Half rectifying mains...

[Externet]

Hi.
Read somewhere that using only half wave was 'prohibited' by power supply companies... Is that right ?
What does to the mains network/metering consuming only half wave of the (120VAC) supply ? Example: rectifying feed to a plain incandescent light bulb with a 1N4007 diode.

 

[KeepItSimpleStupid]

A half-wave system would disrupt the power factor, so the only possible way that would upset the utilities is if it were a high power half wave rectifier.

A system that I used and troubleshot needed 15 kV DC at 1.5 Amps. That was done with 3 phase. The device required, I think 50 A 208 VAC 3 phase. Another similar system required 90 A 208 VAC 3 phase.
Fortunately, I got mad at it and spent a lot of effort fixing it, so the HV regulator wouldn't break again. My predecessor just replaced the same parts.

 

[MikeMl]

I think that the power company dislikes it if you draw DC from their grid, which is what a half-wave rectifier would do. It creates harmonic distortion, and forces direct current through transformers.

 

[alec_t]

You use one half cycle and persuade your neighbour to use the other half cycle. That should keep the utility company happy .

 

[ericgibbs]

Many years ago in the UK, all TV sets were connected directly to the mains supply, using half wave rectification for the HT supply. [ Valve/tube supplies ]

It caused a number of problems for the mains power providers.

 

[Nigel Goodwin]

Many years ago in the UK, all TV sets were connected directly to the mains supply, using half wave rectification for the HT supply. [ Valve/tube supplies ]

It caused a number of problems for the mains power providers.

Exactly, it was a requirement from the power companies that TV's (and other equipment) stopped using half wave rectifiers.

Obviously one or two TV's wasn't a problem, it was millions of TV's all using half wave rectification.

 

[Pommie]

Don't know if they still are but the last hair dryer I pulled apart (long time ago) used half wave for the warm setting and bypassed it for the hot setting.

Mike.

 

[MikeMl]

Don't know if they still are but the last hair dryer I pulled apart (long time ago) used half wave for the warm setting and bypassed it for the hot setting.

Maybe they made a deal with the power companies...
Half the millions of units they shipped have the diode pointing one way, and the other half have the diode pointing the other way....

Why couldn't the TV makers do that?

 

[Nigel Goodwin]

Maybe they made a deal with the power companies...
Half the millions of units they shipped have the diode pointing one way, and the other half have the diode pointing the other way....

Why couldn't the TV makers do that?

Because it would have been a silly idea

And obviously rely on everyone connecting their sets the correct way to the mains.

FAR better to have simply fitted bridge rectifiers, which also allows smaller smoothing capacitors.

The original usage of half wave rectifiers was back in the valve days, and normally used either valve rectifiers, or metal ones, neither of which was particularly convenient (or cheap) for use as bridge rectifiers. The advent of cheap reliable silicon rectifiers is what made it practical.

 

[AnalogKid]

I have lamp sockets that are pseudo-3-way. They have a series rectifier, and make off-dim-bright with a standard 1-way light bulb, incandescent or LED. While I don't stay up nights worrying about AEP's power factor, I do like the lower electrical noise and acoustic noise compared to a triac dimmer.

And years ago you could buy a rectifier packaged in a thin round button to drop into a lamp socket. A 100 W bulb made only 50 W equivalent light and it was a bit yellow, but it lasted forever. They were unmarked, so I measured them with an ohmmeter, marked the cathode, and installed them in an alternating pattern.

ak

 

[Tony Stewart]

I read on Wiki that nano optical antennaes or "nantennae" could become more efficient than PV panels and nanotube coated DVD's could be used as power generators ( 2014 Nobel prize in Graphene). But not lately seen anything lately.

Similarily, I haven't seen any utility companies or Electric Standards prohibit this. Obviously, the net DC load is bad for transformer saturation, but only if it is significant .

 

[MikeMl]

...And obviously rely on everyone connecting their sets the correct way to the mains.....

I keep assuming that your plugs are polarized, like ours are...

 

[Tony Stewart]

Because it would have been a silly idea


FAR better to have simply fitted bridge rectifiers, which also allows smaller smoothing capacitors.

Actually the half bridge powered DC motor as in the case of 1600W hair dryer, would cost a tad more with twice as much resistance wire to drop just for the DC motor as the average voltage matters here and the 50% duty cycle effectively doubles the series resistance free. ALthough this is not in constant use.

 

[Nigel Goodwin]

I keep assuming that your plugs are polarized, like ours are...

Anything remotely modern is, our plugs are 13A, three pin, and have integral fuses as well.

But back in ancient history, which is when we're talking about, there were various plugs in use - and as nothing came with fitted plugs even if you had modern plugs you still had to wire it the right way round

In any case, American plugs then were two pin flat ones, and reversible as well.

 

[Tony Stewart]

The biggest problems with power distribution are underground leakage shorts, Partial Discharge and internal Corona induced explosions and Fault Remenance without SMART ABB reclosure synchronization to start at the exact phase where it opened , to cancel the Remenance which otherwise causes saturation from excitation current adding and thus surge cycles that can last a minute on large DT's and power transformers noted by the extreme forces of humming magnetostriction.