I am trying to increase the amp reading on a motor that is drawing only.6 amps with the load on my amp meter. The reason being is that i am using a electronic overcurrent relay that has a 1amp minumium setting and at .6amps the motor won''t register on the relay. Any ideas on how to increase the current reading to fool relay into thinking it has more of a load. Using a ct built on the relay. motor 480volts 3/4 hp 1.1amp. Thanks for any input.
motor load
- Thread starter hawkeye23
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You haven't told us anything about how the relay interfaces with the motor to measure amperes.
Ity may be to small but it is not uncommon for larger relays to use window CTs, that is the wire feeding the motor is run through the CT. The amps that the relay sees can be doubled by simply running the conductor back around and through the CT a second time. Other than that I can't see how you can fool the relay into reading a higher ampere.
Ity may be to small but it is not uncommon for larger relays to use window CTs, that is the wire feeding the motor is run through the CT. The amps that the relay sees can be doubled by simply running the conductor back around and through the CT a second time. Other than that I can't see how you can fool the relay into reading a higher ampere.
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
Yep, that's how to do it. If you don't have a window type CT on your EOCR, you have the wrong EOCR.
Most likely because of the ampacity described it probably does not employ a window CT.
More often that not the OP provides just barely enough information to seed the question and the rest of use are left to guess what it is.
If he were to have described what he had instead of using a generality this probably would have been answered in one reply.
The relay has a ct , it uses a jumper to change or increase the range of the ct. As stated in first post the lowest current range is 1amp. [ 1amp to 6amp.] if a higher range is needed a jumper is moved that is built on to relay.
My intention was to find a way to have this relay read the current draw of the motor , but as you have stated i used the wrong relay.
Thanks for the help , will replace relay with correct size.
My intention was to find a way to have this relay read the current draw of the motor , but as you have stated i used the wrong relay.
Thanks for the help , will replace relay with correct size.
- Location
- Massachusetts
Hawkeye what they are saying is if you run the motor lead through the CT twice it will read it.
It is important that you wrap it around once in the correct direction which would effectively double the current that the CT senses. If you wrap it around backwards it will cut the current that the CT senses by half which is what you don't want to do.
But, it you do it backwards no harm is done just unwrap it and wrap it through the other direction. Generally take the lead that goes to the motor and bring it up, around and through the CT again and that should do it.
- Location
- Illinois
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- retired electrician
I don't know how you can wrap it backwards. As long as both passes of the conductor are wrapped in the same direction, you will effectively double the current. If you somehow make one wrap in one direction and the second one in the opposite direction, they will cancel and see very close to zero current.
I was going from memory from an application publication that I may still have somewhere.
Now you have caused me to rethink my statement and I'm going to have to see if I stall have it around.
Fantastic!! You have to love it whaen a plan comes together with an eay solution.
Just to confirm that tou ran the conductor through the window and then around the CT once and back through the window again.
I just want to clarify your reference to 'wrapping it around twice.'
Just to confirm that tou ran the conductor through the window and then around the CT once and back through the window again.
I just want to clarify your reference to 'wrapping it around twice.'
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
The "wrapping backward" thing you remember is likely the old practice of "fine tuning" a CT output by wrapping the SECONDARY conductors back through the window. Wrapping them one direction added current to the secondary in smaller percentages of the primary current, wrapping them the other direction subtracted. So for example if you had a 500:5 CT and you wanted a 200:5 ratio, passing the primary through once more got you to 250:5, then you would wrap the 5A side through 10 times in one direction to take off another 50A (250:5 = 5:1, x 10 = 50). If you wanted 300:5 instead, you would wrap the secondary 10 times in the other direction. I'm going strictly by memory here, I may be wrong on the ratios, but I'm just explaining the concept. It's been so long since I've had to do that, I'd look it up again before attempting it.
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You know, that seems to ring a bell. My curiosity has been peeked and I?m going to have to look through my achieves for the old application bulletin. If I happen to find it I'll scan and post it.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Thanks,
Bingo!! Ah ha, it was the secondary where how you wound the secondary through the wind that mattered.
You saved me from digging through my archives that I have been slowly throwing away. I try to ut it in 1/2 once a year.
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
One day as a "gift", my wife and daughter cleaned out the "clutter" (as they saw it) in my man cave. A lot of that was my archive of stuff that I intended to scan and digitize some day before recycling the paper. All lost now... :rant:
But I have to say, with good Google skills, I haven't missed it. Much...
One day as a "gift", my wife and daughter cleaned out the "clutter" (as they saw it) in my man cave. A lot of that was my archive of stuff that I intended to scan and digitize some day before recycling the paper. All lost now... :rant:
But I have to say, with good Google skills, I haven't missed it. Much...
Yes, it takes time to scan the documents and then file so that you can find them.
Your wife and daughter may have done you a big favor.
Remember when you had that film camera and you were very judicious in what you took photos of and haw many you took? Then the digital camera came along and now its mega pictures that can be stores on your HD of and a 10cent CD. And how many do you really need or will be looking at again but yet are afraid to delete them.
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