based on machine design:frictional loss ,windage loss,rated speed you need to calculate.

based on rotor design :rotor outer diameter ,yoke thickness , length of machine.

based on slot:slot type you should chose,then basic bs0,bs1,hs0,hs1 should be calculated

based on pole design:pole embrance from value 0.1-0.9 should be found then ,magnet thickness, pole arc value should me found.

adding finally first of all you should consider at what rated speed rated power machine run or you going to design.

then proper material should be choosen for stator and rotor conducter  ,

finnaly i suggest for analytical design reffer basic electrical machine design book. value and sample calculation will be given there. for software design (in ansys maxwell/magnet) ref youtube.

Your question is rather vague. You need to know first the power/torque/speed rating you want and the allowable machine size (because you can do anything, and very badly, if you are not space-restricted). About your design parameters, is this because you see too many and don't know on which one you should focus? If so, tell us which type of equations you consider and we could give you insight on which ones have the most influence (generally, PMs remanent flux density, number of poles, etc.).

Add precision and I will complete my answer ASAP.

Hi,

Below parameters are essential to design a bldc,

1) Speed and Power

2) No of Pole

3) Electromagnetic torque and cogging torque

4) Air gap length & airgap flux density at stator teeth and airgap and flux / pole,Current density

5) Voltage

6) Current 

7) Slots/pole and mmf , Winding SWG, number of turns/slot Fill factor & winding and end winding impedance at the desired driving frequency

8) rotor&stator Diameter Slot/Tooth dimensions,back iron length, Stack length

9) No of phases

10) No of slots (Stator/Rotor as per the need)

11) Magnet dimensions (width,length,Breadth)

12) Core material,PM material selection

13) Eddy current and Hysteresis losses 

14) V and I Harmonics

15) Yoke and shaft dimensions

16) Insulation class and temperature raise

Hope this can help..

Thank you sir, but you have some formulas while designing it. if it is available then send it to me.

i want to design a 3 phase, 36V, 350W bldc motor.

Hi Mahesh,

You can convert Km/hr to rpm if you know the disc/wheel diameter.

you can refer any Rotating electrical machine/Synchronous machine book to start your design(like.,Electrical machine design by A.K.Shawney/Design of rotating electrical machines / Juha Pyrhönen, Tapani Jokinen, Valéria). You can also use the below online tool to get free to simulate the performance. it may also guide you to finalize the winding configuration and slot numbers.

http://www.emetor.org/

Thank you sir for giving me valuable information.