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Discussion in 'Roadster: Technical' started by vfx, Apr 1, 2009.
Changing Our World
From where I sit, that bit of code is the best part of Tesla's "secret sauce".
Their digital motor controls took the industry up a notch.
By the way, I read that TM may not use the motor inductor as part of the charging circuit for Model S. Are they trying to move completely away from all the old ACP technology?
If someone could shed some light on this "inductor function" of motor I would be grateful
Thoughts on EV Charging Interfaces
Not sure how detailed an answer you want. Any wire loop has some inductance (thus makes an inductor). An inductor is one of the basic passive linear electrical components (along with the resistor and the capacitor). The motor, with its many wire loops, of course makes a large inductor. The ACP designs used the motor as a large inductor in the charging circuit, as a clever way of reusing what is available on the car. This was also done on the Roadster.
In my brief interview with JB, he mentions that "version 2" of the Roadster drivetrain would no longer use the motor in this way, yet had better charging efficiency.
Do you have that print reference? I'd be interested to see more detail about it.
I think I got the idea. Battery is DC, motor is AC, inverter just inverts that DC into AC.
While charging you need something that converts the AC back into DC. Part of this something are motor's big stator windings which can store a lot of energy in a form of magnetic field and thus form a strong charger. Charging is not much different than doing regen - when charging AC comes from outlet, when braking with regen, AC comes from motor.
TEG, thank you!
Minor point, but the memristor is also a member of this list.
I'm aware of the memristor, but I didn't think it was linear. The diode is also a passive device, yet non-linear.
I wonder how adding a separate charger mechanism is going to improve the charging capability, and to a large enough degree to be worth the added complexity, expense, space, and weight of a separate unit? I always felt one of the strong suits of the ACP design was the built in charging capability.
I can see two possible reasons right away why they might want to do that:
#1: Higher current capability for the QuickCharge they want. I think I read that the ACP system maxed out around 20-30kW current.
#2: Avoid the need to pay ACP more royalties.
Also, I think they mentioned that they have a new solution in mind that is more efficient which would be another benefit.
An inductor that can handle high current will be quite heavy.
Perhaps the QuickCharge would have the charger external to the vehicle and have a direct DC connection to the pack.
This was one thing someone from Tesla mentioned a while back as a plan for Model S, but then we heard that "standard 480V". This is not DC any more.
Edit: from today's news:
Here we have that external charger again.
"While charging you need something that converts the AC back into DC. Part of this something are motor's big stator windings which can store a lot of energy in a form of magnetic field and thus form a strong charger. Charging is not much different than doing regen - when charging AC comes from outlet, when braking with regen, AC comes from motor."
I have NO idea what the bolded sentence is talking about. Are you saying to hook up AC electricity from the grid to the motor? What do you mean a motor "can store...energy" ? How does an emotor store energy?
I understand how reductive charging works, and I presume it's related to this since TEG posted about reductive charging; can someone explain?:biggrin:
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Phenolic resin insulator / motor isolator (e.g.: G10 or Delrin):
Switch-Mode Power Supplies need windings as part of the circuit.
Here is a small switching power supply:
I think that the reductive charging has a giant version of that with some components in the PEM, and the windings in the motor.
When they say "store a lot of energy", I think they mean just for brief moments as the reductive charging circuit is manipulating the current flow (temporarily converting it to magnetic field energy) to turn various AC voltages into the specific DC voltage needed to charge the battery pack.
(I am basically making educated guesses at all of this though - I don't work with this technology and I am not an EE)
Minor point, but the spline couplers shown here are not made out of Delrin. Looks to me like G10 (or one of it's variants).
Something very strong and non-conductive...
I think the way the charger works is very similar to a "switching buck regulator". Wikipedia has a good summary of it. They use the motor stator windings in place of the inductor in the regulator (the inductor is the most expensive and geometrically large component). To charge the batteries, you need to regulate the current feeding into them; this can be done by modulating the switching duty cycle of the half-bridge (electronically by the car's cpu based on temperature, rate of charge, etc)
... of course I could be wrong.
Which leaves us wondering - if they do away with reductive, do they need to put a big coil somewhere else in the vehicle for the new charger circuit?
Is there another charger technology that they could use that doesn't require a big inductor?
Coincidence, but they use G10 discs in the construction of many Tesla coils too.
"Work in Progress"
SRSG (Synchronous Rotary Spark Gap)
(In the case of the Roadster they don't want the spark to cross the gap!)