So many posts about phase conversion to 3-phase

15a is roughly about 2hp equivalent consumption of the single phase line @230v

Mike are you sure that it's about 2HP. I would have thought it would be closer to 4HP. unless it has a very poor power factor.
 
Mike are you sure that it's about 2HP. I would have thought it would be closer to 4HP. unless it has a very poor power factor.
the draw is slightly greater than 2hp on the single phase input, a 3hp single phase motor would draw around 17a full load current
full load current for a 3 phase 10 hp motor running on 3 phase 230v, is about 28 amps
 
the draw is slightly greater than 2hp on the single phase input, a 3hp single phase motor would draw around 17a full load current
full load current for a 3 phase 10 hp motor running on 3 phase 230v, is about 28 amps

Mike, I have just realised my confusion, I'm not used to thinking in terms of 3 ph at those low voltages, here in downunder all our single ph is 240v and our 3 ph is 415 v.As a result I'm thinking of currents roughly half of what you are using. Sorry, thanks for the patience.
 
No worries mate!
We have 240v single phase and 208 or 230v 3 phase as well as 440/460v 3 phase
I have wired up a few machines that came from down under to run on our supply
The machines come in with 415v 5 wire plugs
I omit the blue neutral and i convert the control systems. the remaining 4 wires do the work with 208-230v 3 phase supply to the machine.
The conversions are battle tested and have served many well

All the best
 
That might not be energy that you're paying the power company for; there's a phase-angle correction,
which you can check. Turn off electric water heater and furnace/AC, look at five minutes of
power-company-meter reading with the RPC running, then turn it off and look at another five minutes.

Some of the current you're measuring is due to the start/run capacitors in the RPC, and doesn't
mean real electric power. The power meter indicates this, but ammeter measurements don't.

Interesting, Whitmore. I'll do that. I just figured that if my ammeter shows 15 amps, then that's what I'm paying the power company for.


OK you had me a little confused, you said 15A on one leg and 14A on another, I assumed you were referring to phase leads, so am I to assume you are referring to the single phase active and neutral leads,if so they should read the same. I still think it's rather high although Ulma doctor says it's about right. And I suspect he knows more about it than I do. It will be interesting to see how much it draws when running a good 3 phase load.

As for running the RPC outside or in any out of the way place, you could wire up a lamp that will show when the RPC is powered on. A mate of mine did that with his shop compressor, he had a green light next to the remote on off switch.

Thank you, Bobshobby. I'm using a clamp-type ammeter, clamping it around one input lead to the phase converter motor and then the other. It does seem strange that they're not reading the same current. All current going into the motor should also be going out, shouldn't it? But indeed, one leg consistently reads 14 amps while the other reads 15.
 
Interesting, Whitmore. I'll do that. I just figured that if my ammeter shows 15 amps, then that's what I'm paying the power company for.




Thank you, Bobshobby. I'm using a clamp-type ammeter, clamping it around one input lead to the phase converter motor and then the other. It does seem strange that they're not reading the same current. All current going into the motor should also be going out, shouldn't it? But indeed, one leg consistently reads 14 amps while the other reads 15.

Interesting and somewhat intriguing, I can only assume you are losing 1 Amp somewhere. Is it possible you have an earth leakage problem? Do you have earth leakage breakers on your system or not? I wonder if Ulma doctor can throw any light on this, as it is my understanding that current in equals current out.
 
No worries mate!
We have 240v single phase and 208 or 230v 3 phase as well as 440/460v 3 phase
I have wired up a few machines that came from down under to run on our supply
The machines come in with 415v 5 wire plugs
I omit the blue neutral and i convert the control systems. the remaining 4 wires do the work with 208-230v 3 phase supply to the machine.
The conversions are battle tested and have served many well

All the best

Glad you know what you are doing, electricity was not my best subject when I studied marine engineering, sure I get the basics of generation and distribution, even fault finding and repair on a known system, but when it comes to wiring up motors onto a system that is different from their name plate, I'm well out of my depth. BTW your 5 wire 3ph plug woud have been L1, L2, L3, N and E. If you leave the blue out that is the N does that mean you are usinhg the E (yellow/ green or just green on older stuff ) as your N. Are you wiring star (WYE) or Delta?

The 240v single ph here is about to change to 230v to bring us into line with Europe as they change from 220 also to 230v. We will retain the 50hz and they will keep their 60hz, So it's only a partial common system, but we will avoid the problem we have had for years where asian manufacturers design and build to the much larger European market at the old 220v and just relabel them 240v for us here in downunder, as a result we have had an unacceptably high level of failures in motors, transformers, and other induction devices Taiwan has recently and finally caught on, but the rest of asia, China in particular is still a problem.
 
Hi Bob,

Most 3-phase machinery doesn't use the neutral from what I've seen, when it does it's to get 240 for a control and low-volt lighting transformer or such - most of those can go across 2 phases using their 415v tappings instead, so no problem losing the Neutral.

NEVER use the green/yellow Earthing (Ground, USAn) wire for carrying load current, it's there to keep you safe! If used for load and a Disaster happens, e.g. a short to the machine frame, it's intended to keep the conductive parts (and anybody touching them) at local earth voltage (e.g. no volts at all!) so no current flows through you, the user, then the current should either blow a fuse/breaker or (the safer way) trip the RCD/GFI - if load current is passing through, the earth resistance can be enough to raise the machine to a dangerous voltage although it *SHOULD* trip the RCD/GFI - I've experienced this on green Chinese machines sold here in England with faulty electrics and high-resistance cables direct from the factory... Other importers may be as bad or worse.

The UK changed from 240 to 230 as well, "harmonising" with Europe, but there's a 5% supply tolerance on that 230v, a lot of folk in the UK complained that they weren't going to get the same power per amp and so it would put up prices, then it was explained that the voltage was staying at 240 as 230 + 5% = 241v, similar in the EU, 230 - 5% = 219v... SO everybody's happy, and the Eurocrats get to enjoy long sessions in council with 5-star meals and hotels on their expense accounts, making up more regulations that make no difference to anybody's lives :)

One bit of info' re line frequencies, Europe's on 50 Hz, has been since the 40s/50s, as far as I know it's only the US and the "Pacific Rim" countries that are on 60Hz - and using 60Hz kit on 50Hz is more of a problem than the 5% voltage difference, as transformers and induction motors are "Volts per Hertz" devices and need lower applied voltages for the same current at lower frequencies (somewhere between 15 and 20% lower) - which is why USAn kit sometimes blows on everywhere else's mains, probably why the Asian devices blew, designed for 60Hz? As an example, exporting UK 415v 3-phase kit to the USA works, as their 460 - 480v at 60Hz gives near as dammit the same current, coming back the other way ditto, as their 460-480v kit's being fed 380 - 415 so stays within current ratings - not so good going from 220/60 to 240/50 though, where it should be running closer to 200v... Lets the Magic Smoke out for good :(

Dave H. (the other one)

P.S. - Glossary!

RCD - Residual Current Device (sometimes "Disconnect") - has phase and neutral conductors passing through it inside a transformer, any imbalance between phase and neutral currents means current is going somewhere else, i.e. to earth so there's a fault - it trips and disconnects the phase and neutral to keep the appliance / installation safe, usually at 30 milliamps as that's been ruled the max safe current a human can take in about 99% of electrocutions.

GFI - Ground Fault Interrupter - much the same but translated into USAn!
 
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Glad you know what you are doing, electricity was not my best subject when I studied marine engineering, sure I get the basics of generation and distribution, even fault finding and repair on a known system, but when it comes to wiring up motors onto a system that is different from their name plate, I'm well out of my depth. BTW your 5 wire 3ph plug woud have been L1, L2, L3, N and E. If you leave the blue out that is the N does that mean you are usinhg the E (yellow/ green or just green on older stuff ) as your N. Are you wiring star (WYE) or Delta?
Hi Bob,
Yes sir, the green/yellow is earth ground- there is no neutral being used, just 3 hots and a ground lead
90% of the stuff i work on is wired WYE, i have only a few pieces of equipment that use Delta wired motors
 
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