Re: [Emc-users] oversize transformer question
We picked up a free oversized transformer for our shop 3 phase and the inrush would trip the breaker so it was useless to us. John On 17 Oct 2007 at 11:17, [EMAIL PROTECTED] wrote: Mark already said that the transformers are at least twice as big has he really needs. But they are free (other than shipping), so he's asking us what gotchas there might be in using an oversize transformer. As long as there aren't any technical issues, an oversize but free part often beats a right-sized but expensive one. In this case however, I think inrush current is a significant technical issue. Regards, John Kasunich - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
Jim Coleman wrote: i was thinking the light bulb idea when i read it, i remember reading an article on a homebuilt 1000 watt audio amp, he did that because of the inrush current tripping a breaker. i was just wondering how many bulbs in parallel it would take to handle the current without blowing instantly? thinking of standard 100 watt incandescents. If you have a 120V line and 120V bulbs, you don't have to worry about them blowing. Even if the load looks like a dead short at turn on, the lights never see more than 120V. What the number of lights does change is the charge time. Each bulb provides a certain amount of current. More bulbs in parallel means more current and faster charging of the capacitors. I think a single 100W lamp would be fine for the power levels we're talking about. Regards, John Kasunich - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
It should be possible to use a slightly higher current breaker or one with longer time delay for magnetic devices? Failing that a knife switch with time delay fuses should handle the job. Rayh On Thu, 18 Oct 2007 06:06:15 -0500, Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net said: We picked up a free oversized transformer for our shop 3 phase and the inrush would trip the breaker so it was useless to us. John On 17 Oct 2007 at 11:17, [EMAIL PROTECTED] wrote: Mark already said that the transformers are at least twice as big has he really needs. But they are free (other than shipping), so he's asking us what gotchas there might be in using an oversize transformer. As long as there aren't any technical issues, an oversize but free part often beats a right-sized but expensive one. In this case however, I think inrush current is a significant technical issue. Regards, John Kasunich - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
John Thornton wrote: We picked up a free oversized transformer for our shop 3 phase and the inrush would trip the breaker so it was useless to us. You could probably put light bulbs or reistors in series to magnetize the transformer core in sync with the line, then shunt the resistance out. (Of course, this would not be a standard, off the shelf NEMA setup.) Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
6.67kva 120v primary, 120v secondary I'd prefer 240v primary, but the nice thing about this one is that it's cheap (aside from the shipping). I don't yet have the weight, I am guessing from the weight of similarly-rated transformers. He's got three, and he said they are free for pickup - but California is a little far away to drive :) 130 miles E of San Diego, if anyone nearby is interested - I can put you in contact. Mark --- Jon Elson [EMAIL PROTECTED] wrote: Mark Pictor wrote: What are the drawbacks of an oversized transformer? Bulky, not as efficient, ??? The one I am looking at is a little over 2 times the size I guesstimated that I need. At $100+ for shipping, I'm not sure if it's worth it or not. It would allow future expansion, but would probably still be overkill. There are lots of transformers out there. I sure wouldn't pay $100 shipping for a transformer except in very special cases! There HAS to be a better deal somewhere, unless this is a 5+ KVA transformer, or you need it FedEx'ed next day. Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
With the price of copper these days... I assume from shipping that this is copper and probably potted. Is this intended for isolation or what? Rayh On Wed, 17 Oct 2007 01:00:28 -0700 (PDT), Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net said: 6.67kva 120v primary, 120v secondary I'd prefer 240v primary, but the nice thing about this one is that it's cheap (aside from the shipping). I don't yet have the weight, I am guessing from the weight of similarly-rated transformers. He's got three, and he said they are free for pickup - but California is a little far away to drive :) 130 miles E of San Diego, if anyone nearby is interested - I can put you in contact. Mark --- Jon Elson [EMAIL PROTECTED] wrote: Mark Pictor wrote: What are the drawbacks of an oversized transformer? Bulky, not as efficient, ??? The one I am looking at is a little over 2 times the size I guesstimated that I need. At $100+ for shipping, I'm not sure if it's worth it or not. It would allow future expansion, but would probably still be overkill. There are lots of transformers out there. I sure wouldn't pay $100 shipping for a transformer except in very special cases! There HAS to be a better deal somewhere, unless this is a 5+ KVA transformer, or you need it FedEx'ed next day. Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
Mark Pictor wrote: 6.67kva 120v primary, 120v secondary I'd prefer 240v primary, but the nice thing about this one is that it's cheap (aside from the shipping). I don't yet have the weight, I am guessing from the weight of similarly-rated transformers. 6.67kVA at 120V is 55 amps. The inrush current is going to be fierce, probably 200-500A for the first couple of cycles. I agree that a 240V primary would be better. If I only needed a couple kVA, I would look for something that is a better fit to the application. Regards, John Kasunich - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
Mark Pictor wrote: 6.67kva 120v primary, 120v secondary I'd prefer 240v primary, but the nice thing about this one is that it's cheap (aside from the shipping). I don't yet have the weight, I am guessing from the weight of similarly-rated transformers. What the HE** do you need a 6.67 KVA transformer for? This can't be for a servo motor power supply unless you have a 50 foot KearneyTrecker bed mill. You should be able to find step down transformers at the local scrap yard. You'll have to pay scrap price for them, which is going up lately. These usually can be set for 220 or 440 in, and 120 or 240 out. Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
Jon Elson wrote: Mark Pictor wrote: 6.67kva 120v primary, 120v secondary What the HE** do you need a 6.67 KVA transformer for? Mark already said that the transformers are at least twice as big has he really needs. But they are free (other than shipping), so he's asking us what gotchas there might be in using an oversize transformer. As long as there aren't any technical issues, an oversize but free part often beats a right-sized but expensive one. In this case however, I think inrush current is a significant technical issue. Regards, John Kasunich - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
I knew there would be inrush current to the capacitors, but I didn't realize that the transformer, in and of itself, would have an inrush current. Guess that shows how much I know! I was planning to use one or more motor run capacitors to limit inrush current - use a relay in parallel with the cap, and close the relay a few seconds after applying power. Now that Jon brought it up, I think I will visit the local junkyard instead. Mark --- John Kasunich [EMAIL PROTECTED] wrote: Jon Elson wrote: Mark Pictor wrote: 6.67kva 120v primary, 120v secondary What the HE** do you need a 6.67 KVA transformer for? Mark already said that the transformers are at least twice as big has he really needs. But they are free (other than shipping), so he's asking us what gotchas there might be in using an oversize transformer. As long as there aren't any technical issues, an oversize but free part often beats a right-sized but expensive one. In this case however, I think inrush current is a significant technical issue. Regards, John Kasunich - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
I don't have my figures, but I remember looking for a 3kva isolation transformer before. This is a little more than twice that size, as I mentioned in the OP. Now that I think about it, my 3kva figure was probably conservative. I hadn't thought of the scrap yard. That would probably be a lot cheaper. Mark --- Jon Elson [EMAIL PROTECTED] wrote: What the HE** do you need a 6.67 KVA transformer for? This can't be for a servo motor power supply unless you have a 50 foot KearneyTrecker bed mill. You should be able to find step down transformers at the local scrap yard. You'll have to pay scrap price for them, which is going up lately. These usually can be set for 220 or 440 in, and 120 or 240 out. Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
At 01:17 PM 10/17/2007, you wrote: I knew there would be inrush current to the capacitors, but I didn't realize that the transformer, in and of itself, would have an inrush current. Guess that shows how much I know! I was planning to use one or more motor run capacitors to limit inrush current - use a relay in parallel with the cap, and close the relay a few seconds after applying power. Now that Jon brought it up, I think I will visit the local junkyard instead. Mark --- John Kasunich [EMAIL PROTECTED] wrote: Jon Elson wrote: Mark Pictor wrote: 6.67kva 120v primary, 120v secondary What the HE** do you need a 6.67 KVA transformer for? Mark already said that the transformers are at least twice as big has he really needs. But they are free (other than shipping), so he's asking us what gotchas there might be in using an oversize transformer. As long as there aren't any technical issues, an oversize but free part often beats a right-sized but expensive one. In this case however, I think inrush current is a significant technical issue. Regards, John Kasunich Put a light bulb in series with the primary. Flip the switch and the bulb flashes and gets dim as things charge up, then flip a second switch to short out the light bulb. __ Andre' B. Clear Lake, Wi. - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
Mark Pictor wrote: I knew there would be inrush current to the capacitors, but I didn't realize that the transformer, in and of itself, would have an inrush current. Guess that shows how much I know! Yup. It varies with the transformer design, and if you end up using a 240 V primary winding on 120 V, the inrush will be very small. What is going on is that the transformer integrates volts times time, and the iron in the core is designed to just handle the rated conditions, where the magnetic field builds in one half cycle, and is cancelled out in the next half-cycle. But, when you close the switch, the power line phase at that moment could be anything. If it happens to be right at the voltage zero crossing, then it gets a complete half cycle of the same polarity starting from zero magnetic field, and that saturates the core. The transformer will make a huge buzz for a half second, and the current will be enormous. I was planning to use one or more motor run capacitors to limit inrush current - use a relay in parallel with the cap, and close the relay a few seconds after applying power. This will kill your relay. Shorting a capacitor bank charged to 168 V peak will cause a minor explosion, and the L-C circuit will never settle. You need to use a low-value resistor, not capacitor, for this purpose. Now that Jon brought it up, I think I will visit the local junkyard instead. Depends entirely on the junkyard, of course, but almost any instance where old machinery is torn out of a plant, they get these transformers. Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
i was thinking the light bulb idea when i read it, i remember reading an article on a homebuilt 1000 watt audio amp, he did that because of the inrush current tripping a breaker. i was just wondering how many bulbs in parallel it would take to handle the current without blowing instantly? thinking of standard 100 watt incandescents. off topic, i bet that would look like a scene from an old horror movie when he turns it on haha. - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] oversize transformer question
What are the drawbacks of an oversized transformer? Bulky, not as efficient, ??? The one I am looking at is a little over 2 times the size I guesstimated that I need. At $100+ for shipping, I'm not sure if it's worth it or not. It would allow future expansion, but would probably still be overkill. Thanks Mark - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] oversize transformer question
Mark Pictor wrote: What are the drawbacks of an oversized transformer? Bulky, not as efficient, ??? The one I am looking at is a little over 2 times the size I guesstimated that I need. At $100+ for shipping, I'm not sure if it's worth it or not. It would allow future expansion, but would probably still be overkill. There are lots of transformers out there. I sure wouldn't pay $100 shipping for a transformer except in very special cases! There HAS to be a better deal somewhere, unless this is a 5+ KVA transformer, or you need it FedEx'ed next day. Jon - This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now http://get.splunk.com/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
