anyone know how to cheaply run a large dc industrial motor?

Discussion in 'Propulsion' started by tugboat, Feb 12, 2010.

  1. tugboat

    tugboat Previous Member

    Hi--i dont know much about setting up a dc motor for propulsion but thought the motor below should be adequate for my need for torque for a small 29 ft tug.


    these are the specs on the motor id like to use...

    Used Electric Motor

    Used Imperial DC Electric Motor
    HP: 20
    Frame: 326AY
    Type: HS
    Wound: Shunt
    RPM: 1150
    Fld. Volts: 172
    Fld. Amps: 2.18
    Volt: 240
    Ins. Class: B
    Ser. # 365578
    Shaft Size: 1.910
    It was running very good when taken out of service
    625 Lb. 42 X 34 X 26 High



    my questions-

    1.- would it have more torque than say a golf cart motor of the same hp?

    2. this one stumps me- what controls do i need that i can get cheaply that would run F,n,r, and control the speed??

    3.Do i need a controller like a golf cart or EV uses?

    4. Would 28, 13 volt batts (car batts) give me enough power to run for at least an hour?

    5. i have no idea what amperage is needed for this motor any ideas on what it might need to control the speed?

    the plan-

    My plan was to use a diesel genset @ 5000 watts to run this motor since it has a 220 volt outlet. and use the genset at the same time to charge my battery bank while the boat is moving.

    the 120 volt sockets are used to run a 100 amp charger. which in turn charges the batts -

    or the other option being that the gen runs a small 120v ac motor which turns two truck alternators which charges the batteries?

    while the batts are charging i am hoping to run the 220 volt 20 hp engine using the same genset( as mentioned the one i have in mind is not large at 5000 watts and 10 hp diesel with two 120 v and one 220 volt socket)- im trying to keep weight and space down so a larger genset is not going to work.

    if you have any background in setting up industrial motors i would really like some help here...

    perhaps using two golf cart motors would provide the same power if geared to like 5:1????


    thanks
    Doug
     
  2. alan white
    Joined: Mar 2007
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    alan white Senior Member

    If 20 hp is your goal, you should look into the German Perm motor or try and find a Briggs and Stratton Etek motor. Both are very light (under 30 lbs) and controllers are easy to9 match to them. you can even get kits with motor, controller, and wiring harness.
    To charge batteries thru a genset and then use the batteries to run a motor is too roundabout and will waste energy in conversion by way of heat.
    There are better ways to do it.
    The question is, why aren't you using a 10 hp diesel to run the prop? The problem is the weight and complexity and cost of what you're proposing.
     
  3. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    1.- would it have more torque than say a golf cart motor of the same hp?
    Yes, considerably more.

    2. this one stumps me- what controls do i need that i can get cheaply that would run F,n,r, and control the speed??
    Reversing the field current changes direction. To control speed efficiently you need a pulse width modulating controller. I would design and build it myself because there are electrons running around my brain and I have time. Because of your questions I guess you can't.

    3.Do i need a controller like a golf cart or EV uses?
    That is already answered. A cheaper way would be a rotary switch selecting the desired number of batteries. The disadvantage is that the batteries will be unevenly discharged.

    4. Would 28, 13 volt batts (car batts) give me enough power to run for at least an hour?
    Assuming 80% efficiency you would need 17.5 kW/hour stored for 1 hour at full speed. 15 pieces with 100 Ah capacity can provide that.

    5. i have no idea what amperage is needed for this motor any ideas on what it might need to control the speed?
    60 Amps at full load.
     
  4. CaptBill
    Joined: Jan 2010
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    Location: Savannah,Ga

    CaptBill CaptBill

  5. tugboat

    tugboat Previous Member

    Thanks Alan- what i was thinking was simply using the batts for say an hour then running the genset to both charge and run the motor for an hour etc.. then go to batts again and so on.
    a ten hp diesel wouldnt even come close to the torque and direct reversing ability that a electric motor can. so i wanted an affordable alternative to expensive diesels...the engine im talking about--its 200 bucks! and it looks like its got the torque of a large diesel..from what i can tell. it weighs 650 lbs! has a 2 inch dia shaft! etc. very robust. i think that the setup of using a genset and batts is a standard D. E. system used on subs and tugs??
     
  6. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Your'e probably right, tugboat. I think I misunderstood the comment. Others would know more than I about tugs.
     
  7. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    20hP = ~15kW @ 240V ~ 60Amp

    Tug Boat, Stick to diesel. That electric motor is going to cost a fortune in batteries and charge power.

    To run such a motor off batteries you will need about 15 000 AH batteries. If you want any kind of life out of your batteries (x4) you will need AT LEAST ! 60 000AH batteries to run it for an hour at a time.

    If that battery is 240V DC and you're stacking the batteries you will need 20 stacks.

    20 batteries, 12V, 120AH in series will give you 240V DC x 120AH of which you can use 25% at a time if you expect some life span from that stack so it means you have a 30 to 40AH stack. Go figure. Also batteries does not like to be charged in series, the better ones and weaker ones get overcharged and undercharged.

    Not worth it !
     
  8. jonr
    Joined: Sep 2008
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    jonr Senior Member

  9. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    This is the discharge vs life cycles you can expect from your batteries
     

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  10. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    One more thing - you will need a larger than 15kW generator to charge the 15KW back into the batteries. Energy is not exchanged on a 1 : 1 basis, the diesel generator motor has losses, the generator has losses, and to top it all you need more than one hour to charge the 1 hour's consumtion back.
     
  11. tugboat

    tugboat Previous Member

    Fanie- thank you for your input and going to the trouble to respond...

    ill take that info under advisement.

    i appreciate everyones input...

    im grateful for this forum to discuss things
     
  12. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    You're welcome Tugboat. You have to realise if there was a gain somewhere in using electric motors, the swing towards it would be considerable and we all would know about it. Electric motors are more versatile, easier to control, cleaner simpler and probably more reliable. It's just the frigging electricity supply that is a problem.

    If there was just a little 5% saving somewhere, it would be considerable, instead it's a loss.
     
  13. CDK
    Joined: Aug 2007
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    CDK retired engineer

    We are generally in agreement, but this may be a special case.
    I would not advise anyone to throw his diesel out and go electric but as I understood it, Tugboat already has the motor or can get it for free, maybe he also doesn't have to reach in his pockets as deep as you and me to obtain the battery bank to power it.

    I visited a guy who has a house in the bush. He had a room full of 100 Ah nickel-cadmium batteries, all together more than 50 Kw and had paid only the transport from a German military airfield to his house. The air force uses the batteries as emergency supply for nav equipment and radios: they are kept fully charged for 4 years without ever drawing current from them and then replaces them because it says so in their regulations.

    Your estimate of the required capacity is based on full load (and so was mine), but actual use will be at partial load most of the time.

    I made an excursion to a nature park with lakes and waterfalls, where passengers are transported with electric steel boats, each carrying up to 60 persons.

    The boats operate the whole day and can only be charged while loading and unloading passengers. The trip takes 20 minutes, they also spend 20 minutes at the jetty, so they can keep on going all day long, up to 10 hours in summer. Despite the 60 passengers the boats accelerate impressively for half a minute, then continue at reduced power and 6 knots, almost silently.
     
  14. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Hi CDK,

    I would still be hessitant to going that way. While it may be fine for now, if the same resources are not available in a year or two when the batteries are beginning to expire, it is going to be a huge expense in maintaining them.

    If worst comes to worst and the motor gives out, then what ? A once off should only be applied to an application that is not required.

    What I will be in favour of, if there are anythinkg like it aboard is to run accessories from the batteries.

    Nice motor, I'm sure it looks impressive and it probably is a fine one, but think with a bit into the future in mind as well.
     

  15. tugboat

    tugboat Previous Member

    CDK- i was rereading my thread which is a couple months old- and I reread the posts here and I think i understand it better now- like a fool- i forgot to mention to everyone that this is for a diesel electric application.
    I just need to charge my battery bank and use the diesel 50% of the time and charge the rest. In fact i can get some batteries for free but I can buy used ones for about 20-25 u.s. dollars each --I would hook up "sets" of batteries and charge them with a series of alternators that would run off the diesel. if i used say 4 or 5 truck alternators at 80 amp charging- couldnt this work?... if i ran the diesel engine just to charge my batts it shouldn't use a lot of fuel. because its not doing a lot of work with 4 or 5 alts hooked up to a shaft. this could charge three banks of the required amp/hrs.
    so if i use the electric engine even a 1/4 the time..i have gained range for my vessel. but its not about range its that i like D.E. systems.

    if your still around let me know your thoughts on this?
     
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