Designing a BLDC motor 1

[Malik009]

Hello everyone. A complete newbie here. I recently started a project of designing a BLDC motor for a ceiling fan that consumes 20 watt of power and runs at a rpm of 330. The weight of the propeller is 750 gram. I am using a 18 slot core of stamping. The outer diameter is 158mm and stack hight is 4 mm. The number of magnets I am using are 16 and they are ferrite magnets. The have a gauss rating of the magnet is 18 gauss. So far I have only collected some current rating of an existing ceiling fan that actually consumes 50 watts. But at 20 watts this fan consumes 0.10 amp. I want some guidance regarding formulas that I can use to calculate the appropriate wire guage and wire turns that would be needed to pull of this project. Any help,advice or resources would be appreciated.

 

[davidbeach]

Homework?

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[waross]

Good to know:
The power will depend on the work done by the fan and not on the motor.
If the fan does more than 20 Watts of work at 330 RPM on a 20 Watt motor the motor will be overloaded and may fail.
The coils and magnets in a BLDC motor are typically spaced 120 electrical degrees apart.
18 slots and 16 magnets may be do-able, but the timing will be complicated and challenging.
Analyze your magnetic circuits with particular attention to the air gaps and determine how many Amp-Turns are needed to achieve your desired flux density.
Iterate combinations of current and turns needed to achieve your flux density.
Be aware that the impedance of your coils may be dominated by the inductive reactance rather than by the resistance.
The inductive reactance will be dependant on the number of turns and on the frequency.

Once you have determined the number of turns and the current, do a Google search for safe current in a coil and see if you will have room for your coils.
If your completed device draws more than 20 Watts you may reduce the current draw by reducing the pitch of the fan blades or by reducing the frequency/speed, or both.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!