motor starter problems

[David Kumm]

I'm rehabbing - a loose term- an older SCMI sliding table saw. 6.6 kw-9 hp motor. When I push the start button the starter clicks, flashes, and usually two, the same two, overload breakers trip. Once the blade spins enough the starter will work and start the saw just fine. Problem seems to be turning the blade from a dead stop or close to it. I replaced the starter a Klockner Moeller dil 1M with same result. Any opinions as to whether the breakers might be failing and overloading prematurely or is there another problem. I replaced the arbor bearings but not the motor bearings. Everything spins easily, belts are adjusted. There isn't a soft start feature as in newer machines of that motor size but there is a separate on-off that cuts power to the switches. I can't see where that could be the problem but am open to any suggestions before I replace breakers. Dave

[Mike Heidrick]

9hp is bigun!

Can you take pics and get us as much info as you can. Draw a diagram maybe? You threw me off when you said two overloads.

Also how long a cord is this on and what size? Three phase I assume correct - how is that setup and powered?

Has it ever worked? Is this a recent/new problem?

Another thought, you might want to join the Felder Owners Yahoo Group and post there too. Sharp boys here and there. The have a lot of sliding table saw experience there as well. OWWM as well.

[David Kumm]

The cord is 8 ga hooked to a PP. There are three overloads, one never trips, sometimes two but mostly two and three together. The PP doesn't trip it's breaker so I'm assuming it is OK although it is only wired to a 50 amp breaker in my storage building. Supposedly new problem but the shop that had the saw might not own up to any problems which seemed to get worse as I was testing it. I posted on MM and Fog will follow. Dave

[Van Huskey]

I can't help but to clarify I assume you are talking about an overload on each leg of the three phase correct?

[David Kumm]

Yes, Klockner Moeller FAZ multivoltage overload breakers on each phase. Listed at 50 amp at 230 volt. From what I can figure- and I'm guessing here- the SCMI used multvoltage electronics and a transformer to get either 220 or 440 to 110 for the coil. Other than swapping leads on the transformer, no other modifications were necessary to change voltage. The breakers seem like they should not trip before the breaker on the PP as it is hooked to a 50 amp single phase breaker. I'm sure when I find the problem it will be totally unrelated to any of my logic. That seems to be my style. Dave

[Van Huskey]

I am assuming they either aren't adjustable or adjusted for the correct current draw, as you know 3ph motor control is NOT my forte' so I am just swinging in the wind.

[Rod Sheridan]

First check is to determine whether it's a 3 phase motor (sounds like it may be). Of course if it's 3 phase don't try to run it on single phase power.

Secondly, more than changing the transformer tap is required to change voltages, the motor windings will have to be re-connected for the correct motor. Please check that as well.


If it's a 220/440 volt motor, it most likely is 3 phase..................Regards, Rod.

[David Kumm]

Yes, it's 3 phase- mostly what I run. Motor was wired 230 when I got it and runs fine once started. Both starters i've tried seem to click in and out and short rather than fully engage- but only when the blade is stopped. When it is winding down from a previous stop it will restart with no problem. Dave

[Van Huskey]

Never mind Dave posted while I was posting.

But I will ask a question to satisfy my curiosity, what is the FLA of the motor?

[David Kumm]

About 22 on the main motor. I'm also wondering if the Phase Perfect might have an internal shutdown momentarily but seems unlikely and it should just trip it's own breaker if called to supply more amps than it can. The 50 amp breaker on it is marginal for this motor but it never trips. Dave

[Van Huskey]

Do you have a muti-meter fast enough to measure the inrush?

I'll shut up now and let the big boys think when they get here!

[Kirk Poore]

Since you're having the same issue with two different starters, I think it's unlikely that the starters are the problem. 3ph motors are dirt simple, so that's unlikely to be it. Your other common elements, then, are the phase converter and the wiring. PP is a Phase Perfect phase converter? Have you measured the voltages for each phase? Also measure the amps, during startup (if possible) and after you manage to get it running. On the wiring, have you checked all of your connections?

I'd say you've got a bad connection or one of your phases is out of balance. But I'm not super experienced in this area, I've just dealt with similar issues on my machines.

Kirk

[joe milana]

How about trying to run another machine of equal or more HP off the PP to eliminate that as the problem.

[Jeff Duncan]

1st off did you see the saw running when you bought it?

I can't offer any technical advice but will give you one additional thing to look for. I had a different though similar problem on my Bandsaw (3ph), sometimes it would start, sometimes it wouldn't....pretty annoying actually. I looked everything over and was sure it was a faulty overload located behind the switch. I tinkered with it and tried increasing the amp setting but nothing worked. Then just before ordering a replacement part I decided to go through the whole machine again.....and found the real problem. One of the wires on the terminal block connecting the motor to the power supply had gotten just a little bit loose in the move. Enough so that it apparently wasn't making a full connection every time. I tightened the connections and it's run fine ever since. So I'd take a little time and just make sure all your connections are good and tight before ordering any parts;)

I might also try pulling the belt and seeing if the motor starts with no load....though not sure what that says.....just something I might try!

good luck,
JeffD

[Mike Heidrick]

What size phase perfect is it?


They bring a whole unique element to your mix.

Where are you Rick?

[Rick Fisher]

Hey David..

My PP has an Automatic Shutdown .. I call it " tripping " ..

No idea why it happens but its only happened to me starting a 12hp motor .. The PP just goes silent.

David, I would bet that motor uses star for starting and switches to Delta to run ? No idea, but I wonder if the problem lies somewhere in that area ?

I cant see the breaker size being the problem, if it was, it would just trip .. The momentary overload on the PP would handle it .

[David Kumm]

Rick, when your PP trips does it start back up on it's own? The one I'm using now is on a 50 amp breaker as that is all that available in the storage building but that breaker doesn't trip, only the motor overloads do. I would agree that it should have star delta starting. I will mess with the overloads, bypass the transformer if that doesn't work since I'm running 230 the transformer doesn't serve much purpose. If that doesn't work I'll have to take off the motor- 150 lbs- and have the motor guy check it and change bearings at the same time. Removing the motor is my least favorite option. Dave

[Rick Fisher]

David..

Its tripped about 3 times in 5 years .. maybe 4 ... I run mine off a 100 amp breaker, I snap the breaker and its on.. When it trips, I have to turn the breaker off an on..

Its unlikely that the Power supply is the problem . Phase perfect units will supply 500% of the maximum the set-up will normally supply for 4 seconds.. With a 50 amp breaker, your PP should be supplying about 27-28 FLA .. So it can supply your motor with say 130 amps of starting current.. A 9hp 230V motor like that should draw 100 amps max start-up .. unless its an odd-ball, or sick ..

So at 50 amps in, its close, but should work ..

A PP will reset itself from a thermal overload.. From an over-current overload, it wont.. I am willing to bet my few trips where just that..

[Rick Fisher]

David .. Just completed my thought from earlier today .. lol

The starters overload is rated for 50 amps x 220V ?

The PP will likely supply about 130 amps for 4 seconds..

Could it be that if the motor was wired wrong, it would be trying to start, and run in Delta ? .. rather than starting in Wye and switching to Delta.. ??

If that was the case, it would draw much more than the overloads where rated for, and the PP would easily supply it for 4 seconds.. 4 seconds is likely more than long enough to trip ?

I don't really know if that's possible .. I dunno ..

****

A star / Delta motor starter has 3 magnetic switches.

As an example, My single phase dust collector has 2 motor starters.. When you press the start button, the first contactor engages both capacitors and the start windings. Both caps are 80uf ..

When the motor reaches speed, the second contactor automatically engages and the first contactor drops out, removing one of the two capacitors and the start winding's from the circuit .. ( The DC is single phase but not really simple ) ..

So on star delta, your motor will have 6 leads coming from the winding's .. Upon starting, 3 of the leads will be " hot " .. after it reaches speed, the other 3 become " hot " and the first 3 drop out .. The contactors accomplish this ..

You should have 3 contactors.. one will probably have a timer installed on it .. The first contactor starts the process.. the second is the star contactor .. it controls 3 of the wires to the motor .. The time will let it stay in the circuit for a specific amount of time .. The last contactor is the Delta.. The Delta is probably the one that never trips..

So in your case, if the incoming and star contactor are tripping it could be a faulty transformer .. If the incoming and Delta are tripping.. well.. I dunno..

[David Kumm]

All, I worked some more on the starter. Bypassed the breakers on the machine and wired into a 30 amp fused disconnect instead. Allowed me to start the machine but the coil doesn't pull the magnets together quite right so it clicks in and out a couple of times and then engages. If I push the magnet in with a stick the motor starts just fine. Voltages are good, PP is fine and the 30 amp fuses work. Wondering if the motor just starts a little harder than the starter allows. K-M DIL 1M so I'm at the top end of the 24 amp motor size. I know the NEMA size would be 2 but don't know how the euro starters compare. Dave

[Leo Graywacz]

Sounds like a weak coil now.

[Rick Fisher]

You think the overload is shot ?

I would still test the Transformer .. The motor will start with a faulty transformer unless the overload stops it .. If that is happening .. the motor will suffer greatly ..

[David Kumm]

The starter is new and acts like the old one. I don't know much about transformers. Square D 9070 ser B E-03 230 to 115. There is an X1 and X2 on the 115 side. X1 is hot and goes to the starter coils. I don't know what X2 does. If I test it to ground I get nothing. The second starter for the scorer works just fine although it is much smaller. Dave

[Rick Fisher]

The big transformer reduces the voltage during starting and during the " star " portion of the process..

The overload would stop the entire process if the transformer failed to do that ..

So the voltage drops, allowing the star portion of the process to use significantly less amperage during start up .. When the motor is running during this time, it has no power ..

Then the star drops out, along with the transformer.. and the Delta kicks in at 230V .. And your 9hp motor is alive and kicking..

[David Kumm]

Rick, does the fact I can start the machine manually by pushing in the starter indicate a transformer problem? When the blade is spinning somewhat the starter works fine as well. At dead stop the coil doesn't quite engage-- click- click- start. Sorry for lack of technical terms here. Anything else to check. All leads tight and wires making contact, put new contacts on start button. Dave

[Rick Fisher]

David .. I am no expert.. My concern is giving you bad info .. That motor is likely worth $2500 to replace ?

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1020350.jpg

All of that with the exception of the small black current transformer is in place to start the motor .. Contactors, an overload and a transformer .. The little black transformer is just to read the ammeter .. That set up controls a 12hp motor on my sander.. not really that different than a 9hp motor ..

The new system for running these larger and medium sized 3 phase motors is motor drives.. We use them to create 3 phase power but their real purpose is to control the amperage and voltage during start-up of one of these motors.. Soft start is a big deal when the motor will draw hundreds of amps if started improperly..

I think I would phone SCM in Atlanta and ask them .. at the age of the saw, they will have seen it before.. They are quite helpful.. They may scoff at the transformer but just getting the motor running does not always mean its fixed..

[David Kumm]

Thanks, Rick, I plan to call. Just needed to get enough info. Your pic is very similar to my set up. Two master on-off modules, Moeller starter is the same. What is the lower right module? I have a second starter but otherwise very much the same. Dave

[Casey Carr]

I had a similar problem with my jointer. May be the same, may not be. Starter would just click when I pushed the button, but it would try to turn the head. And if I held it in long enough, would get it going. My problem was one of the legs on the starter was wired to the leg coming off my RPC, I moved the RPC leg off the starter and put the two legs from the house on the starter and the RPC on the third leg. Reversed the motor, but that was easy to fix at the motor.

I really hope that makes sense because I'm really stupid when it comes to sparky things. I had a bit of help from a guy here at work that got me up and running (meaning he drew me a diagram and told me exactly how to hook it up). How I see 3 phase is you have 3 legs of power, 2 from the house at 120 each and then a manufactured leg off your phase converter. But my starter only run off 2 of the 3 legs, not sure if there's any that run off of 3 legs. So somehow 3 legs of 120 equals 240 3 phase. Still haven't figured that one out in my head...

[David Kumm]

You generally want to avoid running a coil with the manufactured leg of an RPC, especially an older or unbalanced one. The voltage to ground is likely to be high and casue a bunch of problems. The PP doesn't have that issue. I talked to tech support at SCMI and the guy said that somewhere between the transformer and the coil I was losing voltage as the problem sounds like 115 volts at the transformer was probably 80-90 at the coil. It could be be contacts in the stop button NC or even the main on-off module. My meter was out of calibration which I fixed by blowing it up so I'm off to get a new meter for testing tonight. Dave

[Stephen Cherry]

You generally want to avoid running a coil with the manufactured leg of an RPC, especially an older or unbalanced one.

Very true.

The box on the lower right looks like a thermal overload/ and disconnect; I would guess there is an on/off knob on the outside of the door that matches up with this. Normal US wiring would be disconnect- contactor, overload, though.

The first thing I would do is bop in the contactor with a screwdriver and see if the motor starts, if yes, it would indicate a control issue. if the thermal overload trips, turn them up a little. if they still trip, assuming you have short circuit protection somewhere, I personally would wire around the thermal overload FOR TESTING ONLY. I WOULD NOT CUT WOOD LIKE THIS. Then you will isolate the thermal overloads.

Can you post pictures, schematics?

[David Kumm]

Stephen, I've done as you suggested. I bypassed the breakers-25 amp- and wired the leads into a 30 amp fused disconnect for testing. Saw started but the coil still didn't engage the magnets properly. Couple of hits and then stayed in. I can push the starter manually- I use a stick- and it starts fine. Will check voltage to see if there is a drop between the transformer and coil tonight. Dave

[Stephen Cherry]

Stephen, I've done as you suggested. I bypassed the breakers-25 amp- and wired the leads into a 30 amp fused disconnect for testing. Saw started but the coil still didn't engage the magnets properly. Couple of hits and then stayed in. I can push the starter manually- I use a stick- and it starts fine. Will check voltage to see if there is a drop between the transformer and coil tonight. Dave

Used a stick and it started- that's good, Does it seal in the start with the aux contact once pushed in? What is the coil voltage- 110, 220,? Maybe try replacing the control transformer with an extension cord pluged into an outlet.

Have you tried pulling on all wires, etc? I can't tell you how many times I have trouble shooted down to a connection that is not tight.

[Stephen Cherry]

Also, you may want to try wiring out any interlocks, if present, in the start wiring. Just for testing purposes. (doors closed, etc)

[David Kumm]

Update. Turns out to be a transformer problem. Although it tested at 124 v it evidently doesn't produce enough current to operate the bigger starter. I took Rod's suggestion and rigged up a bypass to an extension cord and all is well. Good news is everything runs well, bearings sound good and worse case scenario is a $50 fix. My question is whether to replace the transformer since using one leg would mean I need to use the ground as a neutral. Am I correct in assuming the transformer somehow creates a substitute neutral or does it also go directly to ground? I don't want to sort wires to try to figure it out if i can get advice. Second question is should I upsize the transformer. The current one is a SQ D 9070 E 03 ser B .150KVA. Thanks for all the help. I've learned a lot about euro electronics during this process. Dave

[Leo Graywacz]

A transformer is an isolation device if you use it as a primary secondary device. If the primary is connected to the secondary (as a buck/boost transformer) then there is no isolation.

Where is the transfomers primary connected in the circuit? On two hots or on a hot and a ground or neutral? If there is a transformer in there I would assume it is used to take the 230 (208?) down to 120vac. In that case there is no neutral/ground issue. You could also swap out the coil for one that has the proper primary voltage of the source and eliminate the transformer completely.

[David Kumm]

A transformer is an isolation device if you use it as a primary secondary device. If the primary is connected to the secondary (as a buck/boost transformer) then there is no isolation.

Pardon me for being stupid but I don't know what that means. The transformer allows this machine to be wired 230 or 460 without changing any electronics other than the transformer leads. I don't have a neutral going to the machine and don't know if eliminating the transformer means I would use the ground as a neutral. I've done that with some smaller machines with a 120 coil but it isn't ideal. Am I better off replacing the transformer or bypassing and using the ground as a neutral. Dave

[Leo Graywacz]

Be safe and replace the transformer.

[David Kumm]

Be safe and replace the transformer.

I'm happy with that advice. Any advantage or downside to replacing the .150kva with the identical model with .250kva? New old stock on ebay is actually cheaper than the .150 one. Thanks, I so appreciate the help. Dave

[Leo Graywacz]

Unless the old one was defective or undersized I find it strange that a transformer would have problems. They are extremely dependable devices.

Going with a larger rated model will have no effect on operation. If it supplies the correct voltage and enough current then it will do well. Nothing wrong with a little bit of extra headroom.

[David Kumm]

Unless the old one was defective or undersized I find it strange that a transformer would have problems. They are extremely dependable devices.

Going with a larger rated model will have no effect on operation. If it supplies the correct voltage and enough current then it will do well. Nothing wrong with a little bit of extra headroom.

Since it is a sq D on a saw with all Klockner Moeller electrics I wonder if it was replaced. Dave

[Leo Graywacz]

I would guess that it was. That would mean the one you replace it will be the third one that is going in there. There might be another problem lurking in there. If it does go out again you might want to replace the contactor.

[Kevin W Johnson]

Could be that the transformer that's on there now can't supply the needed current. If someone did indeed replace it before, there's a good chance they didn't replace it with the proper unit. A transformer that can supply more current sounds like a plan.

[Rick Fisher]

David ..

If the transformer is being used to reduce the voltage during start up .. which at 124V sounds about right, then it needs to be replaced with the same transformer..

By reducing the voltage, you reduce the need for current but give up torque. That causes the motor to sound like it " winds up " to speed. It gets to speed without the big inrush and developing huge amounts of heat ..

It wont supply full amperage to the motor because it was only ever designed to supply about 40% - 45% of FLA ..

After the motor reaches speed, ( or after the timer ticks ) .. the transformer would be removed and the motor voltage would jump up to 230V . ( Delta ) ..

Then the motor would be able to draw FLA .. and have 100% torque..

In that circumstance, there could be a resistor in the starter that keeps the voltage stable during the transition from running through the " Auto transformer " and running full voltage.
They don't always use a resistor but at this point you should find out ..

Its called a reduced voltage starting system and its either open or closed.. Closed uses a resistor and is much less likely to trip during start up .. ( so if a resistor failed, tripping could be a problem ) I wonder .. did it start up fine after not being used for a while, and then act up ?

It could be that the transformer was changed, but it didn't fix the problem, so they sold the saw .. If the starter uses a resistor to stabilize the voltage during transition, that resistor needs to short itself out after each start up.. That alone would make it fussy to start ..

Or it could be the transformer is busted for the second time .. Square D is not the stock part ..

The transformer in mine is made by Busto .. Everything else ( Moeller) is the same.. I would assume Busto SPA made the stock one for your saw too ..

Anyway .. I would check with SCM .. Ask if there is a resistor you could test .

You know .. you can avoid all this by putting a drive on the saw.. It would need to be a 10hp model.. It wont be long before all this stuff is history and motor drives are the norm..

[Leo Graywacz]

Pretty sure that the transformer he is referring to is only a voltage adjusting device to give the contactor coil the 120vac it requires to operate properly.

[David Kumm]

Pretty sure that the transformer he is referring to is only a voltage adjusting device to give the contactor coil the 120vac it requires to operate properly.

Leo, i think you are correct. the saw is from the 1980s and doesn't have as much electronics as my later machines. I will say that in my history of buying old and fixing up that many poorly performing old machines seem to be the result of crappy replacement parts installed previously. Woodworkers generally aren't machine guys and I've gotten great stuff that the seller- being less than forthright- sold reasonably because he thought the machine design was bad. Bearings that were right size but wrong for the application, missing set screws, ways out of adjustment, little parts that serve more purpose than what their size infers, etc. Good and bad for me. Takes time but the learning is fun- after you succeed. Failure sucks. Dave

[joe milana]

I'll assume I'm not the only one that has followed this thread with a vested interest, and am amazed at how complicated it has to be just to turn an electric motor on & off. My focus is on the business end of these machines, but I really should know a bit more about why all the electronics is necessary, and would like to know more. I'll assume a lot of it is for safety reasons?!?

[David Kumm]

I'll assume I'm not the only one that has followed this thread with a vested interest, and am amazed at how complicated it has to be just to turn an electric motor on & off. My focus is on the business end of these machines, but I really should know a bit more about why all the electronics is necessary, and would like to know more. I'll assume a lot of it is for safety reasons?!?

The newer machines are even more complicated. Soft start, electronic injection brakes, etc. Euro stuff has a lot of safety mandates. I'm used to the old US starters with a heater for each leg. The euro machines use an overload for each motor and one for the transformer so they are a whole different animal. I know SO little but every problem creates some knowledge. As the years go by those of us who like high end used will have to get better at the electrical part. If something craps out on my old stuff I just replace a starter, coil, heater whatever and am good to go. I still carry a lot of electrical inventory but nothing like what will be needed for euro machines. Dave

[joe milana]

So what I've interpreted from this thread, basically for the simplest of machines, a transformer gets power from one of the incoming lines and provides 110v to the power switch, which sends current to a coil , which moves a magnet (somewhat like a solenoid valve on a washing machine) which closes a contact and allows the motor to run? An overload lies somewhere along the line and acts as a breaker in the event of, well, an overload? :confused:
If I'm way off, don't bother answering, and I'll shut up and go make sawdust, hoping my machines fire up...;)

[Leo Graywacz]

Nope, you've got the jist of it.

[Rick Fisher]

Seems odd .. Why would they not have just installed a 230V coil.. ? Its more expensive and more parts to install an undersized coil .. ??

Weird stuff ..

[Van Huskey]

Seems odd .. Why would they not have just installed a 230V coil.. ? Its more expensive and more parts to install an undersized coil .. ??

Weird stuff ..

Two things come to my late night, beer hazed mind, which I am sure are both incorrect. 1. could there be a requirement in Europe to only have 120V going to the actual switch, though not by regulation but Northfield has 120v switches on their 240/440 machines and it is mentioned as a "safty feature" 2. could it be that it makes a 240 to 440 switch easier since maybe the transformer has multiple taps so you could just switch taps and get 120v out from either voltage in? In the end on the off chance either one of my thoughts are correct I would think #1 stands the best chance. All in all the fact I think it is over-complicated probably means I don't have a clue to understanding the big picture, then again it wouldn't be the first time an engineer in central Europe over-thought things...

[David Kumm]

Van, #2 is correct. The transformer allows the machine to run on many voltages without changing the electrics other than the leads on the transformer. All the other modules are multivoltage or thermo breakers. 220,440,380,600 etc. Dave

[Rick Fisher]

I woke up this morning thinking about this thread .. something is not connecting inside my simple brain.. lol

A 120V coil would need a neutral, not a transformer .. What would you transform the power from a single leg 220V into ? A single leg of 220V is 110V if connected with a neutral, its not transformed ..

David... could you post a pic of the whole set-up ?

[David Kumm]

I woke up this morning thinking about this thread .. something is not connecting inside my simple brain.. lol

A 120V coil would need a neutral, not a transformer .. What would you transform the power from a single leg 220V into ? A single leg of 220V is 110V if connected with a neutral, its not transformed ..

David... could you post a pic of the whole set-up ?

Rick, hopefully more knowledgeable will post but my understanding is the transformer also serves as a neutral in this case. Since there is typically no neutral in commercial three phase wiring the other choice is to use the ground as neutral. I don't know if the transformer eventually goes to ground but it somehow serves as the neutral. On my old machines I try to avoid a 110 coil because I don't like using the ground. Dave

[Leo Graywacz]

The secondary on the transformer is isolated from the system. The ground has to come from the chassy of the machine.

[Stephen Cherry]

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/td03309004e.pdf

The transformer should go L1 to L2 of the supply voltage. One leg of the output is grounded so that it does not float; if you don't ground one side, who knows what voltage will be induced with respect to ground. The grounded side is effectively the neutral, with the other side the hot.

and the whole idea is to keep potentially high voltages away from the buttons, etc. It's always much nicer to get zapped with 120v.

[David Kumm]

As a final follow up on my starter problems it turns out L1 and L3 were mislabeled in the box so I was running the manufactured leg into the transformer. 240 checked out fine but the voltage to ground on the mfg leg caused transformer problems. Didn't shop up when testing- thats my story and I'm sticking to it- but had i been a little brighter I would have diagnosed it faster. My transformer inventory is now a little deeper but I lost more sleep than money. I had believed the mfg leg wasn't as wild on the PP but found out that assumption was in error. Dave

[joe milana]

I thought PP was balanced to <1%.

[David Kumm]

I thought PP was balanced to <1%.

It is balanced leg to leg but leg to ground is high on the third leg. Had I read the manual carefully it would have been obvious. I'm a huge PP fan though. I have three of them- all used. Dave

[Van Huskey]

Glad to hear you got it all figured out! I am sure that was VERY frustrating.

[David Kumm]

There's no cure for Dumb. Dave

[Leo Graywacz]

There's no cure for Dumb. Dave

That should be

"You can't fix stupid" :rolleyes:

[David Kumm]

That should be

"You can't fix stupid" :rolleyes:

I forgot one of my rules when dealing with used. Never assume the bearing you are replacing was the correct one, nor the starter, nor anything else. Assume everything has been modified incorrectly. Dave

[Van Huskey]

I forgot one of my rules when dealing with used. Never assume the bearing you are replacing was the correct one, nor the starter, nor anything else. Assume everything has been modified incorrectly. Dave

Thats a very good "rule" I have a bad habit of assuming what is there is correct and probably fall into this bad habit more often when it has to do with wiring, mainly since I assume most people know more about wiring machines than I do. I will have to keeo this in mind!

[Adam Neat]

David it sounds like youre either missing a phase on your power or the motor is opened up on one phase.

When a 3 phase motor looses a leg it will have trouble starting. The rush of current when it tries to start is probably whats kicking your overloads (on the 2 legs that are good)

If it were mine I would disconnect the motor and make sure I had voltage on all three leggs coming out of the starter.

If thats good look at the motor, I assume its wired for the correct voltage?

Take an ohm meter to the motor leg to leg. You should get a very low ohm reading, just a few ohms, and all three should be almost identical.

Then check each to ground, you should read open or at least in the meg ohms

[Rick Fisher]

David..

Could you explain that again about the wild leg on the PP .. Maybe use smaller words for me .. lol..

When I test mine, leg to leg, I get 240,240,242..

Your saying if I test it to ground, I will get 120,120, ???

I can grasp that, but how did it cause your problem ? Was the Hot to ground voltage off so much that it caused the coil to now engage ?

[Adam Neat]

Sorry I bumped this up with some erroneous reply. New to the forum and was only seeing one page:o Now I see there were 4, now 5 pages :eek:

Anyway glad you got it sorted out

[David Kumm]

Rick, I don't understand enough myself to give a coherent explination. A RPC or even a PP will check out 240 across any two legs but the manufactured leg will have high voltage when checked to ground- the wild leg. I don't know why that affects a transformer but it does. I know from experience you don't want that leg to go to a coil or even worse a vfd. In my case the wires in the box had little numbered rings and the L1 and L3 had been reversed sometime in the past so I was using the wild leg with the transformer. It made the coil act like it didn't have quite enough voltage to engage even though it checked out at the transformer. I've had lots of experiences where the meter seems to test until under load but I don't have a clue as to why. Dave

[joe milana]

Interesting, because I'm sure I've read on more than one thread that if a three phase machine runs in reverse, simply switch any two of the power leads.

[Van Huskey]

This thread could prove darn useful for someone in the future. Pulling a machine that has been fiddled with off "true" 3ph power would work fine there but cause these issues which could drive someone crazy if they never thought to check this or even knew the manufactured leg was actually "different".

[David Kumm]

Joe, switching any of the three leads is fine if wiring between the starter and motor. If the power is before the electronics you can only switch between L1 and L2 or what happened to me will happen to you. Dave

[Rick Fisher]

Thanks for the heads up on that David.

Both my Jointer and Edge Sander have power contacts at the base of the machine.. ( before the switch ) .. Both ran in reverse when wired.. I swapped 2 wires and both worked. I now believe I got lucky ... :)

Unless both had 240V coils in the starters ??

Glad I know this now ..