[bbrown01]

Hi Dave,

I measured the current with a Fluke 322 clamp meter. My electrician's clamp meter had the same value. I have only run the unit long enough to check the voltages and current. Maybe 15 min. Doesn't seem to get warm. The company claims it can be run continuously without load. I have been in touch with the mfg. and they said this is normal operation. I also have a test report that came with the unit with similar results.

-Brian

[slatern44]

I know I have posted this before but call your power company and just asked them if you can get 3-phase power. I was running on a rotary converter for about a month when one of my customers asked me why don’t you call PGE and ask if you can get 3 phase. So I did and 30 days later they put it in for FREE, I had to pay to re-wire my shop and the meter base but that’s it. Now two more shops down the road from me that were also running rotary converter also call PGE and they go 3-phase for free also.

[bbrown01]

Slatern44,

Thanks for the suggestion but I already tried that route. I applied for 3-phase from PG&E on Jan. 12, 2006. Not sure what it's like in Yamhill, but here in Santa Cruz county they are worse than the planning department. I've heard almost nothing (except for personnel change notices) from them since my application. I think I'm stuck using a phase converter.

[slatern44]

I understand, I also got told no the first time that why I got the rotary converter. If you do try it again make sure you talk with someone in the service and design department because they are the one that will draw up the plans and get them approved.

[gar]

080406-1832 EST USA

bbrown01:

Did you read and in any way understand what I said in post numbered #2?

Current and power are not the same thing. Instantaneous power is the product of the instantaneous current and voltage of a load. If you multiply sin b * cos b and average this over one full cycle what is the result? Suppose v = Vp * sin a, and i = Ip * cos a, and you let p = v * i and average this over one cycle to determine average power what is the result?

Go find yourself a wattmeter and measure your input.

.

[Andre' B]

Probably the converter has a really bad power factor when at idle. Which would mean the current you were measuring was not real but reactive current. Over simplified reactive current cycles back and forth between the device and the power grid and does not transfer any energy.

http://en.wikipedia.org/wiki/Reactiv...apparent_power

If that thing was pulling that much real power at idle it would melt down in a short time.

[bbrown01]

Hi gar/Andre' B,

I did read it but admit I didn't follow you and still don't quite understand. But I'll take your word for it. The way it was explained to me by the vendor today is similar to what Andre' B described in #26. I just wrongly assumed that anything drawing that much current was consuming a lot of power. I'm just hoping that while the machine is idle the converter is not consuming a lot more in addition to the machine.

I'm still concerned that when the converter switches from low to high mode and back that doesn't introduce some anomalies at the machine. I agreed with the vendor I would hook it up and try it before coming to any conclusions.

Thanks for your help.

-Brian

[gar]

080409-1820 EST USA

Brian:

In an AC circuit with a sine wave voltage excitation a resistive load (absorbs power --- heat) has a current that is a sine wave also and in phase with the voltage.

Instantaneous power is p = v * i and this can be written as p = (V*sin x) * (I*sin x) where V and I are constants. p = V*I * (sin x * sin x). From trig identities we have sin x * sin x = 1/2 ( 1 - cos 2 x ). If this is averaged over one full cycle the result is 1/2, then Pave = V*I/2 . Note: V and I here are the peak amplitude of the waveform. The RMS value of a sine wave is the peak value divided by the sq-root of 2 (1.414) and the inverse is 0.707. The above Pave becomes 1.414 * Vrms * 1.414 * Irms /2 or Vrms*Irms*2/2 or simply Pave = Vrms*Irms.

Change the load to a capacitor and there is essentially a 90 degree shift of the current relative to the voltage. Capacitors can be nearly ideal in this respect. Now the instantaneous power equation can be written as p = V*I * (sin x * cos x ). The trig identity here is 1/2 (sin 2x). Average this over one full cycle and the result is 0. Therefore, in an ideal capacitor load there is no power dissipation and no heat.

Things are not that good with real components, and inductors are nowhere as lossless as capacitors.

Conclusion: your load may pass a large current, but without more information about the load you do not know how much power is consumed in the load.

You can probably use your watt-hour meter as a means to approximately measure the power consumption of your converter with and without the CNC load.

For trig identies see "Handbook of Mathematical Tables and Formulas" by Burington.

.

[gizmo_454]

Keep trying for that 3 phase power! That sounds like a ton to me!! Granted I am in Michigan, but we run our Mini Mill, SL-10, 4 X Brown & Sharpe screw machines, other misc equipment, and all of our 110 (including air conditioning in the summer) for about $400 in the summer and $350 in the winter!!! But we have 480 3 phase power from the pole and run a 30 KVA 480 to 208 3 phase transformer.

It's the way to go if you can get them to give it to you! Keep trying!!!

Gizmo

[Matt@RFR]

Keep trying for that 3 phase power! That sounds like a ton to me!! Granted I am in Michigan, but we run our Mini Mill, SL-10, 4 X Brown & Sharpe screw machines, other misc equipment, and all of our 110 (including air conditioning in the summer) for about $400 in the summer and $350 in the winter!!! But we have 480 3 phase power from the pole and run a 30 KVA 480 to 208 3 phase transformer.

It's the way to go if you can get them to give it to you! Keep trying!!!

Gizmo

PG&E said they would gladly run 3 phase to my house for me. It'll only cost $8,000.00 per mile, and the nearest 3 phase is 9 miles from us.

It's one thing if you can convince them that your area could, at one point, become industrial-use land due to expansion, but beyond that, you're screwed.

[bbrown01]

Hi Matt,

I have 3-phase running along side my property. They just need to string a 3rd primary wire (about a 1000 feet) into my property and swap (or add) a transformer. I even offered to pay for the upgrades. They're just not interested.

Did you happen to record the measurements for the current on the 3-phase side when you made your measurements on the single phase side in your 1st post?

[gizmo_454]

PG&E said they would gladly run 3 phase to my house for me. It'll only cost $8,000.00 per mile, and the nearest 3 phase is 9 miles from us.

Ouch!!!!(chair)

I suppose you could run for a number of years with the elevated costs and still not have paid that much!!!

Good luck with your situation!!

Gizmo

[rickyt]

In Ga. my power company said $100,000 per mile. I live .5 miles from the nearest source.

[gar]

080416-0729 EST USA

matt:

If your meter has a rotating disk you can use it as a power meter.

Shut off all power in your house, clocks do not matter. The disk should be virtual still. Connect a known load, like a 1500 W heater to any socket. For 10 seconds, or 60 seconds, whatever is appropriate, count the number of revolutions of the disk.

Remove the calibration load, and run your phase converter without any machine connected. Use the same time period and count revolutions. If twice as many revolutions, then the standby power consumed by the converter is twice your calibration load.

Next you can put your machine load on the converter, do whatever heavy cuts you want as a test, and while the cuts are being made monitor the disk rotation.

.

[gar]

080416-1329 EST USA

I just did a quick check on my house meter. I am guessing my current load at about 2 KW. Time for one revolution was 14 seconds. I will do a more accurate check later.

So maybe a better experiment is to measure time for 1 or 2 revolutions. Since there is a big black mark for once per revolution it makes more sense to measure time for an integral number of revolutions than revolutions per time unit.

.

[Donkey Hotey]

I just thought of something really cool last night. Wouldn't it be nice if you could special order a rotary screw compressor with a 30 HP motor and a 7.5 HP pump? You could start it on a static phase converter, then use the surplus energy as your RPC.

You'd get high CFM, low noise, clean air and reduce power consumption (not running an RPC and an air compressor).

[gar]

080418-106 EST USA

A little closer calibration on my watt-hour meter.

I did not get all the residual load off. However it was moderately small. I Used a 1500 watt resistive load. If the residual was 500 W, then 2 KW was 20 seconds for 1 revolution. My meter is a 240 V 200 A calibrated at 50 A.

Matt can you run this type of experiment.

.

[larrycoyle]

I have two rotary phase converters running in my shop and they pretty much run close to twelve hours a day at least five days a week. One is a 40HP CNC phase converter that runs my 5-axis FIDIA and the other is a 30HP that runs my 15HP Ingersoll Rotary Air compressor. That along with the air conditioner that runs constantly and my highest electric bill is around $350.00. The phase converters are GWM and are made in Missouri. They are damn nice too. It sounds as though you have something else going on in the woodpile.

[PhaseChangeConv]

For anyone in Australia who is looking at a Phase Converter, visit www.phasechanger.com and check out the PhaseChanger. They run at a 95-97% efficiency, so there is very little extra power lost through contactors and capacitors within the unit itself. Unlike most rotary converters, we use electronic switchgear and havy electronic circuitry to change the level of capacitance within the converter in order to keep up with the current load bearing on the unit within 5ms brackets.

Feel free to contact me on [email protected] if you have any questions, even for our American friends. I am happy to answer any you do have.

[bob1112]

For anyone in Australia who is looking at a Phase Converter, visit www.phasechanger.com and check out the PhaseChanger. They run at a 95-97% efficiency, so there is very little extra power lost through contactors and capacitors within the unit itself. Unlike most rotary converters, we use electronic switchgear and havy electronic circuitry to change the level of capacitance within the converter in order to keep up with the current load bearing on the unit within 5ms brackets.

Feel free to contact me on [email protected] if you have any questions, even for our American friends. I am happy to answer any you do have.

Are you saying you you can maintain 95% eff from 0-100% load? You have an interesting product that seems to cover the problem of how much capacitance to have in a converter, but how do you counter the costs of one running at idle? Most converters than are decently balanced run at 90%+ eff with 60-80% load, but what about idle?