3-phase would mean no flicker, but at least two wires to control. Rather impractical...

Well, 3 wires for 3 phases, 1 neutral, And another wire for ground. 5 Wires is overkill for a little light bulb.

Here's a rough doodle i made of this new base.

For a 3-phase device you do not need Neutral - with symmetrical load (normal 3-phase load, like a motor or a 3-phase rectifier) there anyway flows no current and usually it is even not used at all (a 3-phase motor has 4 terminals - 3 phases and safety Ground; there is no Neutral; even the older 3-phase 4 pin sockets were meant exactly for such connection).

So if the Neutral is not needed, there is no difference, on what potential the 3-wires are, there is no principal need to have it on the ground potential. So it may be "positioned" so, one of the phase wires could be connected to Ground.

Today the European system uses grounded Neutral just because the desire is to have lower voltage (230V) single phase loads grounded on one side and at the same time allow the higher voltage (400V between phases) to be present for the higher power loads.

In the US many arrangements are used, one of them is having 240V between phase wires, but a center tap of one of the phase is as a "Neutral", so potentials not symmetrical.
That then allows connecting single phase 120V loads having one terminal at 0V level and 240V single phase symmetrical around 0V (these two are the same as single phase installations), plus full 3-phase (so circular rotational field) available for a 3-phase load (a motor or so).
Then the 3'rd phase then has about 208V against the "Neutral", a voltage level sometimes used as well.


And if the device does not require safety grounding (light bulbs do not), you do not need the Ground connection either.


So to just control the working, you then need just 2-pole switch connected in two phases. Of course, in OFF position the whole device remains  at the potential of the not switched phase, so safety-wise remains energized (to deenergize it, you need the full 3-pole switch).
That switch arrangement is used, when the switch can not be considered as a disconnecting device (e.g. with SSR or other solid state control devices), but rather just an operation control (so e.g. the 3-phase SSR's to control heaters or motors are made as 2-pole devices).


But anyway, having 3 wires and 2-pole switch as the minimum control and wiring is really ridiculous for a low power (less than few kW or so) lighting...

Such a weird lighting product would never be allowed in the UK simply because around 99 percent of homes in the UK are single phase it simply isn't permitted outside of large commercial buildings and then only if the total load exceeds 24Kw.

Well, it may be allowed, but no one will buy it...

Yeah right I think it's an extremely solution to a small problem

I seen somewhere in the gallery an experimental Mercury lamp with 3 Phase arc tube (star shaped with 3 electrodes). Pretty much what is described here. The gear to run it would be 3 chokes (a choke on each Phase)

I seen somewhere in the gallery an experimental Mercury lamp with 3 Phase arc tube (star shaped with 3 electrodes). Pretty much what is described here. The gear to run it would be 3 chokes (a choke on each Phase)

I wonder why it didn't get out of the experimental stage. It would only be useful if it was a crazy high power
bulb(50+Kw).

Quote from: Ash on February 11, 2016, 02:39:21 PM

I seen somewhere in the gallery an experimental Mercury lamp with 3 Phase arc tube (star shaped with 3 electrodes). Pretty much what is described here. The gear to run it would be 3 chokes (a choke on each Phase)

I wonder why it didn't get out of the experimental stage. It would only be useful if it was a crazy high power
bulb(50+Kw).

Im not expert at lighting technology but I would gess too complicated system. In high power aplications It would be much easier and more cost effective use just one choke with three phase input or phase to phase input rather than three separated chokes same also goes in low power aplication there probably where cost effectiness is much greater towards standart single phase system. In general there is no any benefits of using such complicated system.

I would also guess that star shaped burner is pretty difficult to manufacturer so that it has goof reliability.

Im not expert at lighting technology but I would gess too complicated system. In high power aplications It would be much easier and more cost effective use just one choke with three phase input or phase to phase input rather than three separated chokes same also goes in low power aplication there probably where cost effectiness is much greater towards standart single phase system. In general there is no any benefits of using such complicated system.

I would also guess that star shaped burner is pretty difficult to manufacturer so that it has goof reliability.

The 3-phase input will require 3 chokes, but that is not a reason for a 3-phase lamp to never make it for production.
The main reason woudl be with the too complex burner shape (3 power electrodes) and the fact the arc will rotate there (at twice the mains frequency) and not stay on one place.
Such high power lighting then evolved into DC arc tubes, where the ballast assembly then in it's simplest form contains those 3 chokes to limit the current and then 6 diode rectifier. The output of such rectifier is then quite nice, smooth DC current for the arc...

Quote from: Roi_hartmann on February 12, 2016, 01:48:36 AM

Im not expert at lighting technology but I would gess too complicated system. In high power aplications It would be much easier and more cost effective use just one choke with three phase input or phase to phase input rather than three separated chokes same also goes in low power aplication there probably where cost effectiness is much greater towards standart single phase system. In general there is no any benefits of using such complicated system.

I would also guess that star shaped burner is pretty difficult to manufacturer so that it has goof reliability.

The 3-phase input will require 3 chokes, but that is not a reason for a 3-phase lamp to never make it for production.
The main reason woudl be with the too complex burner shape (3 power electrodes) and the fact the arc will rotate there (at twice the mains frequency) and not stay on one place.
Such high power lighting then evolved into DC arc tubes, where the ballast assembly then in it's simplest form contains those 3 chokes to limit the current and then 6 diode rectifier. The output of such rectifier is then quite nice, smooth DC current for the arc...

Do you have any wave forms to show us? And how smooth does it have to be to properly drive a MV lamp?
I would imagine that a lightly smoothed  Full-Wave rectified single phase AC could be good enough.

The thought behind the 3 Phase burner is, that the arc never goes out so no reignition in zero crossing

The wave forms would be :

Phases


Rectifier outputs (open circuit)


Voltage across rectifier output (open circuit)


That is pretty good voltage without any smoothing at all, i think this easily could take 300V+ arc. But long arc DC lamp ? Somehow i dont think its going to work too well

When the current limitting impedance is upstream of the rectifier (in the form of three inductors or three phase compact reactor or so), the current sinewave will sum up to form the arc current. That means pretty smooth DC current (just about 10% 300Hz sinewave ripple), so no reignition at all.

With a means to provide some extra 150..200V for a cold cathode operation after ignition, a three phase 400V fed system could supply more than 400V of arc voltage load. The fact there is no zero crossing means there is no need forany reignition, so no need for the "factor of two" OCV margin usually needed for the AC arc systems, so just some small room for component tolerances is enough.

But when you replace the diodes by thyristors and some control electronic, you then put just a single choke behind the controlled rectifier and control the firing angle with a closed loop electronic so, the load current matches the desired value. With that you may supply arc loads easily up to 500V with the 400V three phase mains.

The cinema lamps use similar system, just the phase control regulation is separated from the rectifier by a transformer - as the arc voltage uses to be lower and currents higher (and it contain parallel branch with higher OCV plus a really HV ignitor  for the lamp start)...
And indeed the most modern ballasts use high frequency DCDC conversion instead of the phase control and the 50/60Hz transformer, offering mainly better mains power factor and harmonics and smaller, more compact size for even higher power levels...

We got here from the point of making reliable system by eliminating Electrolitic capacitors. Lets consider the reliability of what we have here now :

The rectifier after the chokes is not bad. There is no Silicon directly on the mains (which would be exposed to surges in the line voltage). The Silicon after the chokes is pretected quite well from the line by the big indicutance. Add a capacitor parallel to the lamp (some HV foil type, with big enough voltage margins to not degrade all the time from "self healing"), and the rectifier will be protected from the chokes kick in case of a lamp going out as well

The more complex Phase Control electronics - That is some power Silicon straight on the mains. Much more that can go wrong

Parallel to the lamp you can not add any capacitor - it tend to extinguish any discharge...

And regarding the semiconductors on the mains: Mainly with these high power devices that is of no problem at all. Because they have to be rather large to handle the currents, the currents causing the overvoltages are then relatively not that high anymore, so the components can handle them well and so clamp the overvoltages safely.

Moreover all semiconductors there are just thyristors and diodes - the two types which are virtually impossible to destroy (except when overheated; but that is rather difficult given their rating). The sensitive components are all types of the transistors. Not than they will behave much diferent from thyristors on an overvoltage event (got switched ON and then stay like that till the current disappear). But the difference is in the circuit around the thyristors is designed to remove the current externally to switch them OFF (commutation by mains,...), so when it activate itself, the circuit behaves just as if it was normally fired and after some time it deactivates it, so expect a spurious extra pulse on the load, nothing happens. With transistors the circuit expect it will be the transistor itself, to break the current in the circuit, so such uncontrolled activation then means a short circuit with consequent overcurrent and so destruction...

And to break the load circuit is rather impossible at those levels - an arc will form among the broken wires and so keep the path conductive. Only cause other probblems around. When there is current, the arc never extinguish. With "cycling" lamps the cause is not the arc breaking itself, but not being reignited after it get extinct by the zero cross current interruption. If such current interruption happens here, because of no current, there can not be any overvoltage...