Prototype production phase in progress. For pre-orders please send me an e-mail.


1. Introduction:

First BLDC motor was developed in 1962 by T.G. Wilson and P.H. Trickey unveiled what they called “a DC machine with solid state commutation”, it was basically because solid state thyristors appeared on the scene.
A permanent-magnet synchronous motor (PMSM) uses permanent magnets embedded in the steel rotor to create a constant magnetic field. The stator carries windings connected to an AC supply to produce a rotating magnetic field. At synchronous speed the rotor poles lock to the rotating magnetic field. Permanent magnet synchronous motors are similar to brushless DC motors.
The difference between BLDC and PMSM is that BLDC is driven by square waveform and PMSM is drive with a sine wave current.
Because of the constant magnetic field in the rotor these cannot use induction windings for starting. These motors require a variable-frequency power source to start, aka motor inverter, ESC,  Frequency inverter.
I design this motor because i noticed there is no open source motor in the DIY area.
After making my own electric car conversion Opel Agila:, i got enough experience to understand what are the motor needs for an electric car.
A motor should have high range of RPM and high peak capacity to be able to keep the car in one (shift) second or third, and have 120km/h at 7000RPM for example
Many simulations were done until the final version (after about 50 simulations with various magnets sizes, angles, dimensions, stator tooth sizes and shape)
To be able to have a very small cogging torque and a sinewave back EMF the motor is consisted in three rotor slices with 3 degrees skewing; this also reduces harmonics and eddy currents losses in the magnets. The motor will work with a BLDC controller (ESC) using sensorless or resolver method, it needs to be a sinwave voltage controller.

2. Motor sizing, slot pole count:

To decide what is the best motor for your application you need to take in account many of aspects.

  • You start from the power, speed and torque needed.
  • There are many type of motors good for a car conversion ( DC motors, AC motor, Permanent magnets motors (PMSM), Hybrid PMSM ( less magnet material and increased use of reluctance torque), Switch reluctance motor (no magnets, no clogging torque high efficiency, some disadvantages not high start torque, noise and vibrations )
  • For example BMW i3 has a hybrid design between PMSM and switch reluctance motor, by still using some magnets, they where able to create one of the best electric motors on the market.
  •  Higher RPM motors native offer higher power density, because for higher speed you do not need in increase the size of the motor, only for the torque and since the power of a motor is torque multiplied by speed you gain power easy in this way.  Mechanical power at the motor shaft  equation : P[W]=Speed [RPM] * Torque [Nm] / 9.55
  • If a motor has 65kw of mechanical output power the electrical power needed is bigger because of the efficiency. For a car a 60-65kW is enough to have good acceleration.
  • I decided to use 60 slots and 10 poles because this combination is offering 5 symmetries, and high winding factor. 0.966), if you use 12 poles then the frequency becomes to high and the motor eddy currents losses become to high, GM is using the same slot pole combination Chevrolet Volt, also many other producers.
  • We can say that for a higher torque we need more magnets, but also keep the frequency lower than 400-500hz, because higher magnets count will create higher frequency.
  • Motor Frequency calculator : f[hz]= Pole count (magnets nr.) x RPM / 120 Example: this motor has 10 magnets and 7000rpm then f=10×7000/120 = 583Hz. 
  • For this frequency is imperative to use high frequency lamination in the stator like NO-20 or equivalent. Thinner lamination will offer lower eddy currents losses. The thickness for this frequency should not be higher than 0.3mm
3. Choosing the Materials: 
  • Even if in the last 50 years the PMSM motor theory remained basically unchanged, the big improvement was in the materials area, especially in the magnets.
    This days the magnets are very powerful, and this allowed for very high motor densities to become a reality. Also with the use of thinner and thinner silicon steel laminations the frequency of the motors was increased 10 times versus of a conventional AC motor that runs at 60 or 50hz, this resulting in very high RPM and many pole pairs. For example regarding this motor a NO-02 material in the stator (0.2mm thickness) compared with M235-35A materials witch is 0.35mm thick, will give an improvement of 0.5% in efficiency, which is quite a lot can mean 400w of less power dissipation.
  • Neodymium Iron Boron is an alloy made mainly from a combination of Neodymium, Iron, Boron, Cobalt and of other transition metals and with varying levels of Dysprosium and Praseodymium. The exact chemical composition within NdFeB depends on the grade of the NdFeB magnet. Dysprosium and Praseodymium are added to improve the Hci (Intrinsic coercivity) of the “Neo” magnets.
  • Stronger magnets produce more torque so more power in the end. I decided to have N42UH magnets with phosphate coating, Stronger than N42 can not sustain high temperature operation so i stop at N42.

4. Motor topology, calculations and simulations: 

  • To be able to calculate and determine all the parameters of the motor a simulation software is needed, they are extremely expensive unfortunately.
  • Even with a tool to simulate the motor, you still  need to know and understand all the parameters, to determine best motor topology for certain application, so is almost pointless for somebody to try the software if there is no university background for electric motor like me for example.
  • The software can determine many parameters, but it can determine them well if you feed with the correct data, correct materials and correct assumptions.
  • Underneath is the 60 slot and 10 pole model with transparent core to be able to visualize the coils and magnets.
  • Mechanical analysis is done in a separate program to evaluate the centrifugal forces that tend to throw the magnets outside the rotor.

This test is very important because you want to make sure the magnets will not fly outside, but you also want to have them as close to the exterior with bracket as thin as possible.

65kW motor radial flux from Iulian Berca on Vimeo.

Stress analysis. A force of 2700N was applied to each magnet in outer direction to simulate the centrifugal force produce by the rotor rotation at 7000 RPM. The limit force for the material is about 250 Mega Pascal. So we are way under the limit.

Motor simulated at different parameters and loads


Main Electrical characteristics:

  • Peak Power …………………………………….130Kw, 1min.
  • Nominal Power(S1 continuous) :……… 65 kW
  • Max speed: ………………………………. 8000 RPM
  • Supply DC bus Voltage: ………………… 280Vdc
  • Supply DC bus Voltage: ………………… 280Vdc
  • Peak Torque :………………………………………… 200 Nm
  • Very low cogging torque (Zero current)………….. 2,5Nm (lower than 1% of the motor torque)
  • Ac Supply……………………………………. 151 VAC
  • Turns: 2, parallel paths: 4

  Mechanical Characteristics:

  • Slot count: ……………………………….. 60
  • Pole count ……………………………….. 10
  • Stator OD : ……………………….. 255mm
  • Stator ID : …………………………. 180mm
  • Rotor OD: …………………………. 178.4mm
  • Machine core length……………. 80mm

Flux distribution animation in the motor at maximum current, click to view the gif

The video represents the flux polarity, is displayed radially. As we can see the field is moving form coil to coil in front of the magnets.

The motor has big peak capability ~2x and enough iron not to saturate the core. At continuous operation the flux in the tooth and back stator is not higher than 1,5T



    Winding distribution and parameters:

65kW Permanent magnet synchronous motor

  • Connection Type : Star
  • Number of parallel paths: 4
  • Number of turns: 4
  • Wire diameter 0.61mm
  • Number of strands in hand 23

Calculations: Conductor area is 6.75mm2 per each path. Using 0.61mm diameter wire we end up with 23wires in parralell.
Since we have 4 parallel paths total conductor area will be 6.752 x 4 = 27mm2 resulting a current density of 9,63Amp RMS/mm2. With a water jacket around the motor to cool down, the motor temperature will be about 90 degree celsius from the simulations.

The efficiency map in Non linear mode took 5 hours to simulate with core i7 7700 processor. In practice we expect some variations due to the materials, and motor construction tolerances.

Motor Length (no shaft): 185mm (~7.3 inch) Diameter: 287mm (11,29 inch) Mass: 33kg (72 pounds)




  1. Stator Drawing Download: PMSM Stator design 65kW
  2. Rotor Drawing Download: Updated version soon.
  3. Magnet Drawing Download: PMSM Magnet 40x15x8
  4. Stator Rotor 3D pdf Assemble: Motor Core design 65kW Note ( the 3D pdf can be opened only in Adobe acrobat reader) Chrome will not work.

3D Cad files:

All the info in this article is open source for non commercial use only.

For those interested and able to manufacture the casing i can also sell stator and rotor core + magnets kits.

The silicone steel laminations are now manufactured. I`m looking now for the casing and shaft manufacturers. The motor will be available in US and EU.

The US partner is Brook Drumm from

For EU sales contact is myself at about menu.



  1. Looks like an interesting project.

    If you need any volunteer help fabricating some parts, contact me, I have a well equipped CNC machine shop.

    • iulian berca says:

      Thank you for your support, actually i am looking for somebody to make or help with the parts.


      • Sounds like fun.

        My equipment list is:

        2 CNCs largest one has 762mm travel, very accurate Mori Seiki.
        A Webb lathe
        OD Grinder
        Surface Grinder
        TIG Welder
        Sunnen hone

        I can help with making prototypes but don’t usually do any production.

        You can send me any CAD files or drawings with information about materials, tolerances and finishes etc. I have never made an electric motor but I am interested in the subject.
        I have built an electric bike (hub motor).
        Would like to build a very powerful electric motorcycle some day.

        • iulian207 says:


          Very nice, i will soon finish the cad drawings and i will attach them, or everyone to download, a cnc lathe with live tool was nice if you had it.
          But we will see what we can do.


  2. Brook Drumm says:


    I am Brook. I own an open source 3d printer manufacturing company – Printrbot.

    I am designing an open source electric vehicle that is unique in a few interesting ways. To be truly open source, I have found an open source motor controller that can power up to 200kW!

    Now I am looking for an open source motor. The car is really a one seater around-town NEV. I live in Lincoln, California and there are many NEVs- I own one. Since I have access to tools, machinists, electrical engineers, etc… I’d love to see how I can help you.

    I must say, this looks like a perfect match for crowdfunding… in 2022, I raised $831K for my 3d printer- it can work.

    Anyway, feel free to reach out if I can help in any way.


    • Berca Iulian says:


      I`m interested in a crowdfunding, we can work together to make the best motor on the market but also with a very low price.

      Please write me an e-mail on my private email address, found at my website top in About menu.


  3. Jack Hann says:

    Very interesting job.
    If i want to order your motor for my drone, the price includes controller and inverter, or not?
    please write a email to me with the prices to your 35 45 65kw motors, thank you very much.
    I’m very interesting at your project, if it is possible, i also want to be part of your group for crowdfunding and marketing. I live in Germany, not too far.
    Liebe grüße.

  4. Karms says:

    Hi, when your motor will be open source and when will you make another post?

  5. Berca Iulian says:

    I should finish soon, it within a week let`s say. Is depending on my available time.

  6. Miguel Camus says:

    Hello mate! What about halbach configuration for the rotor? It seems to be the last tendency!

    • Berca Iulian says:

      hi, Thank you for your suggestion, i`m well aware about callback array, but in this motor is not applicable.


  7. Olivier says:

    Hi Iulian,
    Very interesting project.
    If possible interested to be part of your crowdfunding group.
    One question, did you think it possible to create a 80kW brushless motor working at 560 rpm normal speed. By this way i cannot use reducer ….

  8. Soren Saket says:

    I’m really interested in making my own motors and this has confirmed to me that it’s doable. The problem is that I don’t have an electrical engineering degree (yet), and I can’t find that much useful information on the internet. I would love if you could make some in depth video/text tutorials on the process of creating a motor. Would help me and others out a lot.

  9. Tom W says:


    I would be really interested in using one of these units to build an electric motorcycle.

    Will you be sharing all the details to build one yourself, or selling the motor / kit?

  10. Nguyen Dang Trinh says:

    Hi my Colleague,
    I am Trinh From Praxis Viet nam. Our colleague, Khank gave me your web, and i am impressive with you provide.
    When i was in Holland in 2016. I didnt meet you.
    Nice to see you.

  11. Nish says:

    Which software did you use to get the simulated specification sheet and FEA?

  12. Alberto says:

    Hi, great open source project!

    Please, can you an assembly file or the size of the parts (magnets size angle and position, air gap, …)?

    Thank you so much

  13. Sill says:

    very interesting

    I have a question regarding stator insulation. what did you use to insulate windings form stator.
    By watching your ohter videos, I have noticed that there is something in between yet I have no idea what is the name of this material!

  14. Gaurav Amberkar says:

    I have some questions and I request you to answer.

    1. What software you used for modeling PMDC. I am having difficulty in JMAG. The weight is quiet alot I am getting in evaluation in JMAG. any other software recommendation?

    2. what material to use for rotor stamps.

    3. How to choose right input voltage and current for ev motor. Inguess 500 Volts would be sufficient to get my motor running with continuous power of 110 kw.

  15. Erick says:

    Hi julian i have a question, which magnetic simulation software did you used ?

  16. Caleb says:

    Thanks Julian!

    Will you be releasing the STEP files or just these PDFs?
    I look forward to making a motor and testing it out!

  17. Giovanni says:

    Hello to everyone,

    where can I buy the sheets for rotor and stator? Someone can suggest me a supplier?

    Thank you!!!

  18. Noah Pravecek says:

    Can you post the motorcad files for this motor? I’m trying to change up some parts of it myself and would like to be able to motify it in MotorCad if it’s possible.

  19. Alberto Cesare Barbon says:

    Hi Iulian,

    I realized a little piece of the stator and 3d printed that to try to do two/three wind tests.
    I can’t wind more than three turn with 23 conductors in parallel.

    Be careful, thanks however for your support.


  20. Caleb says:

    The STEP file is in the PDF document and can be extracted.

  21. John Russull says:

    Where can I get laminations laser cut ?
    I live in Cambodia and laser cutting here only works on ( non-magnetic ) stainless steel – with transformer lamination steel it does not cut cleanly. It is very tedious punching out laminations by hand !
    I would like to email a CAD file and receive cut laminations by post ???
    I only need small quantities for now.

  22. Tõnn says:

    Hello, your introduction says 3 slices, but the final design seems to say 2, did that change during the development of the motor and if so, then may I ask why?