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Thread: MEP-002A and -003A main breaker

  1. #11
    Blind squirrel rehabiltator Speddmon's Avatar
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    Ike,

    You are absolutely correct but you forgot to mention that a lot, if not all, newer AC compressors are using scroll compressors. Which by their very design start under almost no load.

    To everybody else, I just hung up the phone with an engineer at Heinemann about the breaker problems. Here is some background.

    First off, the breakers are a relay trip breaker as well as magnetic trip. What this means is that the R3 adjustment is pretty critical to the operation of the breaker. The main contacts act as a switch only, and the main 100A rating of the breaker basically means nothing more than that is the switching capacity of the main contacts. The actual trip rating of the breaker comes from the relay inside and that rating is 825mA (0.825 amps).

    Now, when you have a large inductive spike such as your heavy motor loads being discussed here. That's when the magnetic trip comes into play. There is a plunger inside the trip relay inside the breaker. If the spike if large enough, it will trip the breaker before the relay even has a chance to. The engineer told me that by increasing the resistance of the variable resistor (R3) you can increase the delay of the magnetic trip also, but then you could be running the breaker out of the specified range for an over current situation (which is where the relay trip comes into play).

    So in conclusion, and I said earlier, go through and properly adjust the R3 resistor and see if that doesn't help out your motor starting capacity. And if you still desire a bit more, you can AT YOUR OWN RISK increase the resistance of R3 some and see if that helps. It is a very good possibility that the R3 resistor is bad or going bad. They are nothing more than a small cheap potentiometer, and we replace them all the time here in the steel mill because they go bad quite often on our equipment. They are probably the cheapest thing on the equipment in price and quality both.
    Quote Originally Posted by Recovry4x4 View Post
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    MEP-002a & MEP-003a Spin-on oil filter kits are still 4 sale in the classified section

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    Speddmon, don't get me started on scroll compressors, they may be to the point of being ok for air conditioners now (and even getting common, I have not looked at how common in the last year or two), but they have a long way to go on the refrigeration end of the business that I regularly have to deal with. (scroll compressors are a lot cheaper than traditional semi-hermetics, but for now have a much shorter life expectancy). Having said that I think they will be the future for many applications.

    Ike

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    Quote Originally Posted by Speddmon View Post
    Ike,

    To everybody else, I just hung up the phone with an engineer at Heinemann about the breaker problems.
    Thanks for the effort!
    I had planned on taking some time this weekend studying the schematic to try to figure this out on my own...

    I'll take 1 of my -002's and one of my -003's and check the R-3 setting, adjust if necessary, and see if any of them are out of spec.

    If this doesn't solve my starting surge issue, I'll make the necessary adjustments with R3 to make it work.

    I'll be sure to post my findings here...

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    Speddmon, I am going to dive into this on Saturday morning and get some data on how R3 affects trip delay and setpoint, but I just wanted to make sure I fully understand how this breaker works before I start making adjustments. So, I just wanted to try to clarify a few things:

    1. The magnetic trip is a function of how much current is flowing through the main contacts; a large enough current spike essentially overpowers the holding force of the relay, causing it to trip the breaker. Is this correct?

    2. The relay trip is a function of how much current is flowing through the smaller lugs in the field/control circuitry; when it exceeds the breaker's setpoint, it actuates the relay, causing the breaker to trip. Is this also correct?

    3. If 1 and 2 are both correct, it would seem to me that adjusting R3 for a greater current flow through the breaker would actually increase the holding power of the relay (making it more resistant to surge trips), but decrease the relay's effective trip setpoint (making the relay trip earlier under steady state loads). This is the effect that I am trying to achieve...do you agree with this assessment?

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    Not quite, The relay trip is a function of how much current is flowing through the coil of the relay and nothing more. The main contacts of the breaker act as switching contacts ONLY.

    If you look at the schematics for the 003a you'll see that the current going through R3 is produced by a current transformer (CT) located in the CT/CVT assembly. The CT puts out current directly proportional to the current in the main line, only reduced due to the transformer action taking place in the CT. As you place more load on the generator, the current produced by the CT increases as well. That's why you are to run the set in 120 volt mode at rated load and adjust R3 until you see .75 amps on your meter. I don't know what the turns ration of the CT is but obviously .75 amps equates to about 104 amps on the main line since that's the rated load of the generator.

    When the current across R3 is set to .75 amps, and the breaker doesn't trip until that current reaches .825 amps, you basically have a 110% capability much like fuses and normal breakers. Meaning the breaker will not trip under normal loading until you are at 110% of the rated load...or 110% of 104 amps...114.4 amps. You can make the breaker trip sooner too, if you are only running the generator at 50% load and you adjust R3 to get .75 amps, then you are basically setting the trip setting of the breaker at 110% of 52 amps or...57.2 amps. That's why it is critical to have the R3 adjustment done properly, because if you set R3 too low...lets say .4125 amps (1/2 of .825 for simplicity sake) when you are running the set at rated load, then you are basically setting the breaker to trip at 200% of the rated load...or 208 amps...THAT"S BAD!!!!!!

    Back to the operation of the breaker. I kind of summed up what happens and how the breaker works during normal loading and operation. When you start a heavy inductive load, such as your large compressor, that's where the magnetic (actually Hydraulic-Magnetic) trip comes into play. When you start a large inductive load, there is a large magnetic field produced called Magnetic Flux. When you start the motor, flux is induced into the relay coil and starts to move the plunger. If the surge is not too great, the flux will very soon dissipate and the current produced in the CT will start to act on the relay coil and the breaker will act normally and not trip. If the flux is very large, the plunger will move far enough on it's own to trip the breaker. This action basically acts as a time delay that is proportional to the overload setting...the higher the surge the faster the breaker trips. So if your R3 setting is set too low like given in the 50% example above, the surge that it takes to trip the breaker instantaneously will be decreased as well.

    Attached is a snippet of a document made by Eaton (Heinemann) explaining the process somewhat.

    I hope I didn't confuse you too much, but it is pretty important to have that R3 set to the proper value. If you want to bump up you capacity just a little, it's not going to take much at all to do it.
    Attached Files Attached Files
    Quote Originally Posted by Recovry4x4 View Post
    That's why I knew the answer and you didn't. I read the kindling.
    He is "anti-doghead".

    Even a blind squirrel finds an acorn every now and then!



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    1985 M1028/M1031 w/700R4 "Road Oiler"
    MEP-003a 3000 hrs
    MEP-003a 1500 hrs
    1964 Case 530CK "Construction King" Backhoe/loader "Yard Oiler"

    MEP-002a & MEP-003a Spin-on oil filter kits are still 4 sale in the classified section

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    Quote Originally Posted by Speddmon View Post
    I hope I didn't confuse you too much
    Not at all! I'm an ex-Navy Nuclear Electronics Technician; I have a good solid understanding of electronics.
    I appreciate the help and the time you took to ask the engineer at Heinemann about this issue. I was going to try to figure most of this out on my own...you've probably saved at least a few hours of my weekend.
    I'll spend some time with one of my -002's on Saturday and let you know what I learn...

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    Speddmon I want to publically thank you for taking the time to explain things so us dummies out there can understand. In fact, I was having problems with one of my 003a's and i read old posts that you did that helped me troubleshoot the problem. The TM is good, but you are great. Once again sir, thank you for taking the time, to break down the items you do that helps all of us non-electricians on this site. We are lucky to have you here as a member.

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    Blind squirrel rehabiltator Speddmon's Avatar
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    Quote Originally Posted by Recovry4x4 View Post
    That's why I knew the answer and you didn't. I read the kindling.
    He is "anti-doghead".

    Even a blind squirrel finds an acorn every now and then!



    1970 M35A2 "The Stone Wagon" SOLD
    1985 M1028/M1031 w/700R4 "Road Oiler"
    MEP-003a 3000 hrs
    MEP-003a 1500 hrs
    1964 Case 530CK "Construction King" Backhoe/loader "Yard Oiler"

    MEP-002a & MEP-003a Spin-on oil filter kits are still 4 sale in the classified section

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    Sewerzuk,

    Have you had a chance to play around with your generators yet? I am curious to know if the R3 was out of adjustment, and if so, did adjusting it fix your problems???????
    Quote Originally Posted by Recovry4x4 View Post
    That's why I knew the answer and you didn't. I read the kindling.
    He is "anti-doghead".

    Even a blind squirrel finds an acorn every now and then!



    1970 M35A2 "The Stone Wagon" SOLD
    1985 M1028/M1031 w/700R4 "Road Oiler"
    MEP-003a 3000 hrs
    MEP-003a 1500 hrs
    1964 Case 530CK "Construction King" Backhoe/loader "Yard Oiler"

    MEP-002a & MEP-003a Spin-on oil filter kits are still 4 sale in the classified section

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    General sewerzuk's Avatar
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    Quote Originally Posted by Speddmon View Post
    Sewerzuk,

    Have you had a chance to play around with your generators yet? I am curious to know if the R3 was out of adjustment, and if so, did adjusting it fix your problems???????
    I decided to wait until I could get my hands on a good clamp ammeter; I wanted as much info as I could get before I started playing with R3.

    I just picked up a used Fluke 337 off of Ebay; got it in the mail a few days ago. It has the ability mt record min, max, and peak inrush currents. I'm going to hit my 003's and 002's with some starting surges and find out exactly what current is causing them to trip, then I'll begin toying with the R3 setting...

    I'll be sure to post my findings here.

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