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3-ph current draw results
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Geoff Shepherd
Hi all,
Mainly out of curiosity, today I purchased a basic digital clamp-around AC ammeter ($60 Sperry DSA-400) to check the current draw on my Kay Phasemaster and Felder machines. The Phasmaster MA-1's original factory test results from two years ago show it should draw at idle 4.6A at 242VAC. My measurements show about 4.2A at 245VAC. Although this meter doesn't have a peak hold function, start up surge looked to be around 50A over several tests, but I don't know how accurate it could be in measuring these very brief surges. Since I only have only one twist-lock receptacle installed at the moment, I can only test each machine running by itself. Here are those results as measured on the single-phase supply to the phase converter: AF-22 LN 3kW/3ph (3m of 120mm hose connected to saw, 3m of 80mm hose connected to shaper, and a used but freshly cleaned pleated poly drum filter): Starting peak: ~50A Full power: 7.0A (8A with 120mm hose removed) BF6-31 2.2kW/3ph (table saw mode w/12" stock blade): Braking self-test: 4.9A Starting peak: ~40A Idling: 4.5A Remember - these results are with both the subject machine and the phase converter running. I'm not sure if I should just subtract out the phase converter idle current to get real values, or if it is more complex than that. When I get the second twist-lock recptacle installed, I'll check the 3-phase voltage balance under load and 1-phase current draw with both the BF6-31 and the AF-22 LN running simultaneously. The single-phase amp measurements were taken on each of the two hot legs inside my 30A quick disconnect to the phase converter. Curiously, there was a consistent difference about about 0.2A between the two hot lines. I'm not sure what would cause that, but maybe it has to do with the snap-clamp transformer being proximity sensitive to the metal cabinet, or just the results of not buying a more expensive meter. In any case, I took the two measurements and calculated an average. If I did this incorrectly, please somebody let me know. I'm also not sure how I should measure the current draw on the 3-phase side. Do I measure one leg, two legs, or all three and add/average the results? Not sure... ..Geoff |
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Charlie Norton
The 7.0A you measured was the current flowing to the phase converter after
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the split between the machine and the converter itself, so this is the amount of current required to generate the third phase. When you measure the three phase currents out, you will probably see the difference between the 7A and the 4.2A idle. I am always surprised at how much power the converter takes at idle. I would be curious to see how much current is flowing into each of the 3 phase legs. I wonder if the generated phase current is much different than the other two. Has anyone ever looked at the currents out of the phase converter with a current probe and an o-scope? Do they maintain anywhere near a 120 degree phasing between the three phases? Is the phasing dependant on load? -----Original Message-----
From: Geoff Shepherd <geoff@...> To: felder-woodworking@... <felder-woodworking@...> Date: Sunday, February 20, 2000 10:23 PM Subject: [felder-woodworking] 3-ph current draw results Hi all,Phasemaster and Felder machines.3-phase voltage balance under load and 1-phase current draw with both the BF6-31and the AF-22 LN running simultaneously.felder-woodworking-unsubscribe@...
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Geoff Shepherd
Charlie,
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I think I left out a bit of info... my two-pole quick-disconnect supplies single-phase power both to the converter as well as contributes two hot legs to the machines. The third leg comes from the converter and joins the original two hot legs. Shutting off the QD cuts all power to the converter and machines simultaneously (no chance of single phase going to the machines unless the converter failed). In other words, as I was measuring at the quick-disconnect, I was measuring the combined load of the phase converter and the powered machine(s). Check out John Renzetti's three-phase wiring diagram in the group Vault, it's what I have done for now: ,%20News,%20and%2 0Reviews/Technical%20Information/3-Phase%20Wiring%20Diagram%20-%20J%20Renzet ti.gif (yow, that's long... you might have to cut'n'paste if it doesn't work) At some point, I may do a fancier set up with a three-phase load center so I can do the automatic dust collector thing. So, last night I got my second receptacle installed and measured the combined load of the phase converter, AF-22LN, and BF6-31. That came out to about 10.5A at the quick-disconnect. I imagine it should be a bit more when the BF6-31 is doing some actual work such as planing 12" wide stock (I'll take that measurement too, just for completeness). I think John's phase converter (same model I have) is cooler running than mine - it uses only a couple amps at idle. Since mine uses about four amps at idle, it does act as a small room heater - can't complain this time of year. The future in phase conversion will probably be these microprocessor controlled inverting-type systems I keep hearing about. Didn't someone on this list retrofit a BF7-41 with one of these? I wonder how the efficiency and cost/benefit ratio is... ..Geoff ----- Original Message -----
From: Charlie Norton <cnorton@...> To: <felder-woodworking@...> Sent: Monday, February 21, 2000 8:16 AM Subject: [felder-woodworking] Re: 3-ph current draw results The 7.0A you measured was the current flowing to the phase converter afterthan the other two.AC showammeter ($60 Sperry DSA-400) to check the current draw on my KayPhasemasterand Felder machines. Iit should draw at idle 4.6A at 242VAC. My measurements show about 4.2A at wascan only test each machine running by itself. Here are those results as3-phase nota consistent difference about about 0.2A between the two hot lines. I'm onesure what would cause that, but maybe it has to do with the snap-clamp felder-woodworking-unsubscribe@...leg, two legs, or all three and add/average the results? Not sure...felder-woodworking-unsubscribe@...
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