Who Invented Three-Phase?

Uh, Mr Scott of Scott Tee fame begs to differ with you.

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-- Many thanks,

Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss:

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You can get extra phases, provided only that you have more than one to start with.

Best regards, Spehro Pefhany

Actually Tesla only worked for Edison for a short time when he arrived in this country. Edison promised him money to fix a certain electrical problem and after Tesla fixed it, Edison told him he was joking! Tesla took off never to return.

Yes, it's true Edison was just an experimenter who didn't understand the theory and engineering the way Tesla did. His inventions were, however, high impact if not high tech! Sure ideas like the light bulb, the phonograph and movies were mostly mechanical experimentation and trial and error, but there is no denying the HUGE impact these few devices had on 20th century life!

But oddly enough it was Edison's tendency to to hire bright people and take credit for their work that was his greatest invention and the one he almost never given credit for! I'm talking about the modern industrial R&D lab. Today virtually all industrial research labs are set up on the Edison model! The "Tesla" model of the brilliant loner inventor has all but vanished (with a couple of notable exceptions such as Steinmetz at GE and some others)

They can give you a second set of three phases, shifted from the input three phase set by 30 degrees (or multiples thereof). This is accomplished with a wye-delta transformer configuration.

A standard three phase input to a full wave rectifier gives you six pulses per cycle. Add one wye-delta transformer and you get a twelve pulse rectifier. Add a seconf wye-delta (connected to shift 30 degrees the other way) and you get 18 pulses per cycle.

Each three phase group has 6 rectifiers (same as the number of pulses).

More pulses per cycle, smaller valleys to fill. Less caps needed.

Sure, but I bet there's a lot more three phase motors than 3 phase DC supplies in the world.

I wonder what percentage of electrical power goes to spinning motors, versus other stuff, (lighting, heating, entertainment).

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The only thing I remember from my power class was that 3 phase gave constant torque, so I always assumed this was what you wanted on big machines

If you add the squares of the sines of the three phase angles (at 120=20 degrees), for any angular rotation, it will be always 1.5. This means = that=20 the total power will be constant. Torque is proportional to Power/Speed. =

Speed is generally proportional to voltage, and torque is proportional = to=20 current. So three phase will provide constant torque.

Paul=20

The sum of all three phases is always 1.0; i.e. the power does not vary over the length of a cycle. This makes 3ph good to rectify; far less filtering needed for DC.

On a normal three core three phase transformer, the zigzag arrangement can generate the number of phases.

The secondary winding for a "new" phase will start on one core and continue on a different core (phase), thus the induced voltages are added in vector form. By varying the amount of turns on each of the cores, all the required phase shifts can be generated on a single transformer.

The simple 6-pulse rectifier will have quite ugly current waveforms, causing harm in the feeding distribution systems. The 12- and especially 18-pulse rectifiers are much more gentle to the feeding network, by drawing nearly sinusoid current from the network.

If your 'six-phase' is coming from tha three-phase transformer, swap two phases on the transformer primary.

A lot more iron in the transformers, though.

That was very important in computer mainframe days.

/BAH

The constant power characteristic of 3-phase means you can make an isolated unity power factor SMPS with no bulk storage capacitor, with 98% efficiency reported by the inventor of this configuration, Dr. Slobodan Cuk of TESLAco (Oct 2010 Power Electronics Technology).

Tesla, being actually smart, invented "Polyphase," covering all bases.

If someone insinuates that 90deg polyphase was Tesla's invention, while 60deg polyphase wasn't ...well ...it's a polyphase patent, not a 90deg polyphase patent.

Nope, because the whole point of polyphase was to power Westinghouse corp polyphase motor.

The patent package sold by Tesla included the modern AC induction motor and the modern AC power grid.