Soapbox on regenerative braking

Technical discussion on converting internal combustion to electric
Post Reply
User avatar
coulomb
Site Admin
Posts: 3718
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Soapbox on regenerative braking

Post by coulomb » Sun, 21 Jun 2009, 03:42

I had some musings about regen using series wound brushed DC motors on my White Suzi page.

Unfortunately, I got a bit muddled, and forgot about the reversing the field problem.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Soapbox on regenerative braking

Post by Squiggles » Sun, 21 Jun 2009, 04:24

[QUOTE = acmotor]
What sort of emotor do they run in diesel electric locos ? Does following their format help any ? if they deal with big regen. [/quote]

That's a good question. I know they used to mostly be DC of some form, some of the manufactures are moving to AC traction.
I used to work in the passenger car section of a company that also built locos. I have some contacts there still, I will ask.

edit: grammar
Last edited by Squiggles on Sat, 20 Jun 2009, 18:39, edited 1 time in total.

User avatar
coulomb
Site Admin
Posts: 3718
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Soapbox on regenerative braking

Post by coulomb » Sun, 21 Jun 2009, 05:17

My understanding is that the classic Diesel Electric locos used the Ward-Leonard set. That's two DC machines with separately excited (!) fields and armatures connected to each other. By adjusting the field currents, it was possible to create a sort of continuously variable transmission. The diesel engine drove the generator at a fixed speed that suited the diesel; the pitch of the engine never changed much. A bit like a series hybrid, I suppose, but always in oil mode.

Some awesome power flowed through those electric motor/generators. I remember looking into the cabin of one once and saw an ammeter reading some 500 A. I think it was only about 1/4 full scale, too. That was pretty impressive to me at the time.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Soapbox on regenerative braking

Post by Squiggles » Sun, 21 Jun 2009, 05:30

Brochure for one version here.

http://www.getransportation.com/na/en/d ... _motor.pdf


Apparently they are about 500kW each and locos have six of them.
Last edited by Squiggles on Sat, 20 Jun 2009, 19:36, edited 1 time in total.

User avatar
coulomb
Site Admin
Posts: 3718
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Soapbox on regenerative braking

Post by coulomb » Sun, 21 Jun 2009, 05:48

Heh, interesting. From this document on the same site:

      "Historically, DC technology has been the lower initial-cost option for heavy-haul freight applications. However, DC traction motors are found to be susceptible to reliability issues such as moisture, grounding and commutation problems that require significant down time for repair as well as frequent maintenance for brush replacement and extensive cleaning.
      "In contrast, GE’s proven AC traction motors eliminate the electrical problems inherent with DC technology, have no brushes to replace, have fewer parts and require less frequent service than DC traction motors. Compared to DC, therefore, GE’s AC technology improves reliability and availability.

      "Model ES44C4 also features a top end speed of 75 mph compared to 70 mph for DC."

They seem to be 3000 Horse Power locos (2.2 MW).
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Soapbox on regenerative braking

Post by Squiggles » Sun, 21 Jun 2009, 05:57

I am not sure about "increased reliability". Anecdotal evidence would suggest that the new 92 class locomotives in NSW have some issues. Whether these are traction motor related I don't know, could be many other things.
I would certainly expect maintenance costs would plummet though.

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Soapbox on regenerative braking

Post by acmotor » Sun, 21 Jun 2009, 06:01

looks like a similar story from Siemens...

http://references.transportation.siemen ... div=6&l=en

"The benefits of the three-phase technology include low maintenance and a compact design of the three-phase traction motors as well as high starting and continuous tractive efforts. This enables CSXT to run trains with two SD 70 MAC locomotives instead of three conventional DC locomotives."

But this wasn't meant to be a DC/AC question. Image
It was just that regen on locos had been raised and I wondered if there was some helpful info on regen from that area.

Other sites seem to talk about flashover on high voltage commutators as being very destructive. The low voltage series DC used in EVs might not be the same problem ?
iMiEV MY12     105,131km in pure Electric and loving it !

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Soapbox on regenerative braking

Post by Squiggles » Sun, 21 Jun 2009, 06:11

The voltages& currents on a 500kW motor would have to be massive.
Considering the environment loco traction motors have to work in I would expect AC to be far superior.
Significantly they don't have much concern about weight, so they aren't looking for compact size Image

Attempts have been made at using regen braking on electric trains and pumping the energy back into the system. Very limited success but this is related to the infrastructure rather than the regen technology itself. So even in electric trains they just dump it into resistors.

Until recently Sydney electric trains used DC traction. I am not 100% sure but I think the Tangara was the first to use AC. Definitely AC on the Millennium, the harmonics from the VF drives played havoc with the system.
The DC trains had regen braking with resistive loads, I don't know anything about the motors though. Somebody out their must.

User avatar
coulomb
Site Admin
Posts: 3718
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Soapbox on regenerative braking

Post by coulomb » Sun, 21 Jun 2009, 07:13

I think around 2003 there was only one AC Tangara in the NSW fleet, and it happens to be the one involved in the Waterfall disaster. They were using all DC, and decided to get one AC as a trial. The hardware was cleared by the enquiry, so it was probably just a big fluke that the only AC train out of about 15 was the one that crashed. But I think it put back the AC acquisition for a long time. (Edit: per the Wikipedia Tangara page, it seems there have been no more AC Tangaras.)

The NSW system suffers from a 1500 VDC system. It may be difficult to regen back into that system. I'm pretty sure the Queensland electrics are all AC induction motors (25 kVAC system), and regen routinely.
Last edited by coulomb on Sat, 20 Jun 2009, 21:23, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Soapbox on regenerative braking

Post by Johny » Sun, 21 Jun 2009, 14:50

30 odd years ago I was part of a small team that rewired two Locos used by APM in the Latrobe valley. We replaced all the fabric covered wiring with "modern" insulation wires. They were Sepex DC with extremely large field resisters mounted out side that could be switched in with various combinations. (I got the Amp meters round the wrong way in BOTH Locos)
They were mainly used for low speed shunting and had no regen braking (as far as I can remember).

Edit: meters
Last edited by Johny on Sun, 21 Jun 2009, 04:50, edited 1 time in total.

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Soapbox on regenerative braking

Post by Squiggles » Sun, 21 Jun 2009, 15:34

coulomb wrote:
The NSW system suffers from a 1500 VDC system. It may be difficult to regen back into that system. I'm pretty sure the Queensland electrics are all AC induction motors (25 kVAC system), and regen routinely.


The biggest problem with 1500VDC is the the large currents the system has to carry. 600A+ for accelerating trains.
The regen problem is not so much getting back onto the 1500 system, it is the nature of the system layout. It is configured into a large number of sections, each isolated from the next. So unless there is another train in the same electrical section that is under load there is nowhere for the regen energy to go. To get any use out of the regen capacity of the trains thumping great big synchronised inverters would have to be installed in the traction substations so the energy could be fed back onto the HV AC distribution system.

I believe it would be easier with AC. There would still be the issue that each section of traction supply is actually single phase and the trains would need synchronised inverters.

Goombi
Senior Member
Posts: 532
Joined: Sun, 10 Aug 2008, 17:59
Real Name: Eugen
Location: Gympie

Soapbox on regenerative braking

Post by Goombi » Sun, 21 Jun 2009, 16:07

Still playing with trains? There is a bit of a child in all of us.. Image

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Soapbox on regenerative braking

Post by Squiggles » Sun, 21 Jun 2009, 16:35

Yep, spent 3 years building trains, then for the last 3 years been building tracks :). Problem is they won't let me play with the controls, they carry on with some rubbish about putting thousands of people at risk....as if!

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Soapbox on regenerative braking

Post by acmotor » Sat, 27 Jun 2009, 07:32

Hey guys,
The Chinese have the solution to regen braking resistor for when the battery pack is full.

Chinese power authority load bank....
Image

I recon this one would be good for 500kW continuous.
No one else in my vehicle appreciated my interest in the trailer mounted unit !
Image
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
coulomb
Site Admin
Posts: 3718
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Soapbox on regenerative braking

Post by coulomb » Sun, 12 Jul 2009, 05:34

A little more on regen with series motors here:

http://www.diyelectriccar.com/forums/sh ... stcount=40

"You've been around EVs long enough to know that doing regen with a series dc motor - without blowing up the motor, battery pack or controller, that is - will take something just shy of a miracle to pull off.

"My understanding is that if your motor is not neutrally timed with interpoles then you can pretty much forget it, no matter how fast and well-compensated the feedback loop inside the controller is. I intend to find out, though, as this seems to be one of those things that if you ask 5 different engineers about you get 6 different answers... Image "

Part of this large thread on a DC controller:

http://www.diyelectriccar.com/forums/sh ... 29062.html
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Goombi
Senior Member
Posts: 532
Joined: Sun, 10 Aug 2008, 17:59
Real Name: Eugen
Location: Gympie

Soapbox on regenerative braking

Post by Goombi » Sun, 12 Jul 2009, 05:47

We are not talking about DC F SERIES motor for REGEN
Please check the information. The word SEPARATELY has to be included..
Then you can ask 10 engineers and they will come with the same answer.

antiscab
Senior Member
Posts: 2436
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Soapbox on regenerative braking

Post by antiscab » Mon, 13 Jul 2009, 06:33

Goombi wrote: The word SEPARATELY has to be included..
Then you can ask 10 engineers and they will come with the same answer.


Because they cant be bothered explaining to you how to make it work reliabley without you blowing something up.

Yes you can get regen with series wound DC motors with interpoles, however the results are rather un-inspiring for the amount of bother involved.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Soapbox on regenerative braking

Post by Nevilleh » Sat, 18 Jul 2009, 01:06

I think that if you are stuck with a series wound dc motor, the only way to do regen with any sort of hope of success, is to drive an alternator with it! You can modify the regulator to produce enough voltage to charge the main battery pack and stick as much current into it as your - inevitable - belt drive can handle in terms of power. Probably about 4 kW, so that's as much regen as you can do easily. Still useful and reasonably reliable.

BjBlaster
Groupie
Posts: 65
Joined: Mon, 07 May 2007, 06:44
Real Name: Beau Walker
Location: Australia
Contact:

Soapbox on regenerative braking

Post by BjBlaster » Mon, 20 Jul 2009, 20:18

I never really thought about this until now, but how does an AC induction motor actually do regen? Does it have to have some sort of "back emf" or do you excite one of the other phase windings to get a magnetic field to generate power with? I have seen many people modifying the rotor to except perm magnets when they convert induction motors to generators for wind turbines so they don't have to excite a field winding. I'm assuming there are only 4 wires (3 phases and a neutral) going to the motor?

The VFD must do some fancy switching to suck that juice out of the wheels.... and how to you dump it somewhere else when the battery is full? Does the VFD have other outputs? Anyway I was just wondering as I haven't had much to do with industrial motors and wiring configurations and it sounds like those who have done this know what they're doing!
Last edited by BjBlaster on Mon, 20 Jul 2009, 10:20, edited 1 time in total.
If it's stuck, force it. If it breaks it needed replacing anyway - bj's shed

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Soapbox on regenerative braking

Post by Johny » Mon, 20 Jul 2009, 20:41

Someone is no doubt going to give you a better, more refined answer to this but this is my simplification.
You do not need a VFD to use an AC Induction Motor as a generator. The VFD merely allows you to control it easily.

Firstly, the rotor of an ACIM gets magnetised by the field in the stator coils.
Once the rotor is magnetised (fractions of a second to a couple of seconds depending on motor size) - If the motor is going SLOWER than the 3 phase field is rotating, then the motor acts as a motor.
If the motor is going FASTER than the 3 phase field is rotating, then the motor acts as a generator.

Edit: VFD not VDS
Last edited by Johny on Mon, 20 Jul 2009, 10:46, edited 1 time in total.

User avatar
coulomb
Site Admin
Posts: 3718
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Soapbox on regenerative braking

Post by coulomb » Mon, 20 Jul 2009, 21:55

BjBlaster wrote: how does an AC induction motor actually do regen? Does it have to have some sort of "back emf"
Yes, almost (?) all motors have back emf, and induction motors certainly do. You always regen from drive (never start generating from stop), so I believe the rotor is already magnetised, as Johny stated.
or do you excite one of the other phase windings to get a magnetic field to generate power with?
No, nothing like that, you just change the slip from positive to negative (depending on how you define the slip). It's all very natural.
I'm assuming there are only 4 wires (3 phases and a neutral) going to the motor?
3, actually; even in star configuration (but most larger motors are wired in delta), the neutral is not used.
The VFD must do some fancy switching to suck that juice out of the wheels....
No, nothing fancy, at least nothing more fancy that what it is already doing for motoring.
and how to you dump it somewhere else when the battery is full?
Ah, good question. Many industrial drives have a brake chopper; basically, there are terminals for a large wattage resistor that can take the regen energy if there isn't another motor that can take it (and there won't be in a typical EV). Basically, it just watches the DC bus voltage, and if it exceeds a certain value, it starts the brake chopper to try to bleed the voltage down again.

The slightly contentious issue is: does an AC EV need one of these for safety? I've changed my mind a few times on this, and at present I'm hoping that we can get away without it. Most of the time, the battery will be able to take regen, but of course that's not a reason to not do it if it's needed for safety. I think it should be possible to just tell the controller not to regen if the bus/pack voltage is too high, and arrange for the mechanical brakes to seamlessly take up the load.
Does the VFD have other outputs?
A typical VFD has 3 line inputs, 3 motor outputs, DC bus input/output, and a brake resistor terminal. Those are the only high current outputs. Most of them will have ports for turning on contactors and alarms, etc, as well as general purpose inputs for things like neutral switch, reversing switch, etc.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Goombi
Senior Member
Posts: 532
Joined: Sun, 10 Aug 2008, 17:59
Real Name: Eugen
Location: Gympie

Soapbox on regenerative braking

Post by Goombi » Mon, 20 Jul 2009, 22:07

AC and REGEN   This was suppose to be easy--Problem with converting instantly 360volt AC to 100 volt DC?/?? Please re-visit DC separately motor plus Regen....
The more we whip the cream --the harder it gets

BjBlaster
Groupie
Posts: 65
Joined: Mon, 07 May 2007, 06:44
Real Name: Beau Walker
Location: Australia
Contact:

Soapbox on regenerative braking

Post by BjBlaster » Mon, 20 Jul 2009, 22:08

Nicely answered. No wonder you guys are attracted to this as a drive system. It's very versatile :)
If it's stuck, force it. If it breaks it needed replacing anyway - bj's shed

zeva
Senior Member
Posts: 422
Joined: Sat, 15 Dec 2007, 05:09
Real Name: Ian Hooper
Location: Australia
MSN: sigmunky@hotmail.com
Contact:

Soapbox on regenerative braking

Post by zeva » Mon, 20 Jul 2009, 23:31

coulomb's on the money.

To clarify the need for rotor excitation, basically the VFD drives the motor as normal but targetting a speed X rpm slower than its current RPM (X being negative slip). Due to the voltage/frequency ratio with induction motors, this means the driving voltage is lower than the rotor's back-EMF, so current flows backwards.

It's almost identical in principle to regen with a commutated DC motor (driving voltage lower than back-EMF resulting in reverse current flow), except that the controller has to keep rotating the field slightly slower than the rotor to ensure back-EMF remains higher than driving voltage. Hmm not sure if that makes things any clearer actually?!
Ian Hooper
--
"Never doubt that the work of a small group of thoughtful, committed citizens can change the world." - Margaret Mead
http://www.zeva.com.au

zeva
Senior Member
Posts: 422
Joined: Sat, 15 Dec 2007, 05:09
Real Name: Ian Hooper
Location: Australia
MSN: sigmunky@hotmail.com
Contact:

Soapbox on regenerative braking

Post by zeva » Mon, 20 Jul 2009, 23:40

PS: Coulomb, I reckon a big shunt for dissipating regen energy is useful even when the batteries are happily accepting a charge.

ThunderSkys etc can only take about 1C charge current which doesn't represent a huge amount of regen braking force. But it's still better to slow a vehicle down with a motor than with friction brakes since there's nothing to wear out in an (induction / PMSM) motor. So you might as well maximise regen and have a big shunt resistor to bleed off excess power as heat? My 2 cents..
Ian Hooper
--
"Never doubt that the work of a small group of thoughtful, committed citizens can change the world." - Margaret Mead
http://www.zeva.com.au

Post Reply