May I ask a question about the single vs two phase stuff

[mbrooke]

Said it before- I'll say it again- one can spin a motor alone the other can not. To me anything other than one phase provides rotation information.

 

[jumper]

Said it before- I'll say it again- one can spin a motor alone the other can not. To me anything other than one phase provides rotation information.

Got an NEC, IEEE, or any other back up reference for that opinion?

 

[mbrooke]

Got an NEC, IEEE, or any other back up reference for that opinion?

Yup- the mere absence in the IEEE, IEC, JIS, ect. Show me a single phase (or two phase) motor with 2 hots and a neutral meant to be hooked up to a 120/240 volt source. Reality, or physics, is not an opinion.

 

[jumper]

Yup- the mere absence in the IEEE, IEC, JIS, ect. Show me a single phase (or two phase) motor with 2 hots and a neutral meant to be hooked up to a 120/240 volt source. Reality, or physics, is not an opinion.

So, the answer is no. Thank you!

We simply have various ways that produce single, two, three and other polyphase systems.

Twisting off to motors is silly IMO. I do not define a system by motor type. I define the system and pick an appropriate motor.

 

[mbrooke]

So, the answer is no. Thank you!

We simply have various ways that produce single, two, three and other polyphase systems.

Twisting off to motors is silly IMO. I do not define a system by motor type. I define the system and pick an appropriate motor.

If it was possible, it would be in the IEEE. Eliminating capacitors, shadings, and centrifugal switches is a step forward and if it could be done it would have been done so long ago. Motor types, like the induction motor created various systems like 2 phase, 3 phase, ect- because single phase has no rotation and gave zero power at certain points in time.

 

[jumper]

If it was possible, it would be in the IEEE. Eliminating capacitors, shadings, and centrifugal switches is a step forward and if it could be done it would have been done so long ago. Motor types, like the induction motor created various systems like 2 phase, 3 phase, ect- because single phase has no rotation and gave zero power at certain points in time.

Okay..........

Is this a way for a sparky to do a system analysis of a service or such and determine voltage and type?

Or is this just a tangent. I like tangents personally, but help me out here.

Is hooking up random motors of various designs/voltages/etc a way to determine what type of service one has......

 

[mbrooke]

Okay..........

Is this a way for a sparky to do a system analysis of a service or such and determine voltage and type?

Or is this just a tangent. I like tangents personally, but help me out here.

Is hooking up random motors of various designs/voltages/etc a way to determine what type of service one has......

As you know sparkies have the tools which show the evidence of multi phase vs single phase, ie a voltage thats not double the L-L voltage hinting at phase displacement. There is also a phase rotation meter. More technically one can get hold of an oscilloscope.


But my point is that induction motors played a huge part in popularizing poly phase systems, for the exact reason that when one phase is at zero volts/amps, another phase is delivering power. In split phase all phases are delivering the same amount of power at the exact instant.

 

[mbrooke]

Okay..........

Is this a way for a sparky to do a system analysis of a service or such and determine voltage and type?

Or is this just a tangent. I like tangents personally, but help me out here.

Is hooking up random motors of various designs/voltages/etc a way to determine what type of service one has......

For example, look at this:

The first image would technically be a 4 phase system since we not only have 90* but 180* differences as well.

 

[jumper]

As you know sparkies have the tools which show the evidence of multi phase vs single phase, ie a voltage thats not double the L-L voltage hinting at phase displacement. There is also a phase rotation meter. More technically one can get hold of an oscilloscope.


But my point is that induction motors played a huge part in popularizing poly phase systems, for the exact reason that when one phase is at zero volts/amps, another phase is delivering power. In split phase all phases are delivering the same amount of power at the exact instant.

For example, look at this:

The first image would technically be a 4 phase system since we not only have 90* but 180* differences as well.

No, I am not going to get distracted.

How and what method do you determine various voltage systems/types? Pretend you are 3 year apprentice with some proper training. You get a Fluke multimeter.

Getting my point yet.

 

[mbrooke]

No, I am not going to get distracted.

How and what method do you determine various voltage systems/types? Pretend you are 3 year apprentice with some proper training. You get a Fluke multimeter.

Getting my point yet.

138 volts instead of 120 would be a give away...

 

[jumper]

138 volts instead of 120 would be a give away...

Among other significant readings that would determine another system and voltage if different.

And we have established parameters for those readings to make that determination.

We have proper descriptions of these systems......well mostly.

Reference determines the context of the readings.

As Mivey said “It really is that simple.”

 

[Besoeker]

the picture represents somebody's misunderstanding electrical theory - I've explained how it works.

Measure it with a 'scope. Then tell me I don't understand.

 

[mbrooke]

Among other significant readings that would determine another system and voltage if different.

And we have established parameters for those readings to make that determination.

We have proper descriptions of these systems......well mostly.

Reference determines the context of the readings.

As Mivey said “It really is that simple.”

All correct- and I think single phase is the correct description for 120/240 IMO. :angel:

 

[jumper]

All correct- and I think single phase is the correct description for 120/240 IMO. :angel:

Yes it is and.........yes I can get three distinct or individually unique voltages/signals/information from that system. Does not change the system type. No.

I am not trying to bust chops here but clarify/simplify for some poor simple future reader.

Assuming the person made this far before screaming “Egads” and ran off.

 

[Besoeker]

All correct- and I think single phase is the correct description for 120/240 IMO. :angel:

But what you have is 120-0-120.

 

[mivey]

For the "180 degrees apart" camp, say I have a device that measures voltage versus time between points A and B. And say I have two of them, and I hook up the second one with the leads reversed, so now I can compare the two graphs. What would you call the relationship between those two graphs?

Cheers, Wayne

Using the same two terminals? A change in polarity.

A polarity swap is two different looks at the same voltage between the same two terminals. One voltage is exactly opposite of the other because it must be: there are only two terminals.

The voltage from the two transformer windings is close but the two halves actually differ slightly because they are not perfect mirrors of each other.

It takes at least three terminals to get two different circuit paths. Now we have the possibility of two different phases at the same time in the circuit.

I've said this before but I'll repeat for this discussion:

The reference can be selected to increase or decrease from a point. The field strength grows across every little piece of winding and any point can be selected as a voltage's reference. Positive direction can be up the winding, down the winding, or away from a point along the winding.

Phase is a location on a waveform. For multiple signals of the same magnitude, shape, and frequency, if the value for any signal is located at a different spot on the waveform than one of the other signals, there is more than one phase present.

Suppose I pick the positive peak.

If both waveforms experience their positive peak at the same instant in time then they are in phase. This is the case with the N-X1 signal and X4-N signal. One signal has an X1 reference and the other has a N reference.

If one waveform experiences a positive peak at the same instant in time that the other experiences a negative peak, then they have a 180 degrees phase difference. This is the case with the X1-N signal and X4-N signal. Both signals have an N reference.

The flux may produce different results for different circuits. Think about a 2 diode full-wave bridge rectifier using a center-tapped transformer. The flux passes both winding halves but produces current in only 1/2 of the winding for 1/2 of the cycle and produces current in the other 1/2 of the winding for the other 1/2 cycle. The circuit currents are both positive (with positive away from center) waves occuring 180 degrees out of phase.

The transformer in this case is supplying the circuit two voltages with a 180 degree difference. You could get the same from one generator shaft with two windings rotated 180 degrees from each other.

 

[mivey]

Yeah I get it but please explain it in a way that a seasoned apprentice with skills could understand. Nothing beyond that please.

Can we call single phase center tapped tranny two phase? No. NEC wise? Again no.

Can we identify three distinct voltages/signals from certain single phase systems? Yes.

For a 120/240 set up. Two 120v and one 240V. Is this 2 phase? Is this 3 Phase? No to both.

Goldy, you are way smarter than me, these are rhetorical questions but since you are smarter than me, I figure you know that.

C.P. Steinmetz was one of the founding fathers of AC systems and a recognized genius.

He recognized that there were two phases present even if you could reduce the system of two smaller phases to a larger single phase system by taking one phase to be the negative of the other.

I don't recall the exact wording but I have his paper somewhere in my office.

 

[buffalonymann]

Watts is work performed. Voltage has to push that current.

Ummm (E)(I)=P therefore current is work

 

[Besoeker]

Ummm (E)(I)=P therefore current is work

Umm..............P=VIcosφ for single phase. You need a √3 in there if you have three phase.
Current isn't work

 

[mivey]

Ummm (E)(I)=P therefore current is work

To exchange enegy requires both an electric and magnetic field (voltage and current).

The cross product produces the Poynting Vector and shows the direction of energy flow.