Very high voltage in high output motors

Some industrial electric motors operate in the kilovolt range, even above 10kv. These motors produce several MW of power, and are badass.

EV trend in performance vehicles is to use higher voltages. Porsche, Koennigsegg use nearly 1kv.

When a controller is involved, lower is generally better as you have less losses thru switching, so I'm told. And obviously high voltage allows lighter smaller conductors for a given power level. Of course there are issues with insulation the higher the voltage you run.

Aside from those 3 things what are the pros / cons of very high voltage in electric motors? Will we see performance cars with voltages over 1KV in the near future?

Id guess the main benefit the big EV makers are after is being able to use lower-C-rate battery packs, yet still get the same power out of them.



Also, not specifically about high voltage, but if youre interested in some of the previous discussions about higher voltage vs higher current systems, there are some threads, at least one of which includes some testing results.

The last thread is just a reference for those that dont already know the issues and how voltage and current in motors works:

https://endless-sphere.com/forums/viewtopic.php?f=30&t=43974

https://endless-sphere.com/forums/viewtopic.php?f=3&t=46000

https://endless-sphere.com/forums/viewtopic.php?f=30&t=47018

https://endless-sphere.com/forums/viewtopic.php?f=2&t=19590

https://endless-sphere.com/forums/viewtopic.php?f=2&t=17345

https://endless-sphere.com/forums/viewtopic.php?f=14&t=4463

Interesting thing about voltage, is that after about 350 volts, you're dead. From 350 to 1000, you're still dead. Above 1500 V, you're dead and cooked, so the neighbours have to smell it...

My point is, provided the drivetrain is designed properly, voltage is just a number. After 1500 V there are HV specific precautions that need to be taken but for most EVs anything between 350 V and 1000 V DC is pretty similar.

The problem is when people take a hobby-battery approach to designing a 400 V battery. That's a sure-fire way to get hurt. Approach it like you're working with a mousetrap with a hair trigger - separation, isolation and insulation.

@Amberwolf - you can't really get more power from a low C-rate cell by going high voltage, but you can get away with less copper.
Like Voltron's nominal voltage being 630 V - we're pushing 290 amps through a 10 Ah pack at full power (183 kW) or 29 C. If I went for half the volts, I would need twice the amps for the same power - 580 amps from a 315 volt, 20 Ah pack, which is still 29 C.

I think 96s is the preferred voltage for most manufacturers because it means the mass of copper required for the charging infrastructure is far more manageable, and the fact that 96s is a pretty convenient number (divisible by 2, 3, 4, 6, 8, 12, 24 and 48).

The motor generators used to power the Bevatron, a very old accelerator where I worked, ran on 12KV three phase AC power. Each of the two motors were rated at 50,000 KVA. They used regeneration to put the stored energy from the main magnet back into the power lines after a pulse was fired into the target. Idle current was about 200A rising to over 4000A at full power. This was all done with technology they had in 1952. Considering the design and build time it was likely 1940's tech from the railroad industry.

https://digital.library.unt.edu/ark:/67531/metadc714502/m1/2/

It is often easier to use high voltage to get high power because the current it takes at lower voltage is hard to manage. Copper busbars get too large, etc.

The technology to manage high power at low voltages is possible but difficult. There is some voltage at which the cost is minimized, using any other voltage raises costs.

For industrial motor applications, higher voltages are used to keep the copper size reasonable and IGBTs tend to perform better in the controllers. This is all mature technology and the cost/benefit issues are very well studied.

But for an EV, you also have to consider the battery. Using a 100+ series cells results in a lot of complexity and things that can go wrong. So there will be sort of a trade off between what's good for the battery and what's good for the motor/controller.