Any ideas for large motor, and electronics

Hi,

As some of you may know, I'm building a model submarine.

It will be huge with a displacement of around 500kg and a length of 4m. Having worked out a rough idea as to the size of the motor required, 3hp. I'm now looking for suggestions. Sites like technobots don't stock ones large enough and so I'm struggling to find an answer. Then there is the matter of how to control the speed. Ideally I'd like proportional control.

So, does anyone know where I can find a motor, ideally with the electronics to control it? The onboard power will be provided for by two 12V batteries, of which the AH is still undecided.

Thanks

Michael

Reply to
Michael
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Think ..just guessing here the more hp required on a dc motor .........you end up going with more voltage...........like HP equals 36 volts dc............but you can get your 36 volts by coupling 3 batts together. but thats 1 horse. as in this motor for this golf kart...

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He also does 2.7 hp treadmills....bet they are DC.............ask him the voltage and if he sells the motors as separate items.

These will have speed controllers as well.

sorry I don't know the cheap route.

all the best..mark

Reply to
mark

We have done chargers for two large underwater devices, both of which are military in nature so I cannot give more details, but both used higher voltage batteries for propulsion, as the losses in using high-power 12V motors are just too large to ignore.

One had 110V nicads, which were later changed to Lithium-Ion, the other has Lithium-Ion to start with.

Controlling the motor with PWM is quite practical, and the current is much lower at 110V.

Moving 500kg through the water with 12V is almost a non-start I would have thought, as the battery capacity would have to be enormous to give you any length of operation.

Although 110V DC sounds a lot, it is very common on the railways for loco starting, substation switch tripping and so forth. You WILL need lots of cells though :-))

Coincidentally, we went to Royal Hallamshire Hospital in Sheffield yesterday to check over a couple of our 110V chargers in the power room that we supplied new in about 1997. The batteries should have been changed after 5 years, but nobody had thought about testing/checking, so when they had a power failure recently, the main breakers failed to trip out and the standby genny wouldn't come on-line.

Red faces all round, and an urgent call to us about new batteries and a charger check.

Charger was fine, the batteries were unbelievably bad. All the cases had split open, in the worst cases they had sections of the casing off, exposing the plates etc inside. These were Sonnenschien Powerfit batteries so not exactly a crap brand. If I get a minute during the week I'll take some pictures of the batteries before they go for disposal.

The hospital guys fitted the batteries that we shipped up to them, and we checked both chargers which were operating OK.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

Michael

It might be worth contacting companies like Parkside Electronics, who sell batteries, motors and controllers for electic model locomotives. They often advertise in Model Engineer. 3hp is a rather large motor, so I don't know if they do anything that powerful. However, if they don't, I suspect they might know people who can help. Their details are:

Parkside Electronics Unit 2E & 3J, Valley Mills Southfield street Nelson Lancs BB9 0LD

01282 613646 snipped-for-privacy@btinternet.com

Also, another company offering similar products is 4QD

30 Reach Road Burwell Cambridge CB5 0AH 01638 741930
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Hope this helps

Alastair

Reply to
Alastair

Hi Michael,

You might find it interesting to consider a mains 3 phase motor.

Before you delete this reply as a bit wacky, please read on.

Motor inverters are quite cheap now especially secondhand on ebay. All of these rectify the mains to form a DC source from which variable frequency 3 phase AC is synthesised by electronic switches. I would think it possible to have a high voltage battery ( much more efficient at these powers than low voltages and huge current draw) and feed this in the AC inputs to the rectifiers in the inverter. Most of the inverters can be controlled by buttons on the module, remoted switches and knobs or by RS232/485 digital commands from a microprocessor. This may be a bit exotic for your project and maybe a skills mismatch but I'll throw it in as an idea.

It is *just *possible that I can get hold of programming info for Siemens Micromaster inverters as someone I work with used to work for Siemens Automation and Drives.

Good Luck

Bob

Reply to
Bob Minchin

Hi Peter, you should have called round for a coffee or tea, sounds about par for the course. I used to work for a university, with a very similar name!!! They also had UPS problems, and decided that perhaps burying ones head would solve the problem. I picked up some of the pieces, but finally decided I had, had enough and left. Try getting a crisis management decision during a crisis...

Cheers

Joules

Reply to
Joules

--You might want to follow what some of the larger weight class battlebots are using. IIRC the best motors, in terms of torque, efficiency, etc are still made my Lemco, which is a UK based company. Also, the price of lithium-ion batteries is finally starting to drop; they're better than NiMH I'm told..

Reply to
steamer

electronics

Look for a permanent magnet DC servo motor. There are quite a few up to 1 HP - maybe ganging them is a possibility. Here is a half horsepower motor just as an example off ebay:

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Altenatively look for smallish bettery powered vehicles - for instance I have a little Harbuilt 660 flat bed factory trolley that has a 24v DC motor that must be arround 3 HP. Milk floats are another possibility but are usually 72v

AWEM

Reply to
Andrew Mawson

Li-Ion are still way ahead on price, even with the reductions of late, but longer-term they will become competitive once the volumes rise. As the main makers are AEA Technology and Sony, and as AEA still hold the master patent (I believe) there is some vested interests in keeping the price up.

When we did the underwater roving vehicle, it had four 110V Li-Ion batteries, made up of series/parallel cells, each charger channel (there were 4 channels) had an output of 50 Amps.....

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

Fork truck propulsion and hydralic pump motors are another possibility.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

Bob, Not being an EE but I was under the impression that yes invertors did change AC to DC , work the magic bits on it and then output 3~ but on a single phase one they took 240v AC and converted it to around 350v Dc then did the ear of bat, tongue of newt routine.

As I said I'm no EE but after picking a large board type invertor up after being switched off but before the caps had bled out I feel, nay insist, I'm right

Whilst trying to stuff both arms under my armpits, not drop the invertor and do the three shoe shuffle across a cluttered workshop..................................

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

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Reply to
John Stevenson

You might have to rethink you battery system but the chap on the site mentioned below imports some high quality electric motors from germany for building electrically assisted cycles with . Can supply controllers and power packs as well.

Might take some ingenuity to adapt to a submarine but not to difficult I would think. possibly cooling would be a problem if you wanted to run at continous rating as these motors are designed for the hub of a bicycle wheel.

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G.Harman

Reply to
g.harman

Its difficult to say this and please don't take this as a personal slight, but from what you posted the chargers are quite clearly not operating ok. There is an ongoing fundamental misunderstanding between battery manufacturers and battery charger manufacturers that has persisted for literally decades, the number of battery charger and battery manufacturers that actually understand charging properly, particularly with regard to anything other than lead acid wet cells are very few and far between.

With a particular battery manufacturer, using a correctly designed charger, observed (as opposed to predicted) cell life in float operation using VRLA cells now exceeds 35 years (recently discharge tested to confirm in excess of 90% original design capacity).

With a whole raft of other batteries (incorrectly designed/specified or constructed) coupled to a whole raft of seemingly correctly designed chargers (after being fed misinformation by the battery manufacturers they quite clearly aren't) a predicted service life of

15 years becomes an actual life of 3 - 5 years complete with casing splits and corrosion damage. A number of major plc's have experienced very severe problems with just such systems ongoing for many years. meanwhile the correctly designed and manufactured systems just sit there year after year without any concerns whatsoever.
Reply to
Mike

No comment.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

Hi Michael,

You might find it interesting to consider a mains 3 phase motor.

Before you delete this reply as a bit wacky, please read on.

Motor inverters are quite cheap now especially secondhand on ebay. All of these rectify the mains to form a DC source from which variable frequency 3 phase AC is synthesised by electronic switches. I would think it possible to have a high voltage battery ( much more efficient at these powers than low voltages and huge current draw) and feed this in the AC inputs to the rectifiers in the inverter. Most of the inverters can be controlled by buttons on the module, remoted switches and knobs or by RS232/485 digital commands from a microprocessor. This may be a bit exotic for your project and maybe a skills mismatch but I'll throw it in as an idea.

It is *just *possible that I can get hold of programming info for Siemens Micromaster inverters as someone I work with used to work for Siemens Automation and Drives.

Good Luck

Bob

Reply to
Bob Minchin

electronics

Erm -Dunno why this suddenly reposted itself. Apologies It won't let me delete it either!

Bob

Reply to
Bob Minchin

John, you paint a wonderful word picture!!

Yes inverters do normally take in AC but the first thing that happens is rectification to DC. Yes, peak dc volts will be root 2 x the AC voltage.

240Vac equates to 340Vdc but there is usually some tolerance before the inverter shuts down having sensed low voltage. I'd guess at 300v worth of batteries would possibly be acceptable. Yes these voltages bite the hand that touches them ( Thinks - Are high voltages female?) but the big advantage should be much lower operating currents (say 8 amps for 3 horses) as well as universally available motors. We all know the superb degree of control that 3 phase inverters bring to the party.

I'm off to the workshop to play and see what degree of variability a micromaster inverter will tolerate.

Will report back later.

Bob

Reply to
Bob Minchin

">240Vac equates to 340Vdc"

Are you sure, it felt like 350 VDc to me

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

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Reply to
John Stevenson

No John, you're getting over sensitive in your old age - it's ONLY

339.4112548 peak

AWEM

Reply to
Andrew Mawson

microprocessor.

OK here are the results from my experiments

Set up

ac mains into Variac Bridge rectifier on the output of the Variac DC terminals connected to 120uF 440V capacitor. (just happened to have this value to hand) Voltmeter connector across the capacitor. Input to 500watt Micromaster connected Positive to Line1 in, Negative to Neutral in.

3 phase 3/4 hp delta connected motor on output of inverter. Various earth bonding wires to taste. Thick soles sandals on concrete floor! Method Increasing variac output until 230 vdc is measured on the capacitor and the inverter switches on and runs motor OK checked at up to 100Hz output and rapid switching between CW and anti CW at 100Hz. with motor running or stopped, the DC input voltage can be reduced to 200vdc and the motor will operated as above. However, if the DC supply is removed to the inverter, it will not switch on until the voltage is raised to 230vdc once more.

Conclusion

A battery pack capable of delivering 230v at or near its end point will run a micromaster inverter satisfactorily So 230 Nicads or NiMh cells or about 80 Li-Ion cells should do the job. The fully charged voltage of these combinations will not exceed the max input of the inverter.

Regards

Bob

Reply to
Bob Minchin

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