Using a capacitor as a "wattless" dropper on 110 volt equipment?

the point is obviously to reduce v and/or i

Lots of appliances use a C dropper to supply varying loads. It's cheaper. Some loads need their v limiting with a zener, some can accept the variation.

the early ones just used a series lightbulb to the track, with IIRC 110v train motors. Yes, for children.

NT

I wasn't aware that it was common practice, I would have thought that in practical terms battery charging or similar might be feasible.

What loads are you aware of?

The power dissipated by the zener must limit the practicality of the Wattless dropper. A variation of any significance ie a few watts, would be better served by a transformer.

Happy days!

Would have been more fun with 240V.

AB

it's used in a huge range of things these days.

C dropping can be used with much higher powers than that, even over half a century ago it handled far more than a few watts.

It was 240v when a train wasn't running. Parliament was not happy.

NT

Well go on, enlighten me.

I cannot honestly see that it would have much place in anything but resistive loads with a very small variation in consuption.

Can you nominate a few examples?

I don't disagree. It could be used for an entire town or city as long as they all staggered kettle/ heater/ lighting/ shower use to a strict timetable.

C dropping never handled any Watt's incidentally, the clue is in "Wattless dropper".

Unchuffed perchance ?

AB

google is your friend

C droppers pass plenty of watts. They just don't dissipate them.

For sure

NT

Go on, I tend not to use Google, but even so Duck Duck is not exactly festooned with examples.

Google is no ones friend, it is only there to "rattle the stick in the swill bucket".

P = I^2 R

P = V.I.cos [phase angle]

The last capacitor I had experience of handling any Watts at all was many years ago when I stuck a 0.47uF 1kV in place of a Grundig flyback tuning cap. It handled about twenty I would say. The 21st melted it.

An electrolytic stuck in backwards will also demonstrate what happens when a capacitor "passes Watts".

AB

precisely, so approximately no dissipation, despite it passing plenty of watts to whatever's downstream.

NT

Rubbish!

It passes no Watts.

The only time a capacitor will "pass" Watts is when it heats up.

Current is Amps, not Watts

If a capacitor had anything to do with Watts, you would specify said value on ordering.

Please point out where you would buy a 10uF 5 Watt capacitor.

AB

Oh dear.

The other thing to watch is that some US stuff is really tight on the power rating for the transformer and it may be close to saturating the core when run at 50Hz instead of the designed 60Hz. Those crap mains electric razors they used to sell at Xmas relied on a 60Hz mechanical resonance to work. Sold in the UK they only lasted a couple of years.

You can get neat compact low power step downs intended for <50W loads. Or DIY as above.

Late to the party, you have checked that the primary isn't two 110 V windings in parallel haven't you? US mains is 110 V bi-phase and neutral, most stuff is connected phase - neutral (110 V) but big loads like washing machines at phase to phase (220 V). To be honest I'd be suprised if it does have two primary windings but you never know.

you mean Remington?

Never mind, dont worry. Apology accepted.

It's a simple mistake to make really, getting units mixed up. Who hasn't been guilty of confusing Angstroms and pH from time to time.

AB

I'm not sure why you're apologising to yourself, presumably for being a wally, but either way it's plonk time.

Never mind, keep up the search for those high power capacitors old bean.

AB

Its not Dave its just the one primary winding. It won't however be used that much and for that long it just got to twiddle a large FM aerial around.

Vid here by a yank "elmer ham;!

Yes they do one drives the motors at AC as best I can tell, the other 9 volt supply the microprocessor and display..

Thats what is in use at this moment. Pending the compact 230 volt step- down..

Indeed..

As you've surmised, the rotator motor is an ac only type (a universal ac/ dc motor will be unsuited on account of the interference produced by the commutator/brush gear).

It will be a 120v 60Hz induction motor but the thing you have to remember when running such motors off a 50Hz supply is that this makes them a 100v 50Hz induction motor. You have to scale the voltage down in proportion to the scaled down frequency to avoid excessive current draw along with the real possibility of core saturation which will exacerbate the increased I sq R losses in the motor windings.

TNP is in my killfile so I don't know what type of output his suggested "compact 230 volt stepdown converter" is. If it's just a 9v smpsu to power the electronics part, that won't be a problem but if it's a 230vac to 110vdc converter that'll just fry everything.

It seems to me unlikely that a compact switching 240vac to 110vac converter would be cheaper than a 50VA rated 240 to 100 volt autotransformer, especially one made up from a readily available (or to hand) 30 to 50 VA 240v split primary to 20v secondary transformer which you can use to get 120v minus the 20 volt secondary connected in 'buck' to get the desired 100v 50Hz motor supply.

Anyway, I just thought it might help to remind you about the need to scale the motor voltage requirement with the reduction of frequency when driving a 120v 60Hz motor off a 50Hz supply.

Don't think that would be a problem anyway your not normally using the aerial/s whilst rotating them.

I'm not a 100% sure it is AC it seems it might be. Haven't got it going as yet but hopefully soon, do appreciate the 50/60 Hz bit it won't be running that long or much either with the intended use.

It is AFAIK an AC one look like a small plug mounted type autotransformer

All noted I'll let everyone know how it goes when i get a aroundtuit!..