limits of LDU?

[Parish8]

has anyone pushed a tesla ldu to the point of breaking it or smoking something? I would like to use some typical hotrodder techniques and push a "performance" ldu until it breaks. then see if that part can be upgraded. then push it harder. my racing is typically floor it for 6 seconds(1/8th mile) and then let it cool down for 1/2 an hour. for tuning purposes i will be on a dyno at first and then the track and hope to be set up to log anything worthy of logging.

i am new to this and have lots of questions.

when using the tesla ldu are we using the factory igbt's and the board controls those? when i ask for more power are the only electronic things that are likely to burn up the igbt's or the motor itself? if the igbt's burn up are there better alternatives? can they be located outside the drive unit if the new one wont fit in the factory location?

how do we get more power? if i am reading the info correctly the igbt's only control voltage and the current is determined by the impedance of the motor? it looks like you would use boost and fweak to get to max power sooner? then after that you are limited by the battery voltage? assuming battery current is not a limiting factor can you just add more cells for a higher voltage and get more motor power? what is the max pack voltage? could you make a 700volt pack?

i have a many questions but lets see where these lead. if there is a better place to be asking this stuff let me know.

[johu]

The IGBTs are 600V parts. So I'd say 450V is the limit. You can try pushing it. It will not increase torque, just the speed with full available torque.
They may not use the strongest IGBTs on the market so you can look into upgrading. Standard TO-247 package. Mind you its quite a mess because they are enclosed with gel.
6s is not long, you could try chilling the inverter.
Good LDU parameters here: https://openinverter.org/wiki/Configuration_Files

[tom91]

You would be surpised how out of spec you could actually pull a base unit.

We need some better logging equipment but we have seen in excess of 1500 Amps DC into the 'base' inverter.

[P.S.Mangelsdorf]

You would be surpised how out of spec you could actually pull a base unit.

We need some better logging equipment but we have seen in excess of 1500 Amps DC into the 'base' inverter.

Tom, what have you seen for torque out of a base unit? All the resources I've been able to find seem to indicate the sport unit is capable of a significantly higher torque rating (600Nm vs 450Nm).

If its possible to get more than that out of a base unit, I may be able to start my build with that and swap to a sport unit later. Money and time are tight on my build but I want/need good performance, I'm building a 1/4-mile street/strip car.

[tom91]

Yes start with the base unit, should do more than 450Nm.

I currently would be more worried about getting the drive unit not to blow apart your axles and break the wheels loose.

[Parish8]

You can get killer axles custom built and traction can be sorted out. Not sure when the diff itself might blow up.

I am not clear on some of the basics. Once you reach your fweak number are you at full voltage and as much current as the motor can flow? At this point is the only way to make more power by increasing the pack voltage thereby increasing the motor voltage?

[Parish8]

The IGBTs are 600V parts. So I'd say 450V is the limit. You can try pushing it. It will not increase torque, just the speed with full available torque.

It sounds like you just described making more hp. No more tq but it holds the tq higher into the rpm’s which results in more hp and going faster. That sounds good to me. What limits the tq?

If using a volt battery you could add one module at a time. Likely get by with one extra 48v module? Maybe try 2 at some point.

[tom91]

I am not clear on some of the basics. Once you reach your fweak number are you at full voltage and as much current as the motor can flow? At this point is the only way to make more power by increasing the pack voltage thereby increasing the motor voltage?

No the current is inveter limited.

Getting batteries that can deliver more current without too much sag is the best way to get more power. Any sag is heat lost in the battery, so power wasted.
You can try and offset this loss by increasing pack voltage, but this will just net you the few little percent.

If you need more 'launch' and the whole drivetrain can take it, you just keep increasing the phase current until you blow your igbts.

So quick summary:

Low end power/torque = Phase current : IGBT current limit
Mid range torque/Power transition = Battery Voltage (and sag) at the required current to generate max phase currents.
Top End Power = Thermals of battery and IGBT, so both will start performing worse due to heating up.

On the Zero-EV drift car we run Tesla tires, but then semi slicks.

Not fully dialed in but here is a run she did at short track.


So sag at 1000A+ is quite substantial

[P.S.Mangelsdorf]

Yes start with the base unit, should do more than 450Nm.

I currently would be more worried about getting the drive unit not to blow apart your axles and break the wheels loose.

I'm building a custom rear suspension using Mustang parts because its going in a car that currently has a straight axle. Planning on custom axles.

I doubt I'll have much issues with the wheels breaking loose. I'm putting batteries behind the driver's seat about 1-2 feet in front of the axle line, and will be using wrinkle-wall slicks.

From what I understand of your other responses, torque is controlled by an inverter setting and limited by the IGBTs (assuming a battery of sufficient capacity). Is that correct?

[Roadstercycle]

I think Jon Volk just found the limit.

[P.S.Mangelsdorf]

I think Jon Volk just found the limit.

of the stock diff at least

[jon volk]

Hopefully I don’t find the limit on a Quaife diff.