Click for Dockmate Click for Cheoy Lee Click for United Click for Abeking Click for Westport

Roto Phase motor

Discussion in 'Technical Discussion' started by libertyac, Jan 26, 2009.

You need to be registered and signed in to view this content.
  1. libertyac

    libertyac New Member

    Joined:
    Jan 5, 2009
    Messages:
    28
    Location:
    Freeport Bahamas
    Can anyone suggest a test to see if the 230V single phase motor is OK?
    When my bow thruster didn't work, I dug around and found that the Roto phase was disconnected with the terminals T1-T3 going nowhere. The 3-phase motor works when connected to 3 phase power, but it is the starter or step-up motor which is out of the circuit.
    Is there some form of resistance test by which I can avoid putting power to the motor and risk damage to the circuit?
    Since this is an inherited problem I have no History to go on.
  2. Marmot

    Marmot Senior Member

    Joined:
    May 20, 2007
    Messages:
    3,315
    Location:
    9114 S. Central Ave
    This is a bit murky. The way I read your post is:

    You have a 230V single phase motor somewhere and you are not sure if it works properly.

    You used to have a 3 phase bow thruster

    That unit may have been powered by a rotory phase converter

    The phase converter is disconnected

    A 3 phase motor someplace works when powered up

    There may or may not be a motor starter for the 3 phase motor

    There may or may not be a "step up motor" in some circuit

    You don't want to apply power to the 230V single phase motor but want to know if it works.

    Is that accurate? What is a "step up motor?" Is that what you call a rotary phase converter? If T1 and T3 are disconnected from the converter, how does it run the 3ph motor you mentioned? Do you have a separate 3ph supply available that runs the 3ph motor?


    Supply the nameplate data off the motor you want to test and I or someone else might be able to provide you with a starting point pretty quickly.

    Electrical problems are sometimes difficult to troubleshoot online but it can be done if very clear descriptions of what you have and what it is supposed to do vs what it appears to do or not will increase your odds of getting some help.

    Otherwise, hiring an electrician to attend the vessel may be your best solution.
  3. libertyac

    libertyac New Member

    Joined:
    Jan 5, 2009
    Messages:
    28
    Location:
    Freeport Bahamas
    Last time I used an electrician on this Island I got stung $1800 for trouble shooting the same problem and they didn't find that the phase converter was disconnected. Their theory was that it was the inverter, which cost me a further $850.
    It was only when Ithe time to investigate that I discovered the taped up wires.
    My simple question is , how can I test the phase converter without applying power? Can it be statically tested with a meter?
    I have the roto phase diagram so once I know whether the motor is good, I'm sure I can follow the schematic
  4. Marmot

    Marmot Senior Member

    Joined:
    May 20, 2007
    Messages:
    3,315
    Location:
    9114 S. Central Ave
    It sounds like you have a 3phase motor that was wired as a phase converter to feed another 3 phase motor that drove the bow thruster. Is that correct?

    If that is the case, take the motor being used as a phase converter to a workbench with 3 phase power and see if it works, you can't hurt anything as long as the supply is fused to match the starting current of the motor. If there is a motor shop nearby they can test it for you very quickly and may do it for free or very cheaply hoping they will get to sell you a replacement. It is really quick and easy to bench test a motor.

    Since you have the wiring diagram, if the motor works, rewire the system according to your diagram and replace the single phase bow thruster motor with a matching 3 phase motor and you are in business.

    Have a look at this site:

    http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

    These guys have been helping home machinists who lack 3 phase power to get their surplus machines running for years.

    Google "build rotary phase converter" and you will get a pile of links with wiring diagrams and explanations of how they work. That may go a long ways to help you sort out your problem.

    http://www.metalwebnews.com/howto/phase-converter/phase-converter.html

    Good luck, let us know how you do.
  5. TedZ

    TedZ New Member

    Joined:
    Dec 27, 2008
    Messages:
    13
    Location:
    Clayton, NY 1000 Islands
    Does the motor have nine or twelve leads. I can give you ring-out parameters you can check with a meter if i know the number of leads.

    Ted
  6. TedZ

    TedZ New Member

    Joined:
    Dec 27, 2008
    Messages:
    13
    Location:
    Clayton, NY 1000 Islands
    Or 6 or 3 leads but not common. I am going to be away from my computer.

    Look here. http://www.elec-toolbox.com/usefulinfo/mtrconn.htm

    The "2" is missing from the Delta pictorial. If you make the connection at 1, 2 and 3 you can ring the motor out. You need a decent meter as the resistance will be from a fraction of an ohm, say .33 ohms, to a few ohms, say 2.3. If they are not close when measuring equal length leads or they are open or they go to the frame (ground) anywhere, then the motor is bad. If they ring out ok, the motor could still be bad when under normal voltage or a load but they usually smell...course you can't smell much on a thruster unless on the hard.

    Good luck.

    Ted
  7. libertyac

    libertyac New Member

    Joined:
    Jan 5, 2009
    Messages:
    28
    Location:
    Freeport Bahamas
    Roto Phase

    Thanks Marmot and TedZ. When I measured ohms across all 3 visible wires, I got aneven 1.8.I checked out the Arco Electric site and they have a pretty good diagram which may help and I'll check out the suggested sitesn as well. Then we'll power it up.Trouble is, some wise-guy built a cabinet over and around it so access is almost impossible without surgery.
  8. libertyac

    libertyac New Member

    Joined:
    Jan 5, 2009
    Messages:
    28
    Location:
    Freeport Bahamas
    Pics of the "system"

    Attached Files:

  9. Marmot

    Marmot Senior Member

    Joined:
    May 20, 2007
    Messages:
    3,315
    Location:
    9114 S. Central Ave
    Ah, I see the problem now ... that red wire connected to the blue thingy in the top picture is loose.
  10. TedZ

    TedZ New Member

    Joined:
    Dec 27, 2008
    Messages:
    13
    Location:
    Clayton, NY 1000 Islands
    Boy! Are we supposed to comment on this? And is all of this for the thruster?

    A few things bother me but these are just guesses. For one the the three phase contactor with only two wires attached...presumably the power to the single phase side has solid wires where thermal overloads typically are found. I may be wrong, keep that in mind, but if that is the case that is a good way to burn up the single phase motor. It appears there is a reversing contactor in the upper left. Does that have an electrical or mechanical interlock. If electrical, check it out so you are not trying to run the single phase side both ways at the same time. Lastly, there are a lot of contacts to go bad. All of those need to be checked and cleaned.

    Remember, all guesses.

    Hope this is some help!

    Ted
  11. libertyac

    libertyac New Member

    Joined:
    Jan 5, 2009
    Messages:
    28
    Location:
    Freeport Bahamas
    Just thought I'd show what I've inherited. It's scared away a number of wanna-be electricians, but one who works in the cruise ship repair yard has promised to take a look. Surely there's a simpler system!
  12. Marmot

    Marmot Senior Member

    Joined:
    May 20, 2007
    Messages:
    3,315
    Location:
    9114 S. Central Ave
    "Surely there's a simpler system!"

    If all you are trying to do is run the bow thruster, then yes, that is an understatement. Look at the links I provided and just add a reversing relay. This is not rocket science.
  13. TedZ

    TedZ New Member

    Joined:
    Dec 27, 2008
    Messages:
    13
    Location:
    Clayton, NY 1000 Islands
    It is not rocket science but the fact that there apparently is a 3 phase thruster with only single phase power available complicates it a bit.

    Ted
  14. Marmot

    Marmot Senior Member

    Joined:
    May 20, 2007
    Messages:
    3,315
    Location:
    9114 S. Central Ave
    We the readers still don't know if the thruster motor is single phase or three phase. You asked how to test a 1ph motor then started to describe a 3ph system.

    Reading between the lines of your posts, it seems as if the bow thruster is now powered by a single phase motor because of some previous failure in the system. Did the 3ph thruster motor fail and was replaced with a 1ph or did the kluge of a control panel die and the converter is being bypassed altogether to drive a 1ph motor and the convertor motor is out of circuit?

    Judging by the photos, there appears to be a another control feature and some sort of dispaly which may or may not be functional at this time. Like I wrote earlier, it is very difficult to troubleshoot electrical failures via a BBS and more so when most of the relevant information is missing. If you have the circuit diagram available most competent electricians should be able to troubleshoot the system. If you don't then it probably isn't worth throwing more money at it.

    What is not rocket science is the fact that if you want to use a 3ph motor to drive your thruster but only have 1ph onboard you can make 3ph via a rotory converter and use a simple reversing contactor to control the thruster direction. The circuit is simple and cheap. This can be performed with a minimum number of components and you can dump the overly complicated and probably hideously priced collection of stuff some fool got talked into before you bought the mess.
  15. Capt Bill11

    Capt Bill11 Senior Member

    Joined:
    Feb 27, 2006
    Messages:
    1,428
    Location:
    Sarasota/Ft. Lauderdale FL
    My thoughts exactly.

    The display device is I believe a 3 phase inverter and /or a freq. drive. Perhaps used as both a soft start and to get the three phase power.

    It looks/sounds to me like systems have been bypassed and/or replaced as other systems failed. My guess is the inverter replaced the rotary converter or vice versa. Because I don't see why you would need both.

    Of course there only seems to be two wires hooked to the motor so perhaps it all failed at some point and they were running the motor at reduced speed in single phase.

    I vote rip it out and start over and KISS it. :D
  16. wdrzal

    wdrzal Senior Member

    Joined:
    Feb 6, 2006
    Messages:
    363
    Location:
    Baltimore
    There are 2 ways I know of to start and run a rotary phase generator.

    1: use a pony motor,like 1/3 or 1/2 hp ,energize it, and by belt or direct drive bring the larger 3 phase motor up to speed before energizing it. Failure to due so will cause the 3 phase motor not turn ,overheat and then fail.

    I would bet this is what the smaller motor is for & all the complex wiring. To first energize the pony motor,when phase generator is up to speed ,energize it and stop power to pony motor. Early phase generators used this method.


    2: By the use of a capacitor bank create enough phase offset to get the rotary 3 phase generator started without a pony motor.


    One another note: A rotary phase motor will generate L1 & L2 @ supplied single phase voltage but L3 will be a lower voltage. 3 phase power ,L3 is a higher voltage (leg) than L1 & L2. The low leg from a rotary phase generator can also be corrected by the use of correctly sized capacitors.

    I don't see any capacitors in the pictures, so method 1 is how I would say your system works and they just accepted the low voltage on L3.

Share This Page