# Diesel electric driveline using leaf em57



## remy_martian (Feb 4, 2019)

If this was your goal, full stop:

"This is for a boat propulsion test project so we can be more flexible with diesel engine and transmission placement"

You could eliminate 90% of the stuff in your diagram and simply run an EM57 on the diesel as a generator, thru some contactors to get reverse and neutral, then to an EM57 on the prop drive. No inverters, controllers, etc.

You need to realize that marine runs at high continuous power ratings and that almost all automotive motors will run continuous at around 20-30% of rated power. You may not be able to cool the motors with the output a marine 6BT makes.


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## tumnahi232 (2 mo ago)

Are these motors more likely to be available because Nissan didn't build coolers into the battery packs? (Cost of replacing batteries meaning car is written off earlier as a non-economic fix?)


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## brian_ (Feb 7, 2017)

tumnahi232 said:


> Are these motors more likely to be available because Nissan didn't build coolers into the battery packs? (Cost of replacing batteries meaning car is written off earlier as a non-economic fix?)


I think that in any EV the motor will outlast the battery, the inverter, and every chassis component... so EV motors (with transaxles) in general should be relatively available in salvage. Any advantage in availability of the Leaf motors is likely just due to the length of time that they have been in production and the number of units produce.

Leaf motors also have an advantage over most EV motors unrelated to availability: they unbolt from the transaxle for relatively easy use in other applications compared to typical motors with housings integrated with the transaxle.


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## ghouighyte (2 mo ago)

yep,all those factors are the reason we want to go with Leafs for this project. easy to get in North america, cheap, availability of VCU that is pretty easy to use. we plan to have a full spare em57 and inverter on board as a spare, two people could easily do a motor swap if need be at sea. 

@remy, i never thought of that idea but it would simplify things. Essentially the em57 would just become a 3 phase generator end. do you know how much current and voltage it would output? And wouldnt i need some sort of controller for the motor? 

regarding the 6Bt it is rated at 210hp 2600RPM - according to curve charts gets about 700NM at 1800RPM - so ya its a considerable amount of power driving that em57. not sure what the limits are, like i said, we would have external 12 volt pumps feeding marine grade heat exchangers we could use for the coolant of the em57. But not sure if that will be enough...i guess we will find out.


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## brian_ (Feb 7, 2017)

The entire operating speed range of a marine 6BT is within the speed range that the EM57 is limited by current (and thus torque), not power. The engine's torque output is far too much for the Leaf motor, unless you severely limit the engine.


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## brian_ (Feb 7, 2017)

ghouighyte said:


> ... Essentially the em57 would just become a 3 phase generator end. do you know how much current and voltage it would output? And wouldnt i need some sort of controller for the motor?


The EM57 on each engine would be a 3 phase generator in any case; the suggestion was to transfer the power from generator to motor directly, rather than rectifying and re-inverting it. The suggestion was apparently to operate motor pairs running in synch with each other, so the motor would not have a controller, and would turn at the same rate as the generator (because it turns in synch with the phase of the power). This wouldn't work in a road vehicle, but could possibly work to drive a propeller. It would have no advantage over a simple shaft, other than flexibility in routing wires rather than a rigid shaft.


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## ghouighyte (2 mo ago)

ok, interesting, that would still be an advantage in this scenario as engine placement is key. we want to put them in a new aft engine room, as opposed to the midship, so they are much more friendly to maintain. 

With regards to the 6BT being too much torque, do you guys know what the limit would be for input torque to an em57 if it were to be used as a generator?. From my understanding, the continuous torque is like 320NM from 1-3500RPM or so when used a motor. Thats based on using a gen3 inverter. wouldnt it be the same if it were driven by something else? I could always use smaller engines and use more of them. We havent purchased engines yet.


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## remy_martian (Feb 4, 2019)

Your problem is that marine diesel puts out too much _continuous_ power and the EM57 numbers you are using are peak power ratings, not continuous ones. A car only needs about 20kW of continuous power on the highway, whereas your marine application will easily run 5-7x that.

Yes, you can gang motors and generators, but your reliability gets compromised.

If anyone knows the max continous power an EM57 can do, it's @Dala, so this posting will hopefully summon him into the thread.


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## brian_ (Feb 7, 2017)

ghouighyte said:


> I could always use smaller engines and use more of them. We havent purchased engines yet.


That would help at the engine-generator end, but what about the motor-propeller end? If each prop really needs the power of a 6BT, a Leaf motor won't do.


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## ghouighyte (2 mo ago)

based on the calculations, the boat needs about 2x110KW to go hull speed of 10.6 knots. This is the max target speed. in most cases it will be about 7 knots for most economical cruise speed and this would take about 2x35KW. 6BT was recommended based on its size, weight, reliability, and parts availability, but probably is a bit over powered. I was hoping to experiment with 1 em57 with gen3 inverter an TS VCU and see if it could turn the marine gearbox input shaft. But we can also split them up just like the generators install another pair of drives (saildrive) and have 4 motors total - 1 shaft drive and 1 saildrive on each side, or 4 saildrives - each saildrive is rated 58 KW at 3200 RPM - probably could handle a bit more.


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## remy_martian (Feb 4, 2019)

afaik, 58kW per drive should be ok on the motor side, though you'll probably need a gear reducer on each motor to pull it off at 3200 RPM without smoking the windings. Most drives have speed reducers in them, but I don't know of any that'll go to 10kRPM.

This Leaf motor business gets ugly (expensive) real fast when you start going beyond the "all ya gotta do" Powerpoint slides. Coupling, gear drives, speed reducers/boosters, clustering multiple generators. Yikes! Maybe you should consider hydrostatics?


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## ghouighyte (2 mo ago)

forgot to mention the saildrives do have a gear reduction of 2.49:1 and they are also reversing gear as well.

i remember reading some info out there on the em57 continuous i kept on reading the "80kw continuous" figure.- i searched again and found a post on this forum about some of the data - Leaf Motor - Peak Power? 

though i believe it refers to the gen 1 em57

in my case, for the drive motors, I would be trying to run at highest torque possible from 1-1300RPM


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## brian_ (Feb 7, 2017)

ghouighyte said:


> based on the calculations, the boat needs about 2x110KW to go hull speed of 10.6 knots. This is the max target speed. in most cases it will be about 7 knots for most economical cruise speed and this would take about 2x35KW. 6BT was recommended based on its size, weight, reliability, and parts availability, but probably is a bit over powered. I was hoping to experiment with 1 em57 with gen3 inverter an TS VCU and see if it could turn the marine gearbox input shaft. But we can also split them up just like the generators install another pair of drives (saildrive) and have 4 motors total - 1 shaft drive and 1 saildrive on each side, or 4 saildrives - each saildrive is rated 58 KW at 3200 RPM - probably could handle a bit more.


Based on the 2 x 110 kW requirement for hull speed, the 6BT choice is understandable, but maintaining that speed with two Leaf motors seems unreasonable, so using saildrives as well might be necessary. Economical cruise at 2 x 35 kW would be within the power capability of two Leaf motors driving the props and two Leaf motors as generators, but the generators may be beyond their torque ratings due to the low speed if directly coupled to those engines.

The generators would be happier if driven at some multiple of the engine speed, but of course it would be desirable to avoid the mechanical drive (by gears, chain, or belt) that would be required for that.

Keep in mind that mechanical power is torque multiplied by shaft speed, so with limited motor or generator torque lower speed means proportionately lower possible power.


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## brian_ (Feb 7, 2017)

ghouighyte said:


> i remember reading some info out there on the em57 continuous i kept on reading the "80kw continuous" figure.- i searched again and found a post on this forum about some of the data - Leaf Motor - Peak Power?
> 
> though i believe it refers to the gen 1 em57
> 
> in my case, for the drive motors, I would be trying to run at highest torque possible from 1-1300RPM


On page 12 of the presentation linked in that discussion it is noted that the Leaf motor is


> "Capable of operating at 80 kW continuously at 7,000 rpm with stator temperatures leveling out at about 135 C"


however, that corresponds to only 109 Nm. The same power at lower speed means higher torque and overheating.

The peak torque listed in that document is 280 Nm, which is the typical Leaf spec, and is the limiting factor at low speed... and even that is not sustainable continuously. As speed increases, 280 Nm corresponds to 80 kW at 2728 RPM, so if 80 kW is the power limit then torque drop off above that point.

The effective power limit for a Leaf, once above the range in which torque is limiting, is not the motor. The inverter can be a physical limitation, and is normally a programmed limiter, to protect the battery from excessive discharge rate. This is why essentially the same motor has a peak power limit of 80 kW (with 24 kWh and 30 kWh batteries), or 110 kW (with 40 kWh battery), or 160 kW (with 62 kWh battery).

At 1300 RPM 280 Nm would be 38 kW, and that would still be a peak power that could not be sustained.


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## remy_martian (Feb 4, 2019)

Reader's digest version: you need a gearbox both on the generator and the motor that is sized for the power you are putting through it.


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## ghouighyte (2 mo ago)

thanks for the info guys, its always a fun learning process. i think going with multiple low power saildrives would be a better and safer option for the em57. 

as far as a DC generator - ive read that the UQM220 has a generator feature in the native SW, and ive seen it deployed as a generator on some new production boats, But not sure the continuous output..one of the datasheets says 150ADC, im assuming at 360VDC. it has a continuous rating of 120KW and 300NM. though tough to find info as uqm is no more..


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