[Plamenator]

Actually the motor in the above picture has 8 terminals in total (was a very custom motor ).
The last 2 are for the interpole windings.
Not very familiar with regen, but can the interpoles be used in some way during regen? If regen happens at lower voltages, they may not be needed during regen?

[Tesseract]

Originally Posted by GerhardRP

Am I right that you left the armature and field coils still in series? If so, this configuration is stable. When the generated current increases, the field current drops. If the generated current reaches 200 Amps, the field current would be zero, so zero volts.
EDIT:There will need to be a resistor in the battery circuit to allow the field voltage to fall without shorting the battery.
Gerhard

Yep - this is stable and I can confirm that it works, but even with 50A of field excitation the open circuit voltage of a WarP-9 was only 17V at 3000 rpm. And you can't use a boost converter to step that voltage up because, as you also correctly note, the generated current opposes the field current. This just doesn't seem remotely practical, but it is quite stable.

Originally Posted by Plamenator

Not quite true - both K9" 220V and K11" 250V have field switching which seems to be what you are after...

The pair of 144V K9's that are sitting in front of me right now only have 4 terminals, so any scheme that relied on separating the paired fields and exciting just one of them wouldn't work with these motors (nor the WarP-9, Advanced DC FB series, D&D, etc...).

[GerhardRP]

Originally Posted by Tesseract

Yep - this is stable and I can confirm that it works, but even with 50A of field excitation the open circuit voltage of a WarP-9 was only 17V at 3000 rpm. And you can't use a boost converter to step that voltage up because, as you also correctly note, the generated current opposes the field current. This just doesn't seem remotely practical, but it is quite stable.

So feed it with 500 Amps from a Soliton Jr.

[Agust Sigurdsson]

Originally Posted by Tesseract

Yep - this is stable and I can confirm that it works, but even with 50A of field excitation the open circuit voltage of a WarP-9 was only 17V at 3000 rpm. And you can't use a boost converter to step that voltage up because, as you also correctly note, the generated current opposes the field current. This just doesn't seem remotely practical, but it is quite stable.

This implies that we would require over 400 Amps of excitation current if we want to generate 144 Volts (assuming that is the battery voltage). If we want regen below 3000 RPM we would have to increase the excitation current proportionally.
Designing the DC/DC converter or whatever it takes to generate the excitation current is obviously becoming an engineering challenge.

B.t.w. does someone on this forum know the typical values of the electrical resistance and inductance of the stator alone in large series motors such as Warp-7 thru -9 ?

Agust

[Tesseract]

Originally Posted by GerhardRP

So feed it with 500 Amps from a Soliton Jr.

No-can-do: the source of field excitation needs to be isolated from the traction battery.

Originally Posted by Agust Sigurdsson

This implies that we would require over 400 Amps of excitation current if we want to generate 144 Volts (assuming that is the battery voltage).

It would appear that is the case. I'd hardly call my testing exhaustive, but given that I blew up my 400A constant current load in previous tests 50A was all I could manage with the junk on hand at the shop.

Originally Posted by Agust Sigurdsson

B.t.w. does someone on this forum know the typical values of the electrical resistance and inductance of the stator alone in large series motors such as Warp-7 thru -9 ?

I just have data on the WarP-9 and only for the whole motor, not just the stator. I can make the stator-only measurements this weekend. Note that the inductance is somewhat inversely proportional to current because of saturation.

EDIT: resistance of the field (stator) is 4 milliohms (0.200V drop at 50.0A); I had previously measured 7 milliohms total for the motor and 100uH (based on ripple current fraction at 400A). Once I get a measurement on the field ripple fraction I'll edit this again with the inductance.

[GerhardRP]

Originally Posted by Tesseract

No-can-do: the source of field excitation needs to be isolated from the traction battery.

I'm not sure of that. If the wireing is Soliton1 positive to armature, then field then to Controller minus. The junior shares the minus connection and the plus goes to the top of the field.
Gerhard

[Tesseract]

Originally Posted by GerhardRP

I'm not sure of that. If the wireing is Soliton1 positive to armature, then field then to Controller minus. The junior shares the minus connection and the plus goes to the top of the field.
Gerhard

Yes, that is how it must be wired to even work, but my main concern is that the anti-parallel and freewheeling diodes in Junior provide additional, and undesirable, pathways for current during motoring operation. I quickly sketched your proposed scheme in TINA (a halfway decent SPICE program from TI which is a little easier to use than Linear Tech's LTSpice) to make it easier to visualize the potential gotchas.

It looks like it would only take inserting a contactor in between the field (+) and Jr to solve this problem, but you still must contend with regen only being available at relatively high RPMs, particularly if the pack voltage is high, and braking torque from regen being somewhat unpredictable (though with a known limit due to a known maximum amount of excitation current).

[bruceme]

Originally Posted by Tesseract

Also, regen with the series motor is kind of kludgy because it needs a reversing contactor which might get actuated hundreds of time on every drive if used for regen, rather than just a couple of times if used strictly for reverse.

Since amps are limited by the advance, what about permanently mounting a small 30A controller in reverse, or setting up a second smaller (MOSFET?) reversed gate set (asymmetric h-bridge)? I don't really "need" regen, but I sure would like "engine breaking".

Oh, I'm curious... what's the status? Is this going to release?

-Bruce

[Tesseract]

Originally Posted by bruceme

Since amps are limited by the advance, what about permanently mounting a small 30A controller in reverse

30A through the field won't get you much in the way of regeneration; you need to put at least 200A through it for this scheme to worth the added complexity

Originally Posted by bruceme

...or setting up a second smaller (MOSFET?) reversed gate set (asymmetric h-bridge)?

You can't just reverse the polarity of current through the entire motor, you have to reverse polarity through the field while the armature is spinning in the "forward" direction for regeneration to occur; an H-bridge ain't gonna cut it.

Unless you mean turning the series motor into a hammy-jammy SepEx motor, with a field controller that has beefy IGBTs for the forward direction and wimpy ones for the regen/reverse direction. Sure, that would work, but it would require an entirely new controller.

Originally Posted by bruceme

Oh, I'm curious... what's the status? Is this going to release?

Depends on how much more for a Soliton1 people like you would be willing to pay for it to have this feature... In the range of $0-$50 per controller I am completely disinterested; at somewhere around $100 it doesn't seem so much like a doomed folly and at $500 per I will re-prioritize what I am doing and put this first.

[ElectriCar]

I'm game. It would be worth something for sure to have it for braking and range extension. I wouldn't be interested in using contactors however for switching preferring power electronics instead, no arcing, no clunking, no wear and very fast.