What motors will I require for a constant 120kW equivelant output?

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T1 Terry
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What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Mon, 28 May 2018, 11:01

I am looking seriously at developing my big bus project into a diesel generator/ electric drive project. I want to mount the diesel engine and generator as a separate item and in a different location to the electric drive motors and use a large battery bank as the buffer between supply and demand. The project will have a 4 speed Alison automatic transmission and a peak 4,000 rpm would be heaps, although the added torque would probably allow this to be even lower as the revving out before changing up to the next gear would not be a requirement anymore.
The original 500 Bedford diesel could produce up to 205hp in the turbo charged form but a realistic 150hp was best for keeping all the bits inside the cases, so a constant 120kW and peak of maybe 200kW would be the aim I think. No idea how to convert this to the output from an AC electric motor using a VFD so I'm looking for guidance from the collective wisdom on this forum. My main concern is heat so I doubt the air cooled rewound 48v motor I have could handle it and I have no idea of the capabilities of the EVO axial flux motor I have, but I doubt it could do the job on its own.

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Re: What motors will I require for a constant 120kW equivelant output?

Post by jonescg » Mon, 28 May 2018, 11:28

Hi Terry, the Evo motor you have will put out 90 kW all day long, and it's definitely capable of peaks of 175 kW (we dyno'd the race bike at 175 kW - 230 hp- to the ground). With a 720 V DC beak bus voltage you might even get this up to 190 kW.

I don't know about running the electric drive through the automatic transmission - pretty sure it's been done before but probably a bit lossy. But the diesel engine would certainly be able to keep the battery topped up much like a BMW i3 range extender. At a highway speed cruise the bus might only consume 40 kW, so the ICE need not deliver more than about 20 kW to the battery to keep things ticking along.
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Re: What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Mon, 28 May 2018, 12:03

Thanks Chris. I wonder how long it could deliver the 120kW before problems started to occur and would a temp sensor in the coolant outlet be a good indicator? I could do the 720vdc using the monster VFD I bought from Weber and Coulomb that wasn't suitable for the MX5 project but it is only air cooled where the Wavesculptor VFD is cooled via a coolant heat transfer method much like the EVO motor.
As far as the auto, I would do away with the torque converter and drive the input shaft and oil pump direct with an additional oil pump to hold the oil pressure up when stopped at the lights etc. the other option is to have a special fluid coupling made but I can't see any value in having the motor still spinning when the vehicle isn't moving ... unless it would help with cooling?

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Re: What motors will I require for a constant 120kW equivelant output?

Post by Richo » Mon, 28 May 2018, 12:56

Hmm that's like about a 75kW 4-pole induction motor.
75kW 1,500RPM
120kW 2,400RPM
200kW 4,000RPM (assuming voltage high enough)

If you ran the rewind so the voltage peaks out at 2,400RPM (~250VAC) would be about right.
You could still reach 200kW+ at 2,400RPM but still run at higher RPM with reduced torque.
Still that's a 500kg+ motor...

Not too sure if that is really realistic.
When the bus is cruising along say at 80kph what would RPM be?
How much does the original ICE motor weigh?
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Re: What motors will I require for a constant 120kW equivelant output?

Post by jonescg » Mon, 28 May 2018, 13:00

You won't want the motor to turn for no good reason, and the stator is cooled from behind so there's no cooling benefits to having it turn over.

The motor windings will tolerate being at 130'C but you don't want to be there for very long. Make sure the radiator is sufficiently sized to shed the heat and keep the flow at or above 8 l/min. The AFM140 was designed for a hybrid bus, so it's only right that someone actually use it for that :D
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Re: What motors will I require for a constant 120kW equivelant output?

Post by Richo » Mon, 28 May 2018, 13:03

What motor do you have now?
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Re: What motors will I require for a constant 120kW equivelant output?

Post by Richo » Mon, 28 May 2018, 13:06

jonescg wrote:
Mon, 28 May 2018, 13:00
The AFM140 was designed for a hybrid bus
Should I ask what they cost?
Are they available for the general public to buy these days?
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Re: What motors will I require for a constant 120kW equivelant output?

Post by jonescg » Mon, 28 May 2018, 13:15

I paid $12,000 for mine. Phi381 motors are about the same price nowadays - 38 kg and 90 kW all day. 200 kW peak.
Terry has one in his possession - you know what they say about a bird in the hand.
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Re: What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Mon, 28 May 2018, 14:37

Richo wrote:
Mon, 28 May 2018, 12:56
Hmm that's like about a 75kW 4-pole induction motor.
75kW 1,500RPM
120kW 2,400RPM
200kW 4,000RPM (assuming voltage high enough)

If you ran the rewind so the voltage peaks out at 2,400RPM (~250VAC) would be about right.
You could still reach 200kW+ at 2,400RPM but still run at higher RPM with reduced torque.
Still that's a 500kg+ motor...

Not too sure if that is really realistic.
When the bus is cruising along say at 80kph what would RPM be?
How much does the original ICE motor weigh?
Original motor was front mount and would have been over 700kg dry, add the 4 core radiator, coolant and 12 ltrs of oil, huge flywheel and cast iron bellhousing and I doubt it would have been much under 1 tonne we took out. So we have a bit to play with when it comes to batteries, a motor and a controller and still be able to carry the 3 cyl Perkins and generator in the rear. The plan is to mid mount the electric motor, I had already installed a rear mount 351 Ford Cleveland V8 rear mounted and planned to run it on LPG but the price of Autogas has now put that out of the question and my long term aim to build an electric drive bus has had another chance to actually happen.
As far as 80km/h, I'm old but not that old :lol: Although a heavy vehicle it is limited to 100km/h it would be nice to have a bit to spare for overtaking so I don't have to spend too long on the wrong side of the road. The original engine maxed out around 3,000rpm but could just maintain 100km/h on a flat or slightly down hill road with a good tailwind :lol:

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Re: What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Mon, 28 May 2018, 14:40

jonescg wrote:
Mon, 28 May 2018, 13:00
You won't want the motor to turn for no good reason, and the stator is cooled from behind so there's no cooling benefits to having it turn over.

The motor windings will tolerate being at 130'C but you don't want to be there for very long. Make sure the radiator is sufficiently sized to shed the heat and keep the flow at or above 8 l/min. The AFM140 was designed for a hybrid bus, so it's only right that someone actually use it for that :D
Is the motor I have an AFM140? It's in a wooden box in the workshop with the other 48v motor on top of it in another box and then the big VFD in another box on top of that, so actually eyeballing it will require a bit of crane work.

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Re: What motors will I require for a constant 120kW equivelant output?

Post by jonescg » Mon, 28 May 2018, 15:59

Did you buy it from Ben? I think that was the AFM140. If it's the 4-turn motor you can run it on a bus up to 800 V DC. If it's the 3-turn motor, you can probably use a 700 V bus but no need for field weakening. It will be fast enough.
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Re: What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Tue, 29 May 2018, 09:35

jonescg wrote:
Mon, 28 May 2018, 15:59
Did you buy it from Ben? I think that was the AFM140. If it's the 4-turn motor you can run it on a bus up to 800 V DC. If it's the 3-turn motor, you can probably use a 700 V bus but no need for field weakening. It will be fast enough.
Yes, this was part of the package I bought from Ben, along with the Wavesculptor controller that the whole package had been tuned together in Brisbane by Tritium who build the Wavesculptor VFD. I was keen to run this as a package because it was already set up to go but if the motor really requires the higher voltage then it will need the monster VFD we bought of Weber and Coulomb as it has the 720vdc upper limit from memory.

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Re: What motors will I require for a constant 120kW equivelant output?

Post by Richo » Tue, 29 May 2018, 12:34

jonescg wrote:
Mon, 28 May 2018, 13:15
I paid $12,000 for mine.
Ouch
$2,000 in material
$2,000 in profit
$8,000 in R4ping
But I'm sure it's still worth every $
Given the 500kg+ blob alternative :lol: I'd do the same.
jonescg wrote:
Mon, 28 May 2018, 13:15
you know what they say about a bird in the hand.
Not as good as one in the oven :lol:
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Re: What motors will I require for a constant 120kW equivelant output?

Post by Richo » Tue, 29 May 2018, 12:42

T1 Terry wrote:
Mon, 28 May 2018, 14:37
I'm old but not that old :lol:
Nah it's just continuous power is directly related to RPM.
I find most vehicles have changed into final drive by 80 unless under acceleration.
Either way since you have one of those motors with magnets in it the point is moot.
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Re: What motors will I require for a constant 120kW equivelant output?

Post by reecho » Tue, 29 May 2018, 20:16

Running an Allison AT540 or similar?. No lockup clutch so plenty of slip. I would avoid. Whats the diff ratio?. Might be low enough for direct drive?

I used to rebuild Allison transmissions a few years back. Mainly World Series.

Allison started making hybrid drive transmissions a few years back. Beautiful things. Basically a scaled up Prius drive.... :-)

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Re: What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Wed, 30 May 2018, 10:32

reecho wrote:
Tue, 29 May 2018, 20:16
Running an Allison AT540 or similar?. No lockup clutch so plenty of slip. I would avoid. Whats the diff ratio?. Might be low enough for direct drive?

I used to rebuild Allison transmissions a few years back. Mainly World Series.

Allison started making hybrid drive transmissions a few years back. Beautiful things. Basically a scaled up Prius drive.... :-)
I did think about the Hybrid Drive Alison, but they are mainly for take off assist and it would still require the rear engine or a mid mount engine and I'm shying away from either of those choices.
As far as the AT540, the torque converter will be replaced with a direct drive coupling for the input shaft and oil pump with a supplementary pump to maintain oil pressure when the main pump is not being driven.
As you are experienced with the AT540, do you think it will handle the torque of the axial flux motor? I heard talk about issues with tearing the centre mount section loose in the case, is this really an issue? As far as locking in each gear, does that require the mod to allow pressure to be redirected via a solenoid and hoses externally mounted to stop automatic upshifting?

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Re: What motors will I require for a constant 120kW equivelant output?

Post by reecho » Thu, 31 May 2018, 15:13

How much does this bus weigh? Did it come with an AT540 from new?

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Re: What motors will I require for a constant 120kW equivelant output?

Post by T1 Terry » Fri, 01 Jun 2018, 19:14

My guess would be under 10tonne fully loaded with full tanks, possibly a lot lighter. It had a 5sp manual box bolted to the original 500 Bedford diesel engine, can't remember the diff ratio but I completely renewed the diff assembly including the hemisphere because the planetary gears had machined themselves 2 thrust washers deep into the cast iron and the crown wheel was so worn it was near knife edge.
The AT540 was from a wreckers so I have no idea what size truck it came out of to gauge if it handled a load that size or not. When I worked for Western Road Bus Service we replaced the tied diesel engine with 351 Ford Cleveland engines running on LPG and new AT540 Alison transmissions and they performed faultlessly, but I'd imagine the low down torque from this axial flux motor would be higher than the low down torque of a Ford 351.

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