OK. Is the mains voltage precise anywhere in the world? The US specification is +/- 5% (228V to 152V), at the source (i.e. at the transformer). Losses in the wiring will put it on the low side of those numbers.
********** No it?s not and arguing about whether its 220V or 240 is just arguing because you want to argue when in most places it is actually neither.
Different kettle of apples. That's not "204V" and rarely, if ever, found in residences.
********** Just being thorough since you choose to pick at nits. LOL.
Sure, you have an load imbalance. Not surprising but hardly relevant.
*********** Relevant? Sure it is. Its nt 240V. LOL. 2 volts is hardly a significant imbalance though. It?s the same at the lugs with the main breaker off. So... if anything the "neighborhood" has an imbalance. LOL.
OK. But here we are.
************ Yeah, but any electrician will recognize that arguing over whether its 220 or 240 is pointless. An engineer might note that you can carry more net power at 235 than at 220. Again. LOL.
Agreed. 20A single phase should be good for 5HP but I prefer a bit more overkill also. I usually do a home-run from the tools back to the panel, unless I know that two outlets can never be used at the same time. ...and with 240V circuits, usually then, too.
************* I think we mainly agree and are just quibbling over minutiae. One also needs to recognize that bogging down the motor at the tool may have a net current draw that is higher than its nominal or even rated current draw unless loading it up until it bogged down was how the motor was rated to begin with. Then its really not a 3HP motor. Not 3 useable HP anyway. Also start up of the that 5HP (or larger) rotary may draw more than its nominal rating at peak load as well. In rush of the caps can be quite high and initial inertial load can be higher than expected. The odds are 20 amps at the range from 220 to 245 (there you happy now LOL) is adequate for the job anyway. Especially since breakers do not trip instantly at peak rating.
wrote in message news: snipped-for-privacy@4ax.com...
On Tue, 19 Jun 2018 10:39:35 -0700, "Bob La Londe" wrote:
NO, I'm pointing out that the tolerance is 5% and hardly matters in this discussion.
But it has nothing to do with the discussion.
That's what I said. It's not relevant.
No, it's probably in your house.
But the issue is a 3HP motor. The difference between 220V and 240V, or any tolerance of the 240V is irrelevant. A 20A circuit is good enough.
No, the point is whether 20A 240V circuit is enough for a 3HO motor. It is. Period.
************* That may be the point of the OP, but you are the one who chose to establish himself as a self appointed egotistical god of all things electrical and argue over every little thing. My very first post established with facts and numbers that conservatively a 3HP motor could be run on 220 or 230 or 240 under or whatever arbitrary number you choose to claim at under 20 amps and I noted it has a particularly large safety margin. I'm not sure why you are even arguing that point. I established it before you even let your fingers spew across your keyboard. However, You seem to pigheadedly refuse to acknowledge that there is more in the OPs circuit than just a motor. He asked specifically about a phase converter which is notoriously in efficient. Rotaries and static converters are both inefficient. Even VFDs are very inefficient when used as phase converters. It almost seems like you are against the very fact that I choose to be conservative and safe with my calculations and choosing unimportant things to argue about like whether or not the established standard of 220V or the closer to 240V actual (but almost never exactly) is correct. Its like arguing your Chevy is better than mine because yours is blue. You can go out and find new outlets for example that are labeled at different primary voltages even today.
What? That makes absolutely no sense. A 3HP motor will draw its rated current *AT* 3HP. It will be "bogging down" ("slipping phase") at that point.
************* I suppose with the number of crap motors on the market today that is true. Between cheap import motors that are literally rated by loading them down until they stop and measuring the current, and name brand motors struggling to compete with cheap imports very few electric motors today are capable of putting out their useable rated power for even a fraction of a second. That wasn't always the case. Like your petty argument about 220V vs 240V to make yourself feel superior, or whatever it is that motivates you, that wasn't always the norm. There are still motors out there that don't lie on their data plates. I have 3 phase spindle motors that I have literally run at their rated horsepower. Not for very long, but they can actually run at rated power for a short time. No I didn't run a recording meter on them (and current is actually NOT an accurate factor to measure of horsepower), but when calculating cutting loads mathematically I found corners and sharp inside turns calculated right at their rating, and the motor didn't bog down or die. Of course I value those motors very highly, and I try not to ever run them like that as it shortens their life and particularly bearing life substantially. As I have learned more about machining techniques I try to keep my motors well under their ratings. Heat buildup is the killer. However I have to acknowledge that even 35 years ago machine builders questioned the output of their motors and designed machines with a safety margin. I have a 1984 (I can never remember for sure the year) 2 ton CNC mill (light weight by today's standards) with a 5HP spindle motor and the mill builder rated the mill at
4HP. Of course they are running a 3.7Kw (5HP) VFD to control the spindle.... hmmm not quite a 30% derating, but they probably intended the machine to actually be run directly on 3 phase. I have never ever bogged that motor down at normal speeds. I do run it as low as 96RPM at 3hz where it can bog down if you don't plan well, but if you can't do that you shouldn't be running it at all. I suppose I have to add another caveat. Many motors are capable of their peak horsepower for a second or two, but often not at their standard line frequency speed. I have several 24K rpm
400hz motors that peak around 19000 (+/-) rpm. They are not as linear as people would like you to believe. I've found similar results with more conventional motors running at the 30-120hz that most 3Phase motors are capable of running. Again, just being thorough. Want a great example? Open one of those high tech modern washing machines I mentioned in my first post and read the voltage and frequency tag on the basket motor.
Hardly. The start capacitors are irrelevant.
*************** Any current draw even for a fraction of a second is relevant. Although as I stated before (so you don't have to argue an established point all over again) even IF (
I have a home made Single phase 220 to 3-phase at 380v/phase from a rotary and six transformers. Each leg has a step-up transformer and a series boost in each leg. I control the high voltage from contactors so I can have SP-220, 3-p-220 and 3p-380. I use the hv 3p on my surface grinders. Each grinder has three motors so the pain was make a 3p system HV and use smaller cable or buy larger cable and convert 6 motors.
I took the expensive route.
Once you find what you get - then you look into what is needed to fixit up. MSCdirect.com has convers both rotary and static.
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