Go Down

Topic: Solid State Relay latches due to low current problem (Read 710 times) previous topic - next topic

Paul__B

Fluorescent lights have a capacitor in them to bring up the power factor onto the real axis because household meters can only registers power projected onto the real axis.
Wow!  :smiley-eek:  That is new!

Whatever happened to the good old fashioned Ferraris/ Bláthy meter which automatically compensated for the power factor?  I thought that was the standard - at least in my lifetime here.

(Apparently things must be different in England.  :smiley-roll: )

gilshultz

Yes the data sheet says 2 back to back SCR's. We did that long before triacs were readily available at a reasonable cost at the ratings needed.  The data sheet tells the Holding Current - IH - 44 50 mA, that states you must have at least a 50mA load to keep it on.  You can put a LED and probably pick up the current you need. For many years and still today SCR's are used in many high horsepower DC drives. Try to find a triac rated at about 300A at 1000V, for use on a 3 Phase 550V mains to drive a DC motor.
This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

Grumpy_Mike

Quote
The data sheet tells the Holding Current - IH - 44 50 mA, that states you must have at least a 50mA load to keep it on.
Yes but that is not the problem the OP is having. His problem is that it won't go off.

MarkT

Wow!  :smiley-eek:  That is new!

Whatever happened to the good old fashioned Ferraris/ Bláthy meter which automatically compensated for the power factor?  I thought that was the standard - at least in my lifetime here.

(Apparently things must be different in England.  :smiley-roll: )

Obsolete because they can't report home.  Modern UK meters are all smart and take & report readings
automatically.  They've been rolling out for over a decade IIRC.

The old mechanical meters were subject to a lot of fraud as sticking a big magnet on them slows them
down.  Mechanical meters aren't very flexible for multiple-tariffs (although this has been done, ie
Economy 7 meters had two meter clocks driven from the meter movement on a time-switch),
Mechanical meters are useless for future requirements such as supporting load-shifting where the
cost varies across the day, and have all gone now I think (certainly they were due to be replaced by 2020)

Energy use monitors typically report the consumption live from the smart meter too.

Billing for apparent power rather than real power is a great incentive to have a sensible power factor
in the first place (bad power factors mean the power distribution infrastructure has to be rated more
conservatively, as higher currents are flowing - and more power is lost in wires). Highly reactive
loads cause instability problems in the distribution network too, so its important domestic electricity
use is kept relatively well-behaved (in the old days the bulk of the load was resistive heaters, not
any more...).

And smart meters measure real power and apparent and can support complex tariffs involving both
values (in theory at least - no idea if this is done).

Don't get me wrong, the old style electro-mechanical meter was a miracle of technology, its just that
it was essentially Victorian(*) technology and doesn't meet today's requirements.

(*) slight exageration, but not far from the truth.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

TomGeorge

Fluorescent lights have a capacitor in them to bring up the power factor onto the real axis because household meters can only registers power projected onto the real axis. If you remove the capacitor then you get two things:-
1) you run the light for free.
2) you break the law because it is an offence to do this.
Interesting, power factor capacitors here in Australia were only needed in industrial installations.
(Large numbers of factory lighting units)
Possibly to also make sure 3phase current balance.
Ahh those were the days, always a flickering "fluoro" somewhere in the building.  :) :) :)
Household fluoro batten units here only had to have the inductor to start them.
Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

Grumpy_Mike

Quote
Interesting, power factor capacitors here in Australia were only needed in industrial installations.
Yes that is true in the UK as well. But they work on a trip system, if you exceed the power factor for any time at all, then the whole quarter's bill has to be payed at the higher rate. This is an incentive for the industrial installation to spend a bit of money on the system.

PerryBebbington

Mechanical meters are useless for future requirements such as supporting load-shifting where the
cost varies across the day, and have all gone now I think (certainly they were due to be replaced by 2020)
Not all gone, I still have one. I refuse to have a smart meter. So far I have had £200 from the energy company for bullying pestering me to have a thick smart meter when I have made it clear I am not having one.

SouthernAtHeart

I'm glad to see I can buy a snubber circuit with wire leads, making it easy to add, and it won't look homemade rigged. 
This is the only one I can see that DigiKey carrys, it's 47ohm/0.1uF. Would that likely work?  You suggested 100uF.
Snubber circuit


There's also This one on Ebay which is 100ohm, but I'd rather buy from Digi-Key for quality assurance. But if the 100ohm is better, I'm sure it's probably fine.
Thanks

Grumpy_Mike

Quote
certainly they were due to be replaced by 2020
There you go, government targets, do you know of any target they have hit.

I too have not given it to pressure to have one. They can cut you off without your consent and then sack all the meter readers. Given how "good" the UK electricity industry is, the less control they have better.

Grumpy_Mike

#24
Oct 05, 2020, 06:18 pm Last Edit: Oct 05, 2020, 06:19 pm by Grumpy_Mike
I did say
Quote
You need to know by how much you need to bring this power factor down by. You then take the vector addition of the power factor of the two loads to find the final power factor of combining two loads.
So there is no way to know if a 0.1uF capacitor or a 100uF capacitor is needed for your circuit. Too much capacitance and you could just move the power factor the other way and it still wouldn't work. Too little and you do not shift it enough and so it still wouldn't work.

Can you measure the inductance of your motor?

SouthernAtHeart

I did say
So there is no way to know if a 0.1uF capacitor or a 100uF capacitor is needed for your circuit. Too much capacitance and you could just move the power factor the other way and it still wouldn't work. Too little and you do not shift it enough and so it still wouldn't work.

Can you measure the inductance of your motor?
I don't think I'd have any way to measure inductance with my Basic Fluke meter.  This is the little aerator that is being controlled
https://www.amazon.com/Marine-Metal-110-Air-Dual/dp/B002QFY3AU/ref=asc_df_B002QFY3AU/?tag=hyprod-20&linkCode=df0&hvadid=310563551669&hvpos=&hvnetw=g&hvrand=11632481323420744813&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=21142&hvtargid=pla-570854272258&psc=1

Grumpy_Mike

Quote
I don't think I'd have any way to measure inductance with my Basic Fluke meter.
And I know I can't tell the inductance of a motor by looking at a picture.

So, you could ask the seller a question, I would be astonished if he knows what he is selling but makbe he could get back through the chain of people he bought it off.

You could get a meter that would measure inductance. Or you could go with trial and error on the snubbers starting at the one with the smallest capacitor.

countrypaul

Could you find an alternate bubbler that would not show the same PF problem and would be strong enough not to cause an issue with the SSR?
Alternatively could you use a contactor to switch the bubbler and the SSR to switch the contactor - although I guess there is every chance the contactor would display the same problem?

Wawa

You suggested 100uF.
I suggested 1 uF, but that might be a top value.
0.1uF (100nF) to 0.47uF (470nF) is common for small loads.
$12 is very expensive. Pull one out of an old vacuum cleaner or kitchen appliance.

Resistor value is not important.
Leo..

Paul__B

The old mechanical meters were subject to a lot of fraud as sticking a big magnet on them slows them
down.
It would have to be a really big magnet to significantly add to those close to the disc.  :smiley-eek:

and have all gone now I think (certainly they were due to be replaced by 2020)
I think I still have one, and have seen many around still!

Don't get me wrong, the old style electro-mechanical meter was a miracle of technology, its just that

it was essentially Victorian(*) technology and doesn't meet today's requirements.

(*) slight exaggeration, but not far from the truth.
According to Wikipedia, "Victorian" is perfectly correct.  :smiley-lol:

Go Up