.
"Typical" Savings: 8% Energy Savings Reliability: 3 - Limited Assessment
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
EERE, 03/10/2011. Energy-Intensive Processes Portfolio: Addressing Key Energy Challenges Across U.S. Industry Energy Efficiency & Renewable Energy
WAPA, 01/26/2011. Technology Spotlight: Consider Choosing 'Super Premium' Motors Energy Services Bulletin