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Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm

Discussion in 'Electronic Design' started by TSL, Jul 19, 2006.

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  1. TSL

    TSL Guest

    Final stage of rebuilding 1940's 10" Craftsman table saw (think
    tank/bulletproof) with belt drive. Been doing some electrical research
    while setting up my woodshop. Using Allen Bradley switches with
    key-lock on/off and 2 e-stop buttons for each of the larger power items
    (one at the switch panel and one on or directly next to the repsective
    machine), along with swap out of all larger 120V tools to special plugs
    so switch panel can't be endrun. Have 13yo son and don't want
    curiosity getting the better of him and his friends in my absence.


    1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
    3450rpm drive motor to give the motor longer life - and if so should an
    electric brake be installed also? What are the theories and pros/cons?

    2) what is the difference in design between a transformer rated switch
    @ 120V 50/60htz versus a "full voltage" switch with identical rating -
    are the contacts supposed to be different? I ask because I noticed in
    my quest for the AB switches (bought used to save money) the contact
    blocks for the switches appear identical in both design and model #
    regardless if they are rated/listed for transformer power versus full
    voltage (which I'm assuming is raw power from my house).

    3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
    mean in motor circuit and wiring diagrams? I'm assuming that "common"
    is the nuetral. And when the nuetral and ground from my box (WA state)
    are joined, how, if at all, are they to be distinguished at the motor?

    Nuff for now. TYIA!
  2. I would suggest you get a qualified electrician in to wire up these items,
    it is evident you don't have a clue.
  3. John Perry

    John Perry Guest

    Heck, just tell him straight out that he can't use that motor. It's
    unlikely in the extreme that his home provides the 3-phase power he
    needs to drive that motor. That's what his electrician is going to tell

    John Perry
  4. On Tue, 18 Jul 2006 23:10:47 -0400,
    Depends on where he lives. In Europe, 3-phase 400V lines go into every

  5. The only possibility for you, will be a 3 phase inverter unit. The motor
    you have, is industrial, and built to run on 3 phase. it sounds as if it
    can be wired for either star, or delta configurations (hence both ends of
    each winding are available). A normal house supply, will only be single
    phase, so three choices exist. First to pay to have 3phase electricity
    supplied to your house (expensive), or buy an inverter unit, which
    generates a 'synthetic' 3phase from your single phase supply. The latter
    in general, is significantly cheaper than getting 3phase power, and has
    the added advantage that most units will include options for soft start,
    and variable speed. The third option is to substitute a single phase
    Look at:

    The SV022iC5-1F, would probably be the unit for your motor.
    However _seriously_, if you have to ask the question, you do not have the
    experience, to wire such a unit safely, and if you value your own, and
    your families lives, you should consider getting a professional to set
    this up for you.

    Best Wishes
  6. Glen Walpert

    Glen Walpert Guest

    A motor starter (controller) should be used with any motor you want to
    protect from overload, and the overload trip elements in it must be
    sized to the protected motor. Look for a table of trip element number
    vs full load amps (FLA) and buy the right trip elements new.
    Perhaps different voltage rating between coil and contacts? Try the
    mfgr's web site?
    L1, L2 and L3 refer to line in of three phase power, T1 etc are the
    motor terminal connections for a 3 phase motor. If these are on the
    wiring diagram for your controller and you have a single phase motor,
    no problem, run your two hots in L1 and L3 and out T1 and T3, after
    verifying that L1 - T1 and L3 - T3 are the circuits which contain the
    overload elements. If these designations are on your motor then it is
    a three phase motor and you need a phase converter. There is a good
    rotary phase converter design posted to the rec.crafts.metalworking
    newsgroup "dropbox", someone on that NG could tell you where it is.

    The difference between neutral and ground, which are joined only in
    your panel, is that the neutral normally carries load current and the
    ground *only* carries fault current in the event of a short circuit to
    ground. Unless you need 120 V for the controller coil you should not
    even need to run a neutral to a 240 V motor circuit, but the ground
    (AKA safety ground) is always mandatory and must be connected solidly
    to all metal enclosures of energised equipment.

    While I have no problem with DIY electrical work, I very strongly
    recommend you have your work inspected by a licensed electrical
    underwriter (inspector), and that you line up the inspector and
    discuss the job with him before you start.

  7. The motor data indicates that it was made for the US market, and he
    is posting from a US based ISP.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  8. TSL

    TSL Guest

    OK Gentlemen, first it would appear that this request for assitance is
    misplaced in this advanced a forum. Second, it IS NOT a 3 phase motor.
    It is a 1 phase motor - and I am very clear about the difference. I
    asked about the L3 as an abstract type question not specifically tied
    to my situation.

    And at the risk of displaying obvious umbrage at some of the remarks, I
    most definitely do have a clue about AC - at least the 120/240V variety
    common to my home. I simply need some additional information to fill
    out the gaps.

    Should it help establish my level of understanding, I have completely
    rewired and redesigned the circuits in my 3 bay garage to make sense
    for the machines and power needs I employ, including a 'pony box" with
    a 60 amp 240V draw off the main box so I don't have to run wire so far.
    I've also succesfully installed a ten circuit gas generator interface
    for when the power goes out (which happens 4 to 5 times a year from
    nasty windstorms).

    I won't pretend I completely understand 3 phase - but I can tell you
    that I don't have it in my home and I am not interested in using a 3
    phase motor, dirt cheap though they may be, as I have a perfectly good
    2HP motor.

    So perhaps we could start over.

  9. Tim Wescott

    Tim Wescott Guest

    I second that. I'm an electronics engineer with a master's degree, 15
    years of experience, 5 years of electrical installation experience
    before that, etc., etc. -- and if I did work of that magnitude in my
    home I'd happily pay to have a second pair of eyes take a look at it
    before I fired it up.

    Most insurance companies will deny coverage (or at least try) if
    home-done, uninspected electrical work catches fire. Many will try to
    deny coverage if an arsonist starts a fire on the outside wall of a
    building housing such work. Getting the thing inspected in small potatoes.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
  10. TSL

    TSL Guest

    OK, now were getting somewhere. Thank you Mr Walpert.

    I am clear about the difference between the ground and nuetral in
    general terms. What I am unclear about is why a 240V motor (which is
    also on my compressor) does not need the nuetral? This is one of the
    gaps in my understanding. It bugged me when I hooked up my compressor
    but i just let it go. With what I am doing now, I'd really like to
    understand why 240V seems to change the whole playing field and drops
    the nuetral.

    My Dayton 1 PHASE 2HP 115/230V, 21amp/11.5amp, 3450rpm motor on a nema
    H56 frame is sealed so as to not allow in wood dust and chips and
    debris and is specific for my application. I am clear that I have the
    option of either wiring it as 115 or 230, but the 10.5 amps running
    through 2 hot lines is an easier and smarter move for my situation than
    21 amps through one hot wire. I have a 240V dual 15amp breaker in my
    pony box that awaits my wiring. I will take power from it down to the
    control panel and run it through an AB 2 position maintained key switch
    with two contact blocks on it (a 120 line going to each contact block)
    and then through a 2 position estop button on the panel, also with two
    contact blocks. Then it will run to a stud mouted outlet with a
    twist/lock receptical. A ten gauge industrial sheathed cord with the
    male plug then runs to another identical estop positioned on the saw
    itself, then to a 240V foot switch, and then to the motor. But as I
    started getting deeper into the AB world, I bumped into these motor
    starters and as far as I can tell, they are used on 1 phase motors in
    some instances. As best I can tell, they help the motor ease into full
    rpm and give it "cleaner" power and better circuit protection - which
    is supposed to increase motor life. Thus my question about using a
    motor starter setup between the control panel and the wall outlet. But
    it may just be overkill and hubris - I don't know. I need help
    understanding the pros/cons.

    While I thank you for your concern, I work at an establishment with a
    full time maintanence crew; one of which is a certified elctrician. I
    am very clear about the code in my area and have followed it to the
    letter; including distances from outer stud to romex feed holes, proper
    gauge romex and proper amperage outlets etc.. My 3 bay garage is almost
    totally bare rafters and studs and thus it is very simple to run romex
    along the top of the rafters and staple them in along other existing
    wires. In the cases when I dropped a wire to one of the 2 small
    finished walls (code mandated with fireproof drywall where garage meets
    house) I start conduit in the rafters and route it down onto the
    drywall. I am a systems geek by profession and extremely meticulous
    about safety in all my endeavors; right down to safety glasses and ear
    protection when I just mow the lawn.

    As to the transformer versus full voltage, I entertained that the
    voltage may be different. But when they attatch an 800T-XA contact
    block that will handle up to 600V (though only at 15 amps) and the same
    contact blocks are used on both, and the operators themselves show no
    design difference whatsoever, I began to wonder whether it was just a
    case of categorization to satisfy NEMA or that other standard that
    escapes me at the moment. It may only be something employed with the
    illuminated switches. But the illumination contact blocks for the 120V
    full voltage and transformer voltage appear identical in both style and
    design #.

    Again, thank you for your time.
  11. TSL

    TSL Guest

    OK, OK, I get it. I'll have it inspected. You had me @ the insurance
    thing . . .

  12. Guest

    Robert Latest wrote
    No they bloody don't! European electricity supply undertakings are very
    reluctant indeed to supply 3 phase power to anywhere other than
    industrial and commercial users, where there is no alternative. In fact
    you may as well say that domestic customers are limited to 230v single

    However 415v three phase lines are buried in the street, and houses are
    supplied from phase + neutral.
  13. ehsjr

    ehsjr Guest

    Perhaps a DC example would help.
    View in fixed font

    + | | |
    ---------- ------- |
    |Battery 6V| |Bulb 6V| |
    ---------- ------- |
    | | --------
    +----nnnn----+ |Bulb 12V|
    + | | --------
    ---------- ------- |
    |Battery 6V| |Bulb 6V| |
    ---------- ------- |
    | | |

    For the purpose of the analogy, call the wire labeled nnnn
    "Neutral". It is easy to see why it is needed - it makes
    both 6V bulbs "happy". They get 6 volts each, and will
    continue to work if the other 6V bulb burns out. They will
    both glow at the proper level, even if the top one draws
    7 amps and the bottom one draws 300 mA.

    Eliminate the "neutral" wire and those 6 volt bulbs may have
    a problem. For example, if there was no neutral and the top
    one tried to draw 7 amps, it would have to draw it through
    the bottom bulb. If that bulb was rated only for 300 mA, it
    would burn out.

    The 12 volt bulb doesn't need the neutral. It gets the proper
    voltage from the two wires marked "hot" with no need for an
    additional current path.

    In your resisdence, the incoming 240 volts comes off a center
    tapped transformer, anologous to the two batteries above.
    Your 120 volt appliances are analogous to the 6V bulbs. Your
    240 volt motor is analagous to the 12 volt bulb.

  14. TSL

    TSL Guest

    OK great, we have established 3 phase power is not a European standard.
    But this is moot to my issues.

    I've still got 2 of my questions unanswered. Should I ask them in a
    different forum than design? It's not that I don't appreciate the
    involvment and time expended thus far, it's just that I need some
    answers. The electrician at my work is Italian born and speaks English
    with a classic, heavy Italian accent. He and I get along great. But
    when I ask these particular questions, I don't seem to be communicating
    well because he looks at me with some confusion - plus he talks fast
    when he gets going. I'm not going to have an inspector come out in the
    very sprawled and busy county I live in just so I can get some
    questions answered. I would rather wait until I get it all done and
    respect his time.

    So I still need help. If this is the wrong venue, please point me to
    the correct one
  15. TSL

    TSL Guest

    FANTASTIC - thanx Ed. One down. Two more to go - care to take a whack
    at my motor starter & brake issue, Ed?

  16. ehsjr

    ehsjr Guest

    Well, I don't have much to say about it. As I see it,
    you've done the "good stuff" - brought a 60 amp line
    to the location with a 20 amp circuit for the saw.
    I think the additional electrical work (motor starter
    & brake) beyond that is pointless. (I suppose that if
    it's a new motor, the manufacturer would recommend
    starting and braking circuitry as needed.)

  17. Rich Grise

    Rich Grise Guest

    In a nutshell, the neutral is the center-tap of the 240V transformer
    that feeds your house, so you get 120 to neutral on the black, and
    120 to neutral on the red, and 240 from black to red. When your
    device is using the whole 240, the neutral is irrelevant - when you
    use a 120V item, all its return current flows through the neutral,
    which is why people like to balance the loads on the two legs (which
    some people erroneously call "phases" - there's only the one phase,
    but the 240 is center-tapped) just because it's nice to minimize
    the neutral current - it evens out the load on the halves of the
    secondary of the pole pig.

    Maybe visualize a loop or three... ;-)

    Hope This Helps!
  18. Rich Grise

    Rich Grise Guest

    I don't know the exact rules in the US, but my cousin's farm has had
    3-phase since I can remember, and I somehow think that if you paid for
    all of the wiring, transformers, work, etc, the power company would
    be happy to string any kind of power you want to your house. :)

    If I'm wrong and there's some kind of rule against it, I'd be happy
    to be enlightened, so to speak. ;-)

  19. Rich Grise

    Rich Grise Guest

    On Wed, 19 Jul 2006 09:08:44 -0700, TSL top-posted:
    [some snit]
    I don't understand the problem - if you already know that stuff, what are
    the questions for?

    But just because I'm such a smartass, here ya go:

    Yes, and I wouldn't try to use an electric brake on a motor that old
    without talking to the guy who's selling the electric brake, and maybe
    having the motor checked out by a motor shop.

    You'll have to ask the guy who's selling you the switch.

    This is the generic "line - terminal" question which has been answered

    So, what's the problem?

  20. Rich Grise

    Rich Grise Guest

    He doesn't have a 3-phase motor. He's got a 240V, single-phase motor.
    That question was just a red herring.

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