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  1. #361
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    We need to talk.

    The contacts in the afore photograph contactor are fine, don't dress them or do anything to them other than blow off dirt.

    Why do they look bad? Most people would look at the rough surface and say those those are burnt, file them down so they are nice and smooth and shiny. All that does is to throw away silver. It does NOTHING to improve the contact.

    When contacts close, they bounce around for a few milliseconds. Ya know, the old spring, mass, momentum and dampening routine. Strike an anvil with a hammer(not dead blow) and it bounce. Same thing with contacts. They hit and bounce open and reclose and bounce open again until the energy is absorbed. Each time they do that they draw and arc which melts a small amount of silver. When the contacts close on the molten silver, they weld. The weld is pulled apart on the next bounce open and so on. The results are very rough ragged surface. When this happens on a edge, the silver is mushroomed over and looks like the top of a chisel. Finally, the contacts quit bouncing, and guess what, the contacts are actually welded together.

    The current on starting the motor is high, usually 6x the FLA. There is a lot of energy to form those welds.

    On breaking of a set of contacts, the current is normally much less than the inrush and the power factor is usually high, .8 to .9, normally. The recovery voltage is nearly at the same angle as the current wave, meaning that the tendency to restrike is low.

    Getting back to the now welded contacts, when the coil is released, the potential energy in the springs and gravity will break the welds and in so doing will cause an arc to form. The energy in the arc is comparatively low and because of the high power factor, the arc will only last for less than a half cycle. But if one were to look at the contacts carefully, there will be a small molten and solidified spot where the last contact was made.

    Because there are many more bounce open arcs than breaking arcs, the resulting surface is ragged looking.

    Newer design contactors have much less bounce and thus show less of this behavior, but is still there.

    Let's look at the contacts referenced in Thermite's reply

    Top left stationary contact looks normal, the arc has moved off the contact smoothly. Top right contact shows "ridge" on the right edge. That's not good, that contact has seen a lot of rocking on closure and very little arcing on break.

    The "good" moveable left side shows normal making erosion and excellent arc management. The arc has moved off the silver and on to the copper arc horn very quickly. One the other end there is very little arc erosion and mainly just contact bounce. This contact did not close uniformly, it "rocked" in, making contact on the right, then the left. Same on opening.

    The stationaries of the damaged contacts do not look bad at all. However, the moveable is a different story. This contactor was cycled rapidly leading to heat buildup. There is significant erosion of the left contact with small chunks of silver gone. The right side appears to been heated to the point the braze has softened and allowed the silver to shift to the left.

    Tom

    Edit: In the panel next to the one discussed above is another set of "good" and "damaged" contacts. THERE IS ABSOLUTELY NOTHING WRONG THE "DAMAGED" CONTACTS. They have seen normal operation. Anybody tries to tell you that those contacts are bad and should be replaced is NOT your friend.

    T:-

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    Quote Originally Posted by TDegenhart View Post
    We need to talk.

    The contacts in the afore photograph contactor are fine, don't dress them or do anything to them other than blow off dirt.

    Why do they look bad? Most people would look at the rough surface and say those those are burnt, file them down so they are nice and smooth and shiny. All that does is to throw away silver. It does NOTHING to improve the contact.

    When contacts close, they bounce around for a few milliseconds. Ya know, the old spring, mass, momentum and dampening routine. Strike an anvil with a hammer(not dead blow) and it bounce. Same thing with contacts. They hit and bounce open and reclose and bounce open again until the energy is absorbed. Each time they do that they draw and arc which melts a small amount of silver. When the contacts close on the molten silver, they weld. The weld is pulled apart on the next bounce open and so on. The results are very rough ragged surface. When this happens on a edge, the silver is mushroomed over and looks like the top of a chisel. Finally, the contacts quit bouncing, and guess what, the contacts are actually welded together.

    The current on starting the motor is high, usually 6x the FLA. There is a lot of energy to form those welds.

    On breaking of a set of contacts, the current is normally much less than the inrush and the power factor is usually high, .8 to .9, normally. The recovery voltage is nearly at the same angle as the current wave, meaning that the tendency to restrike is low.

    Getting back to the now welded contacts, when the coil is released, the potential energy in the springs and gravity will break the welds and in so doing will cause an arc to form. The energy in the arc is comparatively low and because of the high power factor, the arc will only last for less than a half cycle. But if one were to look at the contacts carefully, there will be a small molten and solidified spot where the last contact was made.

    Because there are many more bounce open arcs than breaking arcs, the resulting surface is ragged looking.

    Newer design contactors have much less bounce and thus show less of this behavior, but is still there.

    Let's look at the contacts referenced in Thermite's reply

    Top left stationary contact looks normal, the arc has moved off the contact smoothly. Top right contact shows "ridge" on the right edge. That's not good, that contact has seen a lot of rocking on closure and very little arcing on break.

    The "good" moveable left side shows normal making erosion and excellent arc management. The arc has moved off the silver and on to the copper arc horn very quickly. One the other end there is very little arc erosion and mainly just contact bounce. This contact did not close uniformly, it "rocked" in, making contact on the right, then the left. Same on opening.

    The stationaries of the damaged contacts do not look bad at all. However, the moveable is a different story. This contactor was cycled rapidly leading to heat buildup. There is significant erosion of the left contact with small chunks of silver gone. The right side appears to been heated to the point the braze has softened and allowed the silver to shift to the left.

    Tom

    Edit: In the panel next to the one discussed above is another set of "good" and "damaged" contacts. THERE IS ABSOLUTELY NOTHING WRONG THE "DAMAGED" CONTACTS. They have seen normal operation. Anybody tries to tell you that those contacts are bad and should be replaced is NOT your friend.

    T:-
    Right.

    "Friend?" Those major makers don't even know my name. They DO know their products.

    So Matt is making it all up.

    His contactors work just bitchin' fine? Guess he just hasn't seen your "rapture" yet?

    You wanted to make a point, the damaged contacts were but the dead bones. Their real-world, not theoretical, FUNCTIONAL FAILURE was the hard evidence, yah?

    Matt's an inquisitive guy. Always learning. Mayhap he'll be willing to try carrying the current on your opinion instead of Silver-Cad?

    These are overdue for replacement, and on multiple grounds. Disregard that? Endure the grief.

  3. #363
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    Quote Originally Posted by thermite View Post
    Right.

    "Friend?" Those major makers don't even know my name. They DO know their products. Do they?

    So Matt is making it all up.

    His contactors work just bitchin' fine? Guess he just hasn't seen your "rapture" yet?

    You wanted to make a point, the damaged contacts were but the dead bones. Their real-world, not theoretical, FUNCTIONAL FAILURE was the hard evidence, yah?

    Matt's an inquisitive guy. Always learning. Mayhap he'll be willing to try carrying the current on your opinion instead of Silver-Cad?

    These are overdue for replacement, and on multiple grounds. Disregard that? Endure the grief.

    Not quite true. Hoyt is a major replacement contact manufacturer. There others but I know nothing about them. Case in point. Hoyt makes replacement contacts for GE controls. They are not the same, at least as of the last time I studied them. I lead the development of contact attachment for the 300 line of control. The process is percussion welding. It is not something that one can pick up and start using. This process allows for up to 30% additional silver utilization over brazing. Second item is the silver alloy. There are two methods of making silver cad oxide, internal oxidation and powder metallurgy. The powder metallurgy products are inferior to the internal oxidized material in every test I ran.

    As to Matt's contacts, You, sir, are making grave assumption that the contacts are the root of his problem. In fact you suggested that the coil voltage was not correct. Right now I believe that too. But the contacts? No.

    Explain to me in DETAIL, why you feel the contacts have failed.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    Explain to me in DETAIL, why you feel the contacts have failed.

    Tom
    I don't HAVE to explain, Tom.

    The contactor has already done that for us.

    Have Matt put it on the phone, willyah?

    Talk it out of its troubles.

    Don't tell ME - I use Crydoms and Mercury-Displacement contactors. I haven't had this problem "personally" since 1973. I'm good with the Mercury until the world turns upside down.

    Its the truant contactor you have to convince it is only faking an illness as an attention-bid!

    Good luck with that!

    You think I'm an obstinate Old Fart? Try convincing a contactor that's even older yet. Sore tired, too. Probably worked harder than I had to do.

    Nothing, nor no one, lasts forever. We are ALL "due for replacement" in the fullness of time...


  5. #365
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    Coils are 220/208V, I think it's both coil and contractors, both smoke spark and get hot. Motor stars with tremendous electrical noise, clattering from the starter and can only get to about half speed. I wired it straight into the breaker, and it stars and runs great.

    Considering that a Chinese 25hp starter (that's supposedly decent quality) is 170 bucks, I'll probably end up replacing it.

    I was merely asking for education purposes and in the hopes that a file and emery cloth would save me 170 bucks.

    I put a meter on this beast when I started it up, it drew 280 amps on start up, and 30 when at no load. No wonder the power company keeps slapping me with high demand charges....

    Also found a better turning tool and started to do some accuracy tests, (sort of, not really), over about 6" the lathe was making about .0001 taper, I was impressed. Guess there is something to be said about mass and a very wide carriage.

    Next I'm going to see what it does at larger shaft lengths.

  6. #366
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    So if you do not use them then you are in no position of criticizing their functionality. Judging from the design of the contactor, those are not silver cad. Probably silver iron.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    So if you do not use them then you are in no position of criticizing their functionality. Judging from the design of the contactor, those are not silver cad. Probably silver iron.

    Tom
    I knew enough about them to write the manuals.

    Why do you think I sought-out solutions that didn't HAVE external arcs nor a contact-life problem AT ALL?

    Original designs, I could make the choice, and did.

    My own equipment, I could make the choice, still do.

    "Company" equipment, I could only approved a PO for NEW. Dominant-carrier / monopoly Telco's don't "do" a lot of rebuilds. Too much at stake when some circuits are permitted all of two seconds unscheduled downtime in a whole YEAR!

    Old Iron, I revere.

    Old electricals? Not so much.

  8. #368
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    Quote Originally Posted by alskdjfhg View Post
    Coils are 220/208V, I think it's both coil and contractors, both smoke spark and get hot. Motor stars with tremendous electrical noise, clattering from the starter and can only get to about half speed. I wired it straight into the breaker, and it stars and runs great.

    Considering that a Chinese 25hp starter (that's supposedly decent quality) is 170 bucks, I'll probably end up replacing it.

    I was merely asking for education purposes and in the hopes that a file and emery cloth would save me 170 bucks.

    I put a meter on this beast when I started it up, it drew 280 amps on start up, and 30 when at no load. No wonder the power company keeps slapping me with high demand charges....

    Also found a better turning tool and started to do some accuracy tests, (sort of, not really), over about 6" the lathe was making about .0001 taper, I was impressed. Guess there is something to be said about mass and a very wide carriage.

    Next I'm going to see what it does at larger shaft lengths.
    Sounds like a bad coil(s). Time to replace.

    One last test before you spend $170. Make sure the coil is connected to the transformer legs and not to the generated leg. The generated leg is unstable during starting, voltage will drop to values that the contactor won't operate properly.

    Tom

    PS what is your shop voltage 200, 208, 230.....?

  9. #369
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    Quote Originally Posted by alskdjfhg View Post
    Considering that a Chinese 25hp starter (that's supposedly decent quality) is 170 bucks, I'll probably end up replacing it.
    An OEM one, NOS, is probably twice that. To be fair, it could also have twice the longevity - as your one shows. OTOH, new is new, and it will probably be many years out before you have to worry about that.
    I was merely asking for education purposes and in the hopes that a file and emery cloth would save me 170 bucks.
    I've probably still got special files and diamond-coated goods (no actual "emery" wanted!) for that around, but it isn't WORTH it.

    There's other wear, age effects, and damage, not just the coils and contacts.

    A TENTH of taper, as-had!

    S**t!

    Go BBQ a goat in thanks!



    Our worst old Niles had thirteen-thou of taper in its "bad spot". Didn't stop 3 shifts a day of us making decent bearing fits on shafts for long years. Yah just worked around that- used a different lathe when one could not.

    Card-carrying USWA Machinists came and went. Our three shift foreman had come up through those ranks. By aged forty to sixty, each of them knew every flaw in every machine in the hall, klewed us in. They HAD to know that stuff. WE only had to know what to do about it.

    Your turn, now! Both roles, fast-learner!


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    Allan Bradly used starters on E-bay!

    Your old Yankee iron will likely "reject" the Chinc replacement part after a while.
    (or we can all hope!)


    ---------------------

    Think Snow Eh!
    Ox

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    Quote Originally Posted by Ox View Post
    Allan Bradly used starters on E-bay!

    Your old Yankee iron will likely "reject" the Chinc replacement part after a while.
    (or we can all hope!)


    ---------------------

    Think Snow Eh!
    Ox
    Or SqD, Cutler-Hammer or GE (300 line). If you go with any of these then you will need a NEMA size 3 starter. I would avoid Westinghouse and Furnas or any of the other odd ball brands. GE 100 and 200 line starters work fine electrically, but tended to fall apart mechanically, mainly the magnets. European would be Siemens, ABB among others. Bear in mind that if you go with a European starter, you will have to use their application charts to get the correct size.

    Tom

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    If I recall correctly, you are using a rotary phase converter to power your equipment? Make sure the power for the coil is not coming from the generated leg, I have had contactors behave like you are describing when the generated leg was used to power the contactor coil.

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    I think I still have this if it would work for you... I can take it out of the plastic for better pics if you need me to. It would be real cheap..
    Attached Thumbnails Attached Thumbnails 0624141645.jpg   0624141645a.jpg   0624141648a.jpg   0624141649.jpg  

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    Quote Originally Posted by homanfab View Post
    If I recall correctly, you are using a rotary phase converter to power your equipment? Make sure the power for the coil is not coming from the generated leg, I have had contactors behave like you are describing when the generated leg was used to power the contactor coil.

    Actually - I have a 50hp compressor that I had to pull the start circuit off of the buss line and put it on a wall plug on our current RPC line. The starter would pull in, the motor would pull the V down, the starter would drop out and repeat as long as you held the start button in.

    Put the starter on the wall plug and it werks fine now. (seldom to never run it tho)


    -------------------

    Think Snow Eh!
    Ox

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    Furnas brand starters are also very good US components.

    I love the crusty Chinese starters with no brand name that just say "Siemens License". They musta forgot to license the part that lasts more than a few hundred starts.

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    If you don't buy a NEMA sized starter double or triple size the starter for your HP.

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    Quote Originally Posted by ewlsey View Post
    Furnas brand starters are also very good US components.

    I love the crusty Chinese starters with no brand name that just say "Siemens License". They musta forgot to license the part that lasts more than a few hundred starts.
    Yes and no. I worked for Furnas for 7 years on their contactor line. Their DP'S are very good, PB's and OL's same, but the INNOVA line had issues. One is if the coil burns out, the starter has to be taken apart to get it out. The coils were not well designed or built and had frequent coil problems. The green molding compound was granular polyester that is of low strength and wore quickly.

    Even though the INNOVA was designed to be a NEMA class starter, it was really better at applications small, low usage machines, not heavy industrial equipment.

    The last task I had there was a complete new design size 4 to replace the old vertical lift. I was able to correct the deficiencies of the old INNOVA.

    I get a chuckle whenever I think of the electrical short circuit test I had the lab run. Maximum station current and voltage closing on a dead short, both the new design and the INNOVA old design. Old design flew apart, new design still functional, passed high pot. When the test was run, all the lights in building dimmed, there was loud Whomp! and smoke filled the lab. Gill Nary the controller came running down to see if we had set the lab on fire. We hadn't. Rumor was that whoever burnt down the lab was the new engineering manager. I lost.

    Tom

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    Quote Originally Posted by ewlsey View Post
    I love the crusty Chinese starters with no brand name that just say "Siemens License". They musta forgot to license the part that lasts more than a few hundred starts.
    Phht.. Hong Kong, Chinese makers were selling the Hell out of useless fluorescent ballasts - prolly made of scrapped bean-tin reject sheet for as hot as they ran.

    Label said simply" "German Type". Sometimes they'd last a whole YEAR!

    Meanwhile the tubes leaked so much UV at the poorly coated ends all the equally shitty plastic wiring jackets would crumble and fall off the wire.

    Finally cruised down Lockhart Road, bought top-end German imports.

    Those ones haven't set a foot wrong yet, 20 years in the hot and humid kitchen.

    China IS making some decent 'lectrical stuff NOW. But it took 20-30 years, and you STILL have to watch really close which is what.

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    I think I'm going to be making a trip to an industrial surplus place to get a transformer next week.

    When I do that, I'll see if they got a motor starter the size I need.

    Mcgyver, that looks like it would work. I might be interested.

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    Just let me know, I will try and remember to dig it out. I am pretty sure that is the biggest size I have, might have some 50 amp ones as well if you think you might need one for something else.


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