I wish I understood more of your dissertation on 3-phase power

This makes me wonder–I just moved from an industrial space to a regular apartment. I was not aware of anything about 3-phase power, but the outlets in the space were definitely not the normal kind, and it used to house a printing operation, so perhaps I had 3-phase power without knowing it.

Now I run my industrial sewing machine on decidedly non 3-phase power. Am I doing it permanent damage?

All three phases are stepped down in the US to 115 V (plus or minus 5) for residential use. For most applications, you are only using one phase and the neutral line. For others, you are using two phases (A and B, for example) but not the neutral; the vector difference between these is 208 V (find the square root of the sum of (120 + 120*sin(30))^2 and (120*cos(30))^2). In fact, whether you use A and B, B and C, or C and A, the vector difference is always 208 V.

The other way to operate is to use multiple phases. These are strangely referenced by doubling the single phase voltage (2 * 110 = 220, 2 * 115 = 230, 2 * 120 = 240). There may be some esoteric reason for picking one over the others, but if you read the fine print on your machine, they will typically say something like “230 V +/- 10″ or “220-240 V”. A two phase machine is using AB, BC, or CA and probably the neutral.

A three phase machine is using all three phases but probably not the neutral. The phase order may matter, especially on motors. For example, if it is designed to run ABC and the electrician hooks it up ACB, it may run backwards (or the smoke may run out). Phase order is only a matter of swapping two wires (note that ABC is the same as CAB and BCA, but the opposite of ACB and its twins CBA and BAC, and there are no other choices).

The reason for using higher voltages and multiple phases is that power is equal to current times voltage times # of phases. All things equal, a machine using 220 V, 3 phase power will have much lower average current than one running 115 V single phase. Current creates heat in wires, and heat reduces the reliability and lifetime of the equipment. It also adds to your misery and/or cooling bill.

BTW… I’m moved into the new house. I still haven’t invested in any fusing devices, yet. But, I did already ask an electrician about hanging a 110v raceway (my knife uses 110, btw). He just sighed and said, “yes, it’s possible”. So, it’s not just a ‘girl thing’ they all have their perceptions and need persuasion. My guy just doesn’t quite grasp what I’m doing, either. I keep explaining; but, I think he just needs to see it.

This coming weekend, I’m staining and (hopefully) sealing the basement concrete floor before unpacking and setting up the equipment. After I roughly locate the equipment, I’ll bring out the electrician. And, yes, I’ll put the knife on the table so he can see why I’m asking for a raceway.

Two comments:

In my recent search for a bar tack machine, I’ve been told that computers themselves on computerized bar tack machines generally take a wacky and funny electrical input. I’m told that this means that converting them from 220 3 phase to 110 is prohibitively expensive.

Second, I doubt that anywhere else in the country is as expensive as NYC is to have 3 phase wired into a building. It might cost me $10k, but I really doubt that is a valid indicator of the cost.

I do have a question: The folks who I will probably purchase my bar tack machine from believe that I can run a heavy duty static phase converter, and that I don’t need a rotary phase converter. Does anybody have a solid answer on that?