Inverter gross anatomy

[enjoythesilenc]

For academic purposes, I dove into the inverter as far as I dared to. I'm an electrical novice so this is part of learning more about how these bikes actually work.

Inverter lives under the seat. The big round structure is a capacitor, I believe. Mine has a H&C label on it, maybe that is a vendor name?

Flipping the bike over on its back reveals the inverter cover, mine is a cool machined one, others might have cast covers.
Open the lid to see this

The labels say DC bus on the left, which are the terminals on that big capacitor. Wires from the battery pack (top) and the DCCP (bottom) terminate here. Pop the terminal cover off to see which wires go where



Next, pull off the busbars on the "AC tray" so we can see what lurks below. I had to destroy part of the plastic cover with a die grinder because of how it was screwed down to the case.



I think the brain is that big square chip in the middle. It is mentioned in this post: MXR Negative Contact Relay Failure........ . The connectors along the bottom are ENC encoder and MOT motor temperature? You can see some brown compound smeared on the ring lugs attached to the big terminals, which I think is Penetrox, which is called for on this assembly diagram:



Removing that pcba gets you down to this level:



The black rectangular box is the workhorse. I'm not sure if it generically called the controller or IGBT or powerstage or inverter. Any help here?

Mine is labeled as a Powerex which is a company in PA, USA. Powerex - Complete range of IGBTs and HVIGBTs and other Integrated High Power Semiconductor Solutions

Powerex sold this stuff to Mitsubishi, apparently, so we end up here: MITSUBISHI ELECTRIC Semiconductors & Devices: Product Information | Power Modules [IPMs(Intelligent Power Modules)]

(it's a G1 type intelligent power module) MITSUBISHI ELECTRIC Semiconductors & Devices: IPMs(Intelligent Power Modules) G1 series PM300CG1C065

I see a cover attached with screws so out they must come to get us here:



The product literature mentions a "six pack" which I think corresponds to these six black rectangles (IGBTs)? I didn't dare go any deeper as there is potting compound below this circuit board.

The last thing I'll show is the little circuit board labeled "current sensor" sitting upon two of the phase busbars:

 

[VINSANITY]

Great job taking this apart - have always been curious what’s inside so thanks

I actually don’t understand what the inverter does in the system - I’m used to an electric motor with a controller so this is foreign to me.

 

[Rashid510]

Here are some pictures of a bike with more revised inverter components:

 

[Rashid510]

Great job taking this apart - have always been curious what’s inside so thanks

I actually don’t understand what the inverter does in the system - I’m used to an electric motor with a controller so this is foreign to me.

The inverter converts AC to DC in a basic sense. It controls the frequency of the AC current to control the speed of the motor....




HV Disclaimer - If you do plan to open the inverter cover up, discharge the bike and let it sit for 20ish minutes (thats what we used to recommend). HV discharge is not fun.

Overall, cool pictures from @enjoythesilenc. Early bikes had so many differences compared to the newer bikes (example the throttle board was installed into the inverter and not part of the throttle).

That process was one of the most tedious parts of the Alta build. Its a pain once in the bike.

 

[VINSANITY]

I thought the whole system is DC - why does it need an AC converter?

 

[Rashid510]

I thought the whole system is DC - why does it need an AC converter?

I re-read your post, the Alta inverter is pretty much a motor controller. My first line was more in the general concept of a inverter.

 

[Mark911]

The easiest way to really understand what’s happening inside the controller/inverter is to search for the main components and pull up their data sheets. There’s typically a pretty basic description of what the part does at the beginning of each data sheet. That and a little logic will go a long way.
For example, you’ll find the controller side actually has two CAN systems. One dedicated for throttle input and the other for everything else. You don’t want erroneous data or noise on that throttle signal.
Nothing is too complicated. The hardest part is finding the correct data sheet from the cryptic identification each mfg chooses to put on their parts, although some IDs are standardized.

 

[VINSANITY]

Is the Alta motor AC or DC

 

[VINSANITY]

Also what is the PCBA switch - what does it do and where is it on the bike

 

[Rashid510]

Also what is the PCBA switch - what does it do and where is it on the bike

That part has no relation to the inverter. That part is for the OBC (SM only)

 

[hightechnature]

Just to clarify what my friend Rashid510 said earlier, the Inverter takes high voltage DC from the battery and converts it to a 3-phase AC sine wave that is fed to the motor. The inverter also takes the 3-phase AC sine wave created from the rotational kinetic energy of the wheels spinning the motor without throttle input and makes high voltage DC which is used to regenerate the battery. Almost all modern electrical motors do not use brushes like the DC motors we used to play with as kids (speaking for the 50+ crowd -of which I am still barely a member)

The motor controller (managed by the TI TMS570LS in one of the pictures) measures the current and voltage of the generated AC sine wave into the motor and compares it to the battery voltage and throttle input in a feedback loop that ensures stability. The motor controller is sometimes generically referred to as part of the inverter -as it is generally packaged with the power block of the inverter itself (as Alta did). The motor controller is sometimes responsible for managing the PWM (pulse width modulator) duty cycle between the 3 half bridge IGBT (transistors) to generate the AC sine wave. If you want to see a simple video and simple schematic of how an inverter works, check out this video which also details how Pre-Switch technology would give the Alta 5-12% more range.

AOF members are at the leading edge of a giant transition to a new world soon to be dominated by electric mobility. The vocabulary we used to use to describe our the technology innovations housed in our prized chariots of mobility are dying. Terms like 4-stroke, turbo, DOHC, EFI, Octane are being pushed aside for PWM, 3-phase, IGBT, half bridge, WGB, SiC, Inverter and Pre-Switch. Fortunately, we have AOF, Youtube.com and wikipedia to satisfy our curiosity.

I say bring it on. We all know that the Alta is a better bike in almost all ways than the noisy, pollution belching ICE comparables. Give it a little more range and take 30 pounds off and the next Alta like bike will be unstoppable. It is all coming with time and I can't wait.

Happy riding- Bruce

 

[VINSANITY]

Thank you for this explanation - I never really understood the Alta power system until you explained it - I was thinking it was a bigger version of an an electric bicycle but it is actually a mini Tesla (sort of)

One last question, I assume the capacitor stores power so it can be rapidly discharged for quick throttle response - is that what it’s function is?

 

[VINSANITY]

Also I assume the capacitor is used in the regen cycle

 

[hightechnature]

Nope and nope -but good questions.

The capacitor is called a "DC link capacitor". It's primary role is to reduce the current ripple that the battery sees as a result of the rapid and changing (turning on and turning-off) of the half-bridge circuit as the inverter creates a sign wave. Batteries don't like rapid changes in current or voltage because it reduces their lifetime. The lower the switching frequency the larger the DC-link capacitor -which is why the Alta uses such a big capacitor. The Alta has a low switching frequency (Fsw). I don't know ahat is is but I suspect is in in the 5-10kHz -which is what you hear humming when the bike is on no matter if you are moving or not.

You can see the turning on and off voltage wave form in the first picture I sent you. Each up and down line on the scope indicates a switch being turned-on and then truned-off very briefly (you can't see it in the time scale of the graph) and then the next line in the reverse direction is the other switch of the half bridge being turned on. Watch the video in the link I sent. That ripple is sent to the motor which acts like a large inductor. The inductor heats up which is wasted energy and harmful to the motor. This reduces battery range.

https://altaownersforum.com/attachments/1590253054085-png.5421/

In the future, we will talk about full sine wave inverters. They can be built now but they are way too big and heavy -which also makes them expensive (Engineering is about trade-offs). With Pre-Switch technology, a very high Fsw can be used to create a CleanWave output which is and can be made a pure sine wave. This makes the motor much cooler and the energy saved enables higher motor output power for the same battery power. Unfortunately for all of us, Pre-Switch is not easily retrofitted into our bikes. But we are working with multiple EV companies. We are also interseted in working with Zero but so far there is no traction and we are busy with other priorities. An introdtion to the CTO would be helpful as I want one of those Zero RS's in Red.

 

[enjoythesilenc]

I was thinking it was a bigger version of an an electric bicycle but it is actually a mini Tesla (sort of)

This is my impression, too.

Tangential to this nice discussion I see someone tinkering with another powerex igbt inverter to put it in a car, the subject of capacitors being considered, but maybe in a different context.

Time for MORE POWER! 1400a 1200v IGBT controller build! - Endless Sphere