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Electric Motors/ajax motor wiring



       Kind of off beat question here. Ajax model KXD 145TBFR7029AB W -  frame 146T - type BFR

code K  - 115/ 230 volt -1 phase-60 cycle-2hp. -11a.@115v

  capacitor start, capacitor run-(I presume anyhow)- centrifical switch- 2 caps on the start winding, 1 cap for the run winding-( as I am seeing it )Start caps are wired in series- No wiring diagram, no numbers on the wires.

   From what I know of it the motor came off a high pressure car wash pump. Every so often the motor will fail to start -before it comes up to speed it will growl like it has loose iron in it and trip the breaker.  When it starts it seems to run fine, amperage is good, runs smooth, power is good. It does this maybe every 30 starts or so. What seems really odd is that when the motor is shut off (no load connected) it makes you think there is regenerative braking taking place after the cs closes. I work on this kind of stuff all the time so not a novice. It strikes me there is something I am failing to grasp here. Any ideas before I tear it down? I have looked for a wiring diagram with no success. Thanks, Doug

Doug  what part of the world are you in?  Likely looking for experienced motor guy here in the KC mo area,  pay is normally above even union scale,    ??

Not of the path at all   unless you came in on my electical home problems log  I have a motor problems login  too       

Here is the first thing to look for,   and great description of the problem by the way!

Look at the caps.  Are there discharge resistors on everyone,?  The clue is in the dynamic braking sound,    the caps may be discharging back into the windings and that is EXACTLY what you are hearing,       

Next it might be just a bad cap,  or all,   that would explain the lack of out of phase as the start winding attempts to create that out of phase relationship.

It is likely not an incorrect external connection,  but while it is connected is the easiest time to ohm the windings out and number them     

IF the switch contacts are charred or the spring metal is fatigued either might cause this intermittent no start  rumble down sound,     but it as you know the most difficult repair of the three I mentioned to check

Finally if it has a centrifugal spool, and the bore of the spool is worn it will allow it to cock and stick at times,   or the springs on the centrifugal are worn out,      or again as you know a little of all    

Either the caps are not discharging, correctly,  or the cap is bad and the discharge is over heavy,  or the resistor is open or high resistance connected to the cap terminals,    

The high current that trips the breaker is any of the above, but the root is speed without the start winding not completely out of the circuit,      I assume the running current it within tolerance?   The applied voltage in tolerance?

If it came off a car wash it is OEM to the carwash and you will only MAYBE find the connection diagram from the OEM     as they want to capture the replacement parts market  they will do something in ordering the motors to make them non NEMA    

But it is wired  and dual voltage so you should be able to identify the run windings,  and the starts because they are bundled right now,    find a run,  short the caps, ohm it out, it can be arbitrary   call the first run 1  its end  2   then the second half   will be in the other bundle  so mark the start of the second half of the run 3    then maybe the start leads are smaller     maybe       mark one 5   and the other 8      now it depends if they stuck in common leads, and over current leads in series with either or both windings,    you know how to find the EASA handbook on line    use      electric motor single phase connections  as keywords and you will find either the pages showing multiple leaded single phase motors or the whole book in pdf format,        

But the best thing as electric is going up and up and up  is to go ahead and give it a good cleaning,   check you switches for the things I have explained,   pony up for new caps with resistors,   [often an option, with or without discharge resistor] or solder one on yourself,   there is a formula based on mfd  to tell you the value of the resistor to use,

And very last it is rare to find caps in series,   as they add in parallel  so why put two in series   why not use a lower value single cap  ?   I would be suspicious of that series cap connection.

Make sure your housings are not oversized,   look for drag marks,  look at the machine fits on the end housings for burrs    do not use a file or grinder,   use a stone and the high dings will shine up,    then use a stiffer stone to smooth,   a cocked end housing will cause all kinds of issues,  or a loose housing,    bore it and put a bushing in    no machinist in a bottle   and make sure only one end is captured,  for thermal growth,   I find motors locked on both ends all the time,   if they are there is no room for growth but in the wrong places,  

Make sure your endplay is not tight nor loose  there should be some but measurable by a dial indicator,  if you can see it it is too much,     mark any thrust washer or flat washers and tie them in order, on the same ends,       it could also be as an after thought  a worn out thrust washer and it is pushing or not pushing at times,   moving your distance from centrifugal to your stationary   which is the same as a worn or loose tension on either  

Tip  use a drill   to mark your assembly   one 1/32 drill mark or around there, on the shaft end   two on ode     look for any wires that may be drifting and not secured rubbing into another     clean with soap and water bake at below boiling  as over that bubbles can form and burst insulation     but get it clean as possible    the hottest spot on any motor is deep down and all motors cool to the outside frame,   so any build up is holding heat and not  being transferred out,     somewhere you will find the issue,    take photos as needed during tear down,  you never know,       

If you find nothing       and replace the caps   and it still does it,  let me know and we will dig further,    got an internal growler,  ???  look for any dots of melted mylar at the slot ends,  shorts will hide and the windings can be easily shorted above ground,  dont be fooled     megger it,    

My guess is either a bad cap or missing resistor,   likely that someone before you has replaced caps and said     oh this new one dont have that little wire across there   and didnt bother to move it from bad cap to new,       and that makes sense because those series caps is a warning sign        that someone was jacking with this before you     there is a nema cap start cap run diagram in the easa handbook,     but if you use the keywords I gave you will find a hundred diagrams but they will be nema keep that in mind      but let me know how it goes         and you got my direct email if you want to use it     easier than this but about,com    spends a fortune helping people,     a thank you to them would be a nice thing to do,   their whole idea is to pay forward,     they have more intense background checks than paid sites,  

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Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site


30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.

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