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Size And Type Of 3 Phase Transformer?
- Thread starter Ropata
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- Sep 25, 2014
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I suppose that depends on what you are planning to do? If you are putting a transformer between an RPC and a machine, I would suggest a transformer at about 2x the largest motor you intend to run. For example if you are going to power a 5 HP motor, that is about 4kW. So go for a transformer rated to at least 8kVa.
What type?? Nothing special here - assuming you are looking at a straight forward 3 phase transformer?? You probably want one of those small, dry type, air cooled boxes (sits in the corner and humms).
What type?? Nothing special here - assuming you are looking at a straight forward 3 phase transformer?? You probably want one of those small, dry type, air cooled boxes (sits in the corner and humms).
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- May 24, 2016
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- Joined
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I've tried looking everywhere for this type of dry transformer to these specs but am confused as hell. Am I after a 7.5kw or 7.5kva?http://www.kayind.com/sites/default/files/pdf_library/Step_up_connection_diagram.pdf
This what I'm trying to achieve, I have all but the transformer. Is there a site that specialises in these transformers?
This what I'm trying to achieve, I have all but the transformer. Is there a site that specialises in these transformers?
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- Dec 8, 2013
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You want kva.
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- Feb 8, 2014
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Normally transformers are rated in KVA. In most cases, when sizing transformers, you can use KVA and KW interchangeably. So yes, a 7.5 KVA transformer would work for a 10 HP motor, but it looks like you are only going to be running about 2.5 KW. I assume the 10HP is for the RPC.
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My little Maho mill has a 2 speed motor (575V). On the high speed setting, it is rated at 2.2kW. I am running it on a 5HP RPC and with a 6KVA transformer. It does not like starting on the high speed setting (I don't know if it is a transformer issue or something to do with the RPC). The mill has a 9 speed gear box, and I normally operate on the low motor speed (an adequate selection for most of what I do). Occasionally I use the high speed, by first pressing the low speed, then push high speed (each has its' own contactor) - works fine.
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The transformer in the the RPC drawing is an isolation transformer. I'm not sure if an auto transformer would work with a RPC, I'd have to think about that for awhile. You might check with the RPC manufacturer on that one.
Any heavy industrial facility might have something like that around, I would check with some local electricians, especially ones that do industrial. They might have some leads on a suitable transformer kicking around. I know where 3 of them are at, but I'm a long ways from you. You can always go larger on the KVA if something is available for a reasonable price.
Any heavy industrial facility might have something like that around, I would check with some local electricians, especially ones that do industrial. They might have some leads on a suitable transformer kicking around. I know where 3 of them are at, but I'm a long ways from you. You can always go larger on the KVA if something is available for a reasonable price.
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- Dec 8, 2013
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- 2,651
It work fine as long as you did not forget that your neutral on the output side would be the middle of one of the legs.