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  1. #21
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    Quote Originally Posted by Vladymere gr View Post
    Beansdiesel,

    Why such a large RPC? What are you running that requires 100 amps of three phase power? Would a smaller RPC be appropriate?

    Vlad
    Covered in an earlier PM thread. JST linked to that already.

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    Quote Originally Posted by JST View Post

    SAF:

    What do you think of that spec of 13.6A idle current for the RPC? If so, that is the losses, and I would tend to believe in 5% mechanical losses and iron losses as at least credible (about 4 HP out of 75).

    Without any correction, I would expect a motor with 190A FLA to pull around 60A at idle, most of which is reactive current. Then the power factor caps need to compensate out 12 kVA of reactive current, and the caps which you think (and I agree) are the PFC caps appear to be 8 or 9 kVA worth... Reasonably possible, I'm just guesstimating at the idle reactive current..

    "Originally Posted by beansdiesel

    I got the quote back, having the SS and a better cap setup with a new wall mounted box sounds nice and all, but I don't want to spend that much.

    The transformer is a 15kva and we are the only one on it.

    Him saying the Cap setup wasn't good enough for CNC has me worried about it. Is there a way to just add more caps or change them out to better ones?"
    Reviewing the Starting, Idling, Reactive Current and Cap Setup

    In my area the line voltage usually runs on the higher side, so I would expect to see the idle/reactive current be much higher than the 13.6A listed, as the iron becomes magnetized stronger. Can be as much as 1/2 FLC on an uncorrected motor. Then given the earlier fact, that the unit was shipped in 2011, That tells me, that the motor is an EPACT energy efficient model with the much higher inrush starting current. Higher efficiency at the cost of increased start current.

    The idle current with correction on the current model of this size is listed at 25A @ 96PF found here:
    Remco Electrical Manufacturing | Phase Converters

    So even the builder has upped the idle current spec by a factor of almost 2. In some field conditions that could be higher. Given your suggested value of 9KVA worth of PF correction that is approaching the 15KVA value of the service in question.

    After reviewing the photos in the original post, there appears to be NO power factor correction connected!! L1 & L2 are the line terminals and L3 the generated terminal. Viewing the reworked capacitor terminations it appears that what used to be the PF bank has been re-purposed as part of the phase shifting bank. Leaving the RPC uncorrected. This I believe would leave the unit drawing around or above the 12KVA figure given above, again close to the FLA capacity of the service.

    It appears that some additional #12 AWG conductors, GRN & YEL, were added to parallel the runs to the bank rows and that the OEM, BLK conductors were also paralleled to make up the other half of the paralleled set. All cap bank leads are connected to T2 & T3. So it appears that the modification to give better CNC capability to the unit as suggested by the OEM, has left the unit with no power factor correction and drawing some serious reactive current during idling.

    There is some serious oxidation on the components in that enclosure. The aluminum terminals, the steel cap cans, and the tin plated cap tab terminals. Looks to be due to condensation from an unheated environment and no ventilation in the enclosure. Those spade terminals I consider only good for about 10A max and 7A if used under continuous load. With them so oxidized I would consider them very unreliable as did the OEM. For the kind of service here I would be putting separate leads on each cap. Appears that that has been already partially done by paralleling due to field failure, but not completely.

    If I were going to replace them as an upgrade I would be looking for units with stud terminals, for a more robust and reliable connection, for this type of service. Especially since they are attached inside an enclosure affixed to a vibrating motor.

    As a side note on those oxidized cap cans. Notice how the top sections are less oxidized? I would surmise that the top of the cans were heated due to the connection resistance, driving off any accumulated condensation sooner than the rest of the can.

    For a different method of a start test, I would reconnect the small bank as the PFC use and disconnect the phase shifting bank. That would reduce inrush and maybe allow it to get started on the limited means available and get some actual current readings to base any further alterations on♦

    SAF Ω


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    Quote Originally Posted by SAF View Post
    I would suspect the bi-metal element being out of calibration from his repeated attempts to use it as a starter for a DOL 75HP motor.
    He keeps saying "Trips the breaker, trips the breaker ..." I swear, those things won't live if you treat them like that. Not that I have any experience burning up breakers or anything but ....

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    Post a video when you get it running.

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    Quote Originally Posted by Shawn Ghormley View Post
    Post a video when you get it running.
    Don't know much about you, Shawn. But I shall hazard a guess.

    You are one seriously PATIENT individual, are you not?

    ...or is it just an optimist?


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    SAF:

    Good eye... I totally missed that about the repurposing, but as soon as I read your comment and looked, it was perfectly obvious.

    The other reason for the tops being less corroded may be due to the caps warming up in use, and the heat rising to the top, so that the top had less condensation.

    In my experience, the spade connectors, if tight and properly assembled to begin with, not disturbed and not overloaded, tend to produce a good connection over time until they get really corroded.

    But that varies. if overloaded so they heat up, they relax and are terrible. Same if some person has trouble getting them installed and decides to "relieve the pressure". or gets them cocked putting on, so the female half is stretched open, And then there are 0.020 and 0,032 versions of them. The wrong connector thickness combo will be loose, or so tight that the female half is distorted when put on and soon becomes loose.

    The bad rep is probably as much or more from screwups assembling as it is from real problems. At a former employer we used millions of them, and had very little trouble.

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    Quote Originally Posted by JST View Post
    SAF:

    Good eye... I totally missed that about the repurposing, but as soon as I read your comment and looked, it was perfectly obvious.

    The other reason for the tops being less corroded may be due to the caps warming up in use, and the heat rising to the top, so that the top had less condensation.

    In my experience, the spade connectors, if tight and properly assembled to begin with, not disturbed and not overloaded, tend to produce a good connection over time until they get really corroded.

    But that varies. if overloaded so they heat up, they relax and are terrible. Same if some person has trouble getting them installed and decides to "relieve the pressure". or gets them cocked putting on, so the female half is stretched open, And then there are 0.020 and 0,032 versions of them. The wrong connector thickness combo will be loose, or so tight that the female half is distorted when put on and soon becomes loose.

    The bad rep is probably as much or more from screwups assembling as it is from real problems. At a former employer we used millions of them, and had very little trouble.
    I have had miserable experiences with them. Some of the locomotive equipment has them and after a few years in a Diesel engine compartment, they are so dirty that the only place where they can make a good connection is the tiny protected surface where the connector kept dirt off the spade. If anyone moves them or vibration shifts them slightly, the connection is gone. Then you have to clean off all the dirt and oxidation to make a new connection. I hate them.

    Bill

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    Yeah... that is under the "not disturbed" clause.

    I should have added that they are never as good the SECOND time you push them on.... even if you do it perfectly.

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    With quality connectors and the approved tooling, and a use case that requires little service, there a beautiful thing.

    For high current, severe duty, corrosive environment using cheap PVC knockoff connectors with generic tooling, there about the worst you could pick. Especially on things that will require service in its life.

    The ones in the photo a a prime example. Cheap PVC connectors, generic dimple tooling, and a tough environmental application. They have been replaced / augmented once already.

    I have a surplus supply of high quality, temperd, F crimp style silver plated connectors with the proper $400 crimper. And I would not be using them in this application.

    There great for control applications and low heat and current, but in this application not a preferred choice.

    The OEM even commented to that effect in his response to the OP.

    On a 10HP or less intermittent use RPC, I could see it, but a 75HP unit built for agricultural use out in the field, I see it as a poor choice. Your mileage may vary.

    SAF

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    Quote Originally Posted by Monarchist View Post
    Trimming, once again, to any new content of value...


    Yes, actually, it is.

    Ryan is a 'country boy'. He has succeeded at far tougher challenges than this one. I took the time to check.

    He will sort this one also.

    And/or get similarly capable local help to make damned sure of it.
    You stalkin me LOL.

    I have a local friend that is a retired electrical engineer and he is on the case for me. I have sent him links to this thread and hopefully we can come up with a plan. Without even telling him the info from what you guys have said, this morning he came and looked at it and came up with it not working because it will have to be in-phase which is a crap shoot and he didn't know of any way of being able to detect it bein in-phase when we throw the power to it. It is also producing 240 out of all 3 lines while just on the Pony motor. Issue or not I dont know but I thought is was supposed to only produce on the T3 line.

    Will see what he comes up with after researching it and will give it a go. Failure is not an option.

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    Hey.... HOW the dickens is it producing 240 with no input? Something is not right here.

    Can you describe the setup better? There should not be any 240 coming out until the breaker is thrown to apply input to the idler.

    JUST ONE WAY I SEE FOR THAT TO HAPPEN........

    There could be a small voltage generated due to residual magnetism in the core. If that is the case, then it IS possible for the capacitive loading to actually "pump up" that voltage and excite the motor as a generator. If that is going on, then there MIGHT be a phasing issue....... And it WILL be a crapshoot what the phase is. (that technique of making a generator is done for some types of remote area generation)

    The reason why is because in THAT case, there IS an EXISTING current in the windings and rotor due to the capacitance supplying exciting current. So THAT has a phase, it has ALREADY "written" a pole set onto the rotor. If you start from a legitimate no-power state, there is NO such pre-existing pole on the rotor, and NO issue of phasing.

    If that is going on, it is about the first time I have heard of it happening. But it would be from the big start cap bank.

    My suggestion....

    FIRST step.... DISCONNECT ALL the capacitors, and see what goes on. It will still generate on the third wire as an RPC, but the amount of capacitance needed to work with a pony start may be different from that needed as a start capacitor. AND there will be no issue of pre-existing poles and generator action if there are no capacitors.

    You can figure out the needed capacitance for good voltage regulation after you get it to run as a "basic" RPC. And see if any generator action is occurring then. My suspicion is that the residual magnetism is due to the breaker opening transients, and the problem may go away entirely after it is made to work right (if that is possible).

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    Quote Originally Posted by beansdiesel View Post
    You stalkin me LOL.
    Almost. Was tempted to throw test gear into the boot of the Jaguar, take a spring burst-out nostalgia drive through my native Appalachia, and fall into your place to help sort this.. but .. other work intrudes..
    I have a local friend that is a retired electrical engineer and he is on the case for me. I have sent him links to this thread and hopefully we can come up with a plan. Without even telling him the info from what you guys have said, this morning he came and looked at it and came up with it not working because it will have to be in-phase which is a crap shoot and he didn't know of any way of being able to detect it bein in-phase when we throw the power to it. It is also producing 240 out of all 3 lines while just on the Pony motor. Issue or not I dont know but I thought is was supposed to only produce on the T3 line.

    Will see what he comes up with after researching it and will give it a go. Failure is not an option.
    The only surprise is him not being aware of how to 'see' where it is phasing w/r the line, as that part is dirt-simple. We'll come back to it..

    Yes, of COURSE it produces voltage-out when ponied up. Real-world has never been otherwise.

    And no, it does not wait until it hits the 'synchronous" RPM to start doing that.

    And yes, if you put a degree-wheel and strobe onto the shaft, use a 'scope to watch pretty little sine-waves as they rise up with RPM, you would notice that Lo and BEHELD! - the Mike Foxtrots actually DO relate to the physical position of the squirrell cage bars embedded in the armature when the gobnobbbler was built at the factory. Nature of real-world 3-P motors.

    Whyso?

    Capacitors OR NOT, there is a 'remanence', AKA 'remains' or 'memory' if you will, of electromagnetism left in the iron. That's 'enough' magnetism to do the do. More is needed if you want to make a generator head out of it, but the physics will obey.

    None of this s**t matters if you are still hung off a 15 kVA pole-pig, so what we need most is an update on where that is going, or IF it is going.

    Otherwise... RPC no longer involved, no longer part of the starting challenge, 'coz you can't get 'there' from 'here' whilst 'here' is only 15 kVA. Pissing UP a rope is hard, but possible. This is not.

    Just go and match a Diesel gen set to the machine tool load.

    W/R phase match detection: Go ogle 'synchroscope'. Shows you a fancy one. No need here. Can be as simple as a light, one leg on RPC/come "attempted generator", the other on mains.

    When they are far apart, light is active on the difference in potential.
    As they approach a match, it goes dark 'coz both ends are at nearly the same potential.

    Your EE guy will remember all that. He knows it - just forgot it for this context.

    PS: Show him the pole-pig AKA transformer. If even he sorts a clever way to get this Mike-Foxtrot of an oversized RPC online? It won't leave much ON the line.

    From the photo on your website, you will need a smaller gen set anyway, just to keep lights on and shop fridge running in your building even if you run only at night of a Sunday. Heat and Air-con optional..




    PPS: That is EXACTLY what Dad had to do, NACA Langley Field, VA early 1930's. Run War-Reparation German Diesels, multiple, air-started, belt-ganged, and manually synced.

    Entire Hampton area did not yet have anywhere near enough commercial power on their grid to run the fans of NACA's first full-scale wind-tunnel.
    Last edited by Monarchist; 04-25-2017 at 09:59 AM.

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    Put together a light and could see the pulses and they were waaay to fast to ever hit it. So I matched up the pulley sizes and messed around with the speed it was going on the pony until I had it nice steady pulse, timed it up, flipped the breaker and boom, the RPC was on. (took me a couple times) Will be tough to hit it consistently so Ed is looking at putting together motor starter with some kind of automatic switch that will only switch it on when the phases match. See if we can make this whole thing work much easier. Retired EE's are handy to have around...

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    Quote Originally Posted by beansdiesel View Post
    Retired EE's are handy to have around...
    LOL! "Country boys" who know whom to ask and what about don't do so bad, either..

    Don't tell him that random imprinting of phases means the damned RPC and lights are LYING to yah!



    Page two:

    Next is to find out if you can haul the load of the target machine this was all about and still have enough power left-over to keep the room lights on.

    I cannot see the average utility being exactly overjoyed about the distortion an RPC that size puts back onto their lines. Even so, if it is at all 'close to working', your EE can help motivate them as to upgrading that 15 kVA.

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    Something to consider,

    I came across a thread in another forum that seemed informational to OP situation.
    Thought it might be informational here.


    Forum Link


    The last poster on the above linked page kinda summed up a similar situation in his own words.

    "From contributor U:
    I just went through this mess you are describing, except I'm in a rural area and do not have 3-phase available. The 60 hp rotary phase converter is working but we have gotten some alarms on our CNC router related to this. The electric company said you would always be better off to use the power company's 3-phase when available. I was on a residential meter with a 15 KVA transformer and I had to upgrade to a 100 KVA. The electric company had to change my service to a 400 amp, which puts it in a CT or demand metering charge. The way they explained it was that it averages the last three 5 minute blocks every 15 minutes, it continues to average the last 15 minutes by dropping the first 5 minute block and picking up the new 5 minute block. So it really is averaging every 5 minutes.

    I had the power company come out and try to help figure out how to beat the demand meter (I even tried to get another meter set), and the only way you can help it is to turn large motors on, and let them come up to speed before turning the next one on. My electric bill is about $900.00, and right at half of that is the demand charge. If I had 3 phase available, I would not have the big start up load with the 60 hp converter, so that would reduce the bill some.

    They also explained that the demand charge is because I do not use a consistent amount of electric. If I used a small amount or a large amount all the time, I would be a better customer for them, but when you hit them with a large load for a little bit and then it tapers off, they have to purchase that power on the spot market, which is a lot more expensive for them."

    SAF Ω

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    Quote Originally Posted by SAF View Post
    Something to consider,

    I came across a thread in another forum that seemed informational to OP situation.
    Thought it might be informational here.


    Forum Link


    The last poster on the above linked page kinda summed up a similar situation in his own words.

    "From contributor U:
    I just went through this mess you are describing, except I'm in a rural area and do not have 3-phase available. The 60 hp rotary phase converter is working but we have gotten some alarms on our CNC router related to this. The electric company said you would always be better off to use the power company's 3-phase when available. I was on a residential meter with a 15 KVA transformer and I had to upgrade to a 100 KVA. The electric company had to change my service to a 400 amp, which puts it in a CT or demand metering charge. The way they explained it was that it averages the last three 5 minute blocks every 15 minutes, it continues to average the last 15 minutes by dropping the first 5 minute block and picking up the new 5 minute block. So it really is averaging every 5 minutes.

    I had the power company come out and try to help figure out how to beat the demand meter (I even tried to get another meter set), and the only way you can help it is to turn large motors on, and let them come up to speed before turning the next one on. My electric bill is about $900.00, and right at half of that is the demand charge. If I had 3 phase available, I would not have the big start up load with the 60 hp converter, so that would reduce the bill some.

    They also explained that the demand charge is because I do not use a consistent amount of electric. If I used a small amount or a large amount all the time, I would be a better customer for them, but when you hit them with a large load for a little bit and then it tapers off, they have to purchase that power on the spot market, which is a lot more expensive for them."

    SAF Ω
    Most utilities regularly buy 'some' power at spot rates. Cheap way to delay permanent investment until they are certain it has good long-term payback.

    That said, the load described is ordinarily lost in the noise of many other countervailing loads by the time it is rolled-up even part-way back the grid's distribution hierarchy.

    Even so .. IF Beansdiesel may come to see an extra $450/$500 per month, month-on-month, for mains power, and most especially if use of the end-load ON that RPC is rather sporadic?

    Seems to me that would surely go a long way towards purchase of Diesel fuel, only as needed, plus the amortization cost of a decent used gen set, mostly idle.

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    Thermite, uh, I mean Monarchist, I would tend to agree with you, a generator may be his best, lowest cost option.

    Especially if he is in the diesel business. After looking at his maypole primary distribution setup, I would guess that his utility has a limitation of a 10HP DOL start limitation, to prevent brownouts to other customers fed from that same pole. Only way to know is to ask them.

    SAF Ω

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    I was originally wrong on the 15kw tf that I thought I had. Its a 25kw. They said they would add to it or upgrade it if I needed. My main concern at the moment is getting the RPC working then move to the next problem, hopefully none.

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    Quote Originally Posted by SAF View Post
    Thermite, uh, I mean Monarchist, I would tend to agree with you, a generator may be his best, lowest cost option.

    Especially if he is in the diesel business.
    Having operated on nought BUT diesels to supply two Corps Armies (3rd & 4th Corps Tactical Zone) plus ARVN and all allied forces (Korean, Aus, Phil, etc.) with field-generated industrial gas - Oxygen, Nitrogen, Acetylene? Diesel gen sets, and lots of them, became sort of 'in the bone' natural.

    It isn't for everyone. They have their ways and their needs.

    But check his website, and find that Ryan Bean isn't just "in the diesel business", his business includes pushing the limits and solving edge-case challenges. Sourcing, brushing-up, and running a gen set would be easier for him than for most other folks.


    After looking at his maypole primary distribution setup, I would guess that his utility has a limitation of a 10HP DOL start limitation, to prevent brownouts to other customers fed from that same pole. Only way to know is to ask them.

    SAF Ω
    I'd surmise it goes beyond 'same pole', as I don't know that they have any other entity ON the same pole but his facility. That semi-twinned 2 X 200 A, one pole-pig, "400A service-shaped kludge" is a strong hint.

    Even at 25 kVA, not 15 kVA, the raw figure is but a tad over 100A, sustained @ 240 VAC, not even close to 400A. Peak inrush? Much higher, but even so, a closer match to 25 HP drama-free starting than 75 HP.

    One-step above that is where I'd expect the bottleneck to be. That is far costlier to upgrade.

    I'd go a step further and guess they might even be hoping he'd fail and give up the idea so they did not have to deal with any further upgrade at all.

    Three-phase utility power is not as cheap as RPC - until - demand metered tariffs are applied to even the 1-P, after which it isn't so bad net-net, after all, does work better, and with less need of odd interventions.

    Moving the high-load machine to some other building where 3-P is directly available - especially if that could be a shared cost / joint venture or partial sub-let, and NOT altering the present facility's utility service at all, might have better year-on-year economics than RPC or Diesel, either one.

    JM2CW, but bean-counter hat on now, (no pun intended..) sometimes the best way to tackle a problem is to not go into it at all. Might be better to find a way to go around it altogether by some more cost-efficient route.

    Whatever that new machine is meant to do, it needs power PLUS the fully-burdened wages of an operator, and a ration for maintenance and consumables. The work can almost certainly be subcontracted out, all costs already in the 'package'.

    The economics of that should be compared as well.
    Last edited by Monarchist; 04-26-2017 at 05:40 PM.

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    I have no doubt that we could get it sorted out in an afternoon in person. But, I would have meters, and other goodies, and not need to do as much guessing. Ditto for a few others here....

    BUT... An induction motor with no power applied will NOT produce any appreciable voltage out..... Load or no freaking load...... UNLESS it is set up with capacitors to provide excitation. That works, and works pretty well. I have demonstrated it here, and it is done in remote areas. There is some info from Sandia labs or similar on figuring out what is needed to optimize it, but what we need here is to NOT have it happen at all.

    It is about the ONLY way you can get 240 out of your induction motor unless you have it connected on power. AND it VERY neatly explains why your 3 HP pony cannot spin the motor.... if there is generated VA due to the capacitors, as there will be if it is doing the induction generator thing, THAT IS A LOAD. AN EXTRA LOAD, from the losses that are associated with the current flow.

    So.... You have a big lot of capacitors hooked up that are basically for starting. You are not USING them for starting.

    Get those damn things disconnected, and THEN let's see if you can get it to go.

    ALSO... DATA THAT IS NEEDED BUT WE DO NOT HAVE IT.... What does the power line sag to when you try to start the RPC? We need a "normal" and a "while being started" reading. Preferably one reading when the pony is trying to spin up the RPC, and another when the RPC is switched "on".

    IF disconnecting the capacitors does not at least let you spin it up, and there is no obvious pulley ratio issue, then yes, you may just not have enough incoming power/amperage to do what you want to do. If you cannot upgrade, the diesel genset may be your only choice.

    But, no harm in giving it another try without the capacitive "load" and generator action.

    Your 25 kVA pole transformer is a little more realistic than 15kVA, but not too much, as noted above in a prior post. It would probably let you have somewhere around 15 to 20+ HP after your other (unknown) loads are subtracted, based on getting 1 HP per 1 kVA.

    You could do better if the power factor of your big loads were corrected.

    BTW, since the PF capacitors on your idler were "stolen" to use as more starting capacitors, you DO NOT HAVE power factor correction on the input, and the idle current of that big idler will be considerably higher than the spec the RPC company provides. That is not helping you out either.

    If you DO use capacitors to correct the power factor, the way the powerco does, you can get substantially more "power" from a limited capacity line. I believe the makers of the RPC are relying on that when they spec 13A idle. Since you do not HAVE them, your idle current may be several times more.
    Last edited by JST; 04-27-2017 at 11:40 PM. Reason: deleted not on point content


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