Prototype

The prototype is an 1-phase motor. The typical electric motor will be 3-phase. The 1-phase motor is simpler to construct but has some disadvantages. It will be less efficient than a 3-phase motor and it can’t start itself.

Construction

The prototype dimensions was chosen to enable easy construction. The results are fully scalable to a wide range of motor and generator sizes.

Stator

The stator use laminated 0.5 mm silicon steel sheets glued together. The cross area is 350 mm^2.

The copper wire has 30 turns, with a conductor area of 0.52 mm^2.

Rotor

The magnets used are 24 pcs. of BC22 (neodymium grade N52): 19.2 mm * 3.2 mm * 3.2 mm, 1.44 grams:

http://www.kjmagnetics.com/proddetail.asp?prod=BC22

The laminations consist of 0.5 mm silicon steel sheets glued together.

Motor Dimensions

– outer diameter rotor: 72.0 mm
– inner diameter rotor: 65.0 mm
– outer diameter stator: 64.0 mm
– total average magnetic field length inside iron core: around 45 mm

Results

Use as a motor: Unloaded power consumption 20 V * 492 mA = 9,8 W at operating frequency 270 Hz, 1350 RPM. Power supply: 0 .. 30 V, 1.0 A, 30 W.

Use as a generator: Max continuous output power 60 W at 256 Hz (18,1 V peak unloaded).

Comments on the Results

The power consumption of the motor at unloaded conditions is rather high. The power loss in the silicon steel has been estimated around 3 W but it could be higher. At unloaded conditions a lot of energy is pumped into the motor and back again for each half cycle. The single phase construction in combination with an irregular output voltage is not suited to measure the motor performance. The most interesting part is the generator performance.

The generator results was measured by spinning the motor into speed as a motor. Then the motor drive was turned off electronically and a resistor switched in as a load electronically. The braking effect was notisable as the motor stopped rather immediate. The stated output power was measured using a resistance of 1.36 ohm. Peak output power was 188 W (16.0V * 11.8A). The stated continuous output power has been adjusted to compensate for the output voltage not being sinus shaped.

 
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