The Evolution of BYD’s Electric Motor: A Lean Design Case Study

Hi, welcome to Monroe Live. I'm Paul

Turble. What we have here are two motors that are from BYD, the Chinese auto

manufacturer, and one from about 2019 and one from this year. uh and we get to see how things have evolved both at BYYD

and kind of in the whole industry. I I

picked these two motors because it shows uh trends in the whole uh electric drive industry. Um but it also shows a a

industry. Um but it also shows a a pretty nice example of lean engineering at work. So what Monroe Associates tries

at work. So what Monroe Associates tries to advise our clients to do are things that were done going from this design to this design. And so lean design

this design. And so lean design principles are were really well illustrated going from this to this. And

you get the kind of results that we're all looking for. Um the big picture is this uh drive unit from here weighs

about 103 kilograms which is not bad.

It's a it's a 200 horsepower drive unit.

So if you go and find try to find a internal combustion engine with a transmission for under 225 pounds, you know, good luck. Uh so this is a pretty

competent and was very competitive at the time drive unit.

This drive unit, the new one is only 86 kilograms. So 20% or more reduction uh in uh in weight and size, but it's and

it's also 180 kilowatts. So good deal more than 200 horsepower. And so you get more power, less weight, and by the way,

lower cost. Uh and everything is better

lower cost. Uh and everything is better quality. And so that's the goal is to go

quality. And so that's the goal is to go from something that is competitive now to something that is much better, less

expensive, does the job better, low less weight, fewer parts, more profitable. And that's the principles

profitable. And that's the principles that Sandy Monroe espoused with lean design concept. And it it's just

design concept. And it it's just fundamental engineering done at every port part throughout the entire process.

And so I just want to go and dive in to these two electric drive units and show you system by system the kinds of things

that they did to get those results. So

first look at the housing. Um this is the original housing. They used this extruded aluminum um housing for the

motor and it was bolted to these two parts to form the motor housing. What

they've done is they moved to an integrated casting where the water cooling channel is integrated right into the the C casting and this casting the

housing the motor housing is integrated right into the the housing for the gearbox. And so they've they went from

gearbox. And so they've they went from four big castings, well three castings in a big extrusion, which had to be

welded, by the way, um to a single casting. And well, this casting plus

casting. And well, this casting plus these two. So four parts to three parts.

these two. So four parts to three parts.

It's as simple as that. you end up with something that is better, will never leak, does a better job cooling, and it's less

expensive. So, again, perfect example of

expensive. So, again, perfect example of the kinds of uh direction that lean design tries to emphasize and that we try to

help our clients move to. So, this was the first example, the housings.

Secondly, in our first video when we talked about this this motor, I talked about the uh let me walk around here to

how they put the the gears and bearings in when they did this assembly.

This side is retained with a bearing retainer plate that requires three screws be put in from this side. When

you put those screws in, you can't see the bearing retainer plate on the other side. You just have to fixture it so

side. You just have to fixture it so that hopefully the screws pick it up and um hold it in place. 99% of the time,

I'm sure it works great. Unfortunately,

some of the time things could be misplaced and the the threads will end up being crossthreaded and you don't get a good fit there and that can cause

issues. We talked about that in the

issues. We talked about that in the previous video. And of course, now in

previous video. And of course, now in the new design, they've eliminated that.

This just goes together Z-axis assembly. every part just drops

Z-axis assembly. every part just drops into the housing and then the housing with all the parts just drops right into the um main housing that holds the

motor. And so they've drastically

motor. And so they've drastically simplified the assembly process, reduced labor time, and eliminated a failure

mode and a part.

So it's it's a win-win. Great better

quality and reduced cost. This is

exactly the kinds of thing that we try to emphasize in our designs as we advise our clients.

So, one part after another, we're seeing these improvements. We see it also in

these improvements. We see it also in the rotor. Now, in the on the rotor and

the rotor. Now, in the on the rotor and the stator, the electromagnetic components, the first thing to recognize is we're

getting more power out of a smaller package. So a big part of that uh 20

package. So a big part of that uh 20 kilogram weight savings is coming out of here. Reduced steel, reduced copper and

here. Reduced steel, reduced copper and very importantly reduced neodymium magnets that there's less magnet material in this motor than there is in

the original. And they're able to do

the original. And they're able to do that with increased power by optimizing this flux path, optimizing

the placement of the of the magnets. The

previous magnets were arranged in this this pattern where you have three

magnets in for each pole.

Three slots here in the rotor for each pole.

And these go in quite deep. So they're

very um almost radially oriented. And so

that means you need to have a lot of magnet material to get in there. The uh

the new design uses a double V um pattern which is much shallower. And

so the there's from a geometric point of view, the flux doesn't have to penetrate so deep into the rotor and you don't have to use as much magnet material to

complete the pole. It's just a a clever way to do it. We talked in another video about these slots and how they've done some clever things to reduce

the torque ripple. So, make the motor torque more smooth and make the flux from the magnets more smooth, which improves efficiency and reduces noise.

So, they've done a lot of great things electromagnetically here uh on the rotor. They've also done some great

rotor. They've also done some great things electromagnetically on the stator and the chief among them is they moved

from a stranded wound stator which is um good for low volume production because the equipment needed to do this type of

winding is less costly than the equipment needed to do this type of winding. But you end up using more

winding. But you end up using more copper when you do it this way. And you

don't have as much copper fill inside the slots. So when you use these bar

the slots. So when you use these bar wind bar wound motors, you can fit more copper in but while still using less

copper overall uh for the design and you end up with uh a more powerful uh and less expensive per part

stator.

Um although it does require again some increase in the uh the tooling costs and and manufacturing costs uh I should say

equipment cost and so when your volume gets high enough it pays to go to this type of design and we seeing the the rest of the industry

um almost everyone exclusively is going to um this style of winding. So there

and almost everyone is going to this style of interior magnet PM machine with this uh shallow V type uh arrangement

for the magnets to minimize magnet material. And so we're seeing a huge

material. And so we're seeing a huge improvement and and a reflection of a trend that is not just at BYD but across

the industry in every OEM is moving from this type of design to this type of design. We're seeing Tesla move this

design. We're seeing Tesla move this way. Uh GM has always been this way.

way. Uh GM has always been this way.

Ford, Hyundai, um, all of the major players are moving towards this type of solution for the electromagnetic design.

I will say that every time in history that you see in the entire automotive industry converge on a single design or

single concept, that's the moment when some disruptor comes in and disrupts the entire industry. And so I would say the the

industry. And so I would say the the electric motor industry is ripe for a major disruption because everyone is kind of converged every to the same kind

of solution electromagnetically for the motors.

Okay. Finally, let's talk about the inverter. And there's a lot here on the

inverter. And there's a lot here on the inverter.

Superficially, the inverters look similar. They're nice thing about it is

similar. They're nice thing about it is they're they're both integrated onto the drive unit. um in a very straightforward

drive unit. um in a very straightforward manner. Um just bolt it straight on.

manner. Um just bolt it straight on.

The new inverter has these switches that are uh cooled on both sides, the underneath and above

with these copper heat sinks. And by

sandwiching the switches between the these heat sinks, the copper heat sinks, they not only get fantastic heat transfer to keep the switches cool and

allow them to run huge amounts of power through a compact package, but also the copper acts as shielding to eliminate or

reduce the electromagnet magnetic noise that the switching creates. Normally

these things act like AM radio stations broadcasting electromagnetic interference all over the vehicle and in particular to the other components on

the control board.

So in order to protect the components from that electromagnetic noise, the delicate um control board with the computer that

controls the whole drive unit is now is located on the opposite side of this casting. So it uses the casting as a

casting. So it uses the casting as a as an electromagnetic interference shielding.

Okay, let's look that. Let's contrast

that to the way they did it before.

Previously, they cooled the switches on one side only. So, the

switches are being cooled with a heat sink that's underneath. This is the traditional way of doing it with the the

control the U gate drivers are on top and then they this is the computer that controls the the switches and they had

to include this stamped aluminum shield to protect the delicate electronics from the noise generated by the switching

devices. So now they've eliminated this

devices. So now they've eliminated this by just locating the control board on the opposite side of the casting. And so

with zero cost and eliminating a part, they get a better quality uh product.

Again, lean design. That's those these are the principles. In the old days, it was just good engineering. It's clever

engineering. Another thing that that this reduction in noise from this uh double-sided cooling patter

around the switches. It allowed them to go to these three small chips to use as their current sensors. So, the current sensors are just these three little

chips that are built right onto the board and communicate directly with the um gate drivers. So, we know we get a direct signal for how much current is

flowing in each phase.

That's much less expensive and [clears throat] higher quality than the old way of doing it, which was to use these big current sensors where each current sensor has

its own iron core wrapped around it.

That iron core isolates it from the electromagnetic noise inside this box.

And so you get a nice clean signal. But

now I need this room for this big core which ne necessitated this big lead frame and these separate components now

need these big wire uh wiring harnesses in order to connect them to the board.

So eliminate the wiring harnesses and connectors like this are the things that cause the most failures in electronics.

Not the electronics themselves, it's the little connectors.

One other thing to to point out is just the cover.

Um the cover on this is a big old casting. Yet another uh thing that you

casting. Yet another uh thing that you have to tool up. Castings are not cheap.

Then you have to machine the casting and then you have to um apply RTV to seal it.

And here they've moved to a stamping uh which once you have the stamping tool made, these are much less expensive. Um

and then they put the seal material bonded right onto the um stamped cover and that ends up making

assembly and disassembly and service much better. So that's the a great

much better. So that's the a great example. I just I really happy to get a

example. I just I really happy to get a chance to show you um what's going on inside of these drive units, particularly the the BYYD Chinese drive

units that um most people don't get a chance to get a good look at u at least in North America. Um so get a chance to get see what's what the competition is

doing and and why um they're to be taken very seriously in this market.

So, thanks a lot. Uh, and we'll see you again on Monroe Live.