What would be the most efficient 1kw motor to use at low RPM

[Fizzics]

...Up to 300 rpm (3 phase motor) and what sort of efficiency could I expect under normal conditions with a small load? Thanks

 

[anorlunda]

...Up to 300 rpm and what sort of efficiency could I expect under normal conditions with a small load? Thanks

I assume you're talking a single phase motor. Too bad, three phase motors are more efficient.https://en.wikipedia.org/wiki/Induction_motor#Efficiency

Full load motor efficiency varies from about 85% to 97%, related motor losses being broken down roughly as follows:[39]

• Friction and windage, 5% – 15%
• Iron or core losses, 15% – 25%
• Stator losses, 25% – 40%
• Rotor losses, 15% – 25%
• Stray load losses, 10% – 20%.

Various regulatory authorities in many countries have introduced and implemented legislation to encourage the manufacture and use of higher efficiency electric motors. There is existing and forthcoming legislation regarding the future mandatory use of premium-efficiency induction-type motors in defined equipment. For more information, see: Premium efficiency and https://en.wikipedia.org/w/index.php?title=Copper_in_energy_efficient_motors&action=edit&redlink=1 .

 

[Fizzics]

Thanks for your reply - actually i meant to say that it is 3 phase

 

[David Lewis]

With a brushless motor, 98% efficiency is not unheard of. It can be designed so that max efficiency operating point of the motor matches the mechanical load.