Rotor KV on a TP

[donhuff]

I have noticed before that the AQ magnets seemed to be very strong, for their size.

Is the eturbo used for the purpose of reducing turbo lag? And then when the thermal expansion of the exhaust gasses catches up to, or exceeds, the speed of the electric drive, the emotor turns off. If running on electric continuously, I would suspect that the alternator capable of driving 15 HP would have to be huge and would consume so much of the engines power as to make the whole thing not worth it.

[RaceMechaniX]

Don, for the eTurbo it's used for boost assist to negate any lag and also used for recuperation. So instead of opening a wastegate to dump the energy, you close the wastegate and harvest it. There are also many special modes for emissions and lambda control where the ability to control the turbo speed or boost pressure comes in very handy. The motor is "on" continuously during operation but the amount positive or negative power is adjustable from -100% to +100%. The losses are very low "idling" the eTurbo so not much of a concern.

[NativePaul]

That is a very interesting graph, thanks for posting it Tyler.

For some reason I was assuming that neodymium magnets maintained their strength statically, then fell off a cliff when they got to a certain temperature, I would never have guessed that the strength was linear with temperature.

I was also assuming that the fall of in magnetism was permanent, was I right in that or does it or some of it come back when it cools down?

It is making me rethink my cooling policy, I've always tried to keep my stuff under 60 degrees, but never been too worried about temps as long as it was below that, but if a n52 magnet that has once been to 60 degrees has the same strength ad a n48 magnet that has never been over 30 degrees, I should be more concerned about running temps, and also cars and shade on hot days.

[RaceMechaniX]

Paul,

I believe what you are talking about is the Curie temp of the magnet. This is the point where non-reversible damage occurs. If we operate below the Curie temp the magnet will come back to its original strength when the temperature returns to room temp. All magnets reduce their field strength with increasing temperature and this causes the KV to increase and torque per ampere to decrease. The slope of this change is more drastic for Neo vs SmCo magnet. That is to say, SmCo will produce more consistent torque over a wider range of temps. Compared to Neo which produces best torque at lower temps. So it is very important to try and keep the rotor cool.

I try to keep mine below 100DegC and verify my measuring the coupler temperature after a run which is a good indicator.

permanent-magnets-chart.jpg

I did find a tech article from Novak that some of their rotors are constructed from SmCo. So perhaps Neu is using SmCo, but Neu would need to use a metallic containment sleeve instead of the Carbon or kevlar wrap they use today. The epoxy resin used to hold the filament winding in place needs to withstand the same temp as the magnet and most epoxies will start to reflow around 120DegC.

https://images.amain.com/images/Link%20Images/SmCo_vs_Neo_Technical_article.pdf

[T.S.Davis]

This is a killer thread fellas. Thanks for filling my head with additional data. Much appreciated.

[NativePaul]

Ah yes curie point is what I was thinking of, but couldnt remember the name. Never knew about this temporary effect, grate info.

It sounds like I don't have to worry about motors n hot cars, but I should try to seek out shade at events.

[T.S.Davis]

Pre-cooling motors for trials makes more sense to me now than it did.

[TRUCKPULL]

Pre-cooling motors for trials makes more sense to me now than it did.

Along with that statement, Should be preheating your batteries also.

Larry

[T.S.Davis]

Along with that statement, Should be preheating your batteries also.

Larry

Yeah, I got a little carried away once pre-heating. I used to do it for heat racing too but it's such a PIA.

[TRUCKPULL]

I use a Coolatron cooler, once warmed up it stays at about 100F all day long.
So once that your packs a recharged, you put them in there with the rest of them,
So when you have a heat coming up your packs are all ready to go.
This is very good in the spring or the fall.

Larry

[T.S.Davis]

Wonder if I could plug that right in to my power supply.

[TRUCKPULL]

Wonder if I could plug that right in to my power supply.

12V - it's good.
I have a 12V plug in the back of the SUV, so I can get things warmed up on the way to the pond.
I also have a 110V adapter, so right into the jenny.

Larry



Larry

[T.S.Davis]

That makes more sense Larry. I'm gonna git one too.

I've done heating pads. That's not worth a crap. I also had a similar cooler/heater from Black and Decker that totally sucked. Also tried a great big roaster. hahaha Wayyyyy to hot. Even on the lowest setting. No fire but super close.

[Shooter]

Or you could just put the batteries in your pants. 98.6 degrees.

[jaike5]

Or you could just put the batteries in your pants. 98.6 degrees.

With Larry's internal combustion it could be really dangerous !