I don't understand how people are making a BLDC Motor with 95% to 97% efficient. I myself is a Motor Design Engineer and i use my own Excel calculations for designing various BLDC Motors. Even i use Ansys Software for designing the Motor. But the maximum efficiency i got while designing the Motor in Ansys was 90% and the Motor was an Outrunner. For Inrunner, i could go up to 87%. But when i go through different papers on internet, i see the efficiency of all motors to be around 96% to 97%. I don't know how people are achieving it. Do they actually get that efficiency in practical?
My Motor practical efficiency was 85.4% (Full load) only even it was showing around 90% in Ansys software.
Now can anyone tell me where did i go wrong? And please if anyone has practical Motor designing experience then please tell me how i can design a BLDC Motor with atleast 95% efficiency in Ansys or any other softwares such as Speed or Motorcad? And how to get that same efficiency when the Motor is made practically?
Yes it is quite possible but it costs. To have high efficiency like 97% have to have low current density in windings of the machine. Instead of normal current density for example being 6A/mm2 You would make windings with larger cross-section and limit current density to 3-4A/mm2 and it costs space the Cu material. The losses in windings will drop with the square of ratio that You diminish the current density. You have also to pay attention to ferromagnetic material losses in rotor which means good steel with small specific losses and thin steel sheets.
Piotr Wach, Opole, Poland
Thank you very much Wach for answering.
Put the fabrication and Manufacturing aside, first I wanted to know whether we can atleast design a Motor with 97% efficiency in Ansys or Speed Motor Design softwares.
If yes, how?
Because i have tried my all efforts to design my Motor in Ansys to get an efficiency of atleast 93% but I couldn't.
My BLDC Inrunner Motor efficiency was 87% and Outrunner Motor was 90%.
Now what should I do? I have come to a dead end. I hope that you will help me out because i am not getting help from anyone and you were the first one to atleast respond. I think you also have a profession from Motor side.
Anyway I once again thank you Wach for answering.
Now I do understand better Your problem. Normally in practise if You want You to have high efficiency You have to run the machine with nominal speed and more than 60-70% of nominal load. Having that You have to limit losses as much as possible - that is losses in a converter switches, losses in windings of a machine, ferromagnetic losses in magetic core and least important losses depending on angular speed - that is damping of rotary movement.
In the stage of mathematical modeling it means a change of several patrameters in that model. The most important are resistances of the swichtes of the converter that conduct the main current and also the transition time of the switches. These losses depend also strongly on switching frequency. Than You have to limit losses in windings, which means smaller values for resistances of the windings - these reflects smaller current density of current in the windings. Finally, which is less important You have to raise value of resisnance RFe - reflacting losses is magnetic core and diminish parameter D responsible for mechanical losses connected to rotational speed of the rotor. That will change the efficiency of the drive towards higher values.
Good luck in further attempts - Piotr Wach, Opole, Poland.
My doubt is not completely clarified but anyway thank you Wach for responding and answering the questions. Thank you very much.
Follow electric machine design book MG SAY and AK Swahani....For Conventional PMSM (surface mounted) the efficiency can be take as 95% for 100kW and above. as we know motor input kVA/input power is proportional to volume cube of machine where as motor loss is proportional to volume square of machine. so, higher the volume of the machine (of course for any particular type) higher the efficiency...the advantage of bldc/pmsm not in efficiency but in power density, torque density and no-load loss with respect to conventional machines.
- Badges
- Science topic
- Similar topics
- Engineering
- Control Theory
- Control Systems
- Control Systems Engineering