small size (dimensions) capacitative load?

[sparkybird]

Hi everyone

I need to fit one of these

http://www.tlc-direct.co.uk/Products/DNCAPLOAD.html

but into a pendant light. Any ideas???

Thanks

SB

 

[toasty]

Try maplin or rs. They sell mains rated capacitors, I've used them in the past, put a bit of sleeving on the bare leads. Because they dont have those massive screw terminals they will easily fit in the pendant.

 

[sparkybird]

Toasty - thanks for speedy reply and great suggestion

Just been checking out RSS and it looks like the min voltage is 300V ac - does this matter?? Also I'm a bit rusty on the calcs and not sure what capacitance value I need. I need to have a min of 40W resistive load per light and I'm reckoning there being 9W CL's in the pendants

can you assist??

SB

 

[bernardgreen]

Capacitor 0.047uF micro Farads 250 volts AC in series with Resistor 100 ohms

Which come pre-packaged as a contact suppressor from RS Components

RS Stock No. 206-7847
Manufacturer Evox-Rifa
Manufacturers Part No. PMR209MB5470M100

There are other sources

 

[PrenticeBoyofDerry]

The link
http://www.tlc-direct.co.uk/Technical/DataSheets/Danlers/DNCAPLOAD.pdf

 

[bernardgreen]

My error. I assumed it was to absorb the capacitively coupled energet that makes some energy efficient lamps flicker or glow dimly when turned off.

It is probably the same circuit, a cap and a resistor.

 

[sparkybird]

Blimey, you guys are QUICK!!

Yes, Bernard that looks like the jobbie although it#s say's its out of stock until Jan 2012!! I need one next week!! I will hunt around based on that spec.

BUT, I would really like to know how you know it's that one - if you can spare the time an explanation (in fairly simple terms) would be great!


Thanks

SB

 

[sparkybird]

Too fast - the purpose of the capacitor is as Prentice Boy pointed out, to enable the time lag switches to function properly.... so what can you suggest?

Thanks

SB

Mind you, I do have a bathroom mirror light (flurry) which 'glows' in the dark even when switched off. It's a bit spooky at night - would fitting one of your originally suggested capacitors solve this??

 

[flameport]

Depending on how large that Danlers module is, you could fit a round dry lining box in the ceiling, put the module in there, and fix the pendant over the top.

 

[ban-all-sheds]

http://www.google.co.uk/search?q="power+factor+correction+capacitor"+fluorescent&tbs=ctr:countryUK

 

[bernardgreen]

Yes, Bernard that looks like the jobbie although it#s say's its out of stock until Jan 2012!! I need one next week!! I will hunt around based on that spec.

For stopping lamps glowing when switched off

RS ( should ) have a range of them with varying values, the actual capacitive value of the capacitor is not important as long as it is more than about 50 times that of the capacity between live and switched live in the cable to the switch.

BUT, I would really like to know how you know it's that one - if you can spare the time an explanation (in fairly simple terms) would be great!

The capacitor across the lamp and the capacity between live and switched live form a voltage divider ( when the switch is off ) so the lamp only sees a fraction of the voltage and not enough to glow.

First time was trial and error ( no error ) and then the maths to work out what capacity was needed. Then a rule of thumb that appears to work for up the 50 metres of switch cable. That is until more effecient lamps are developed that "work" ( glow ) on a volt or too.

For the application you have one would need to know how much current the switch needs when it is off before being able to calculate the necessary value of capacitor to put across the lamp.

 

[sparkybird]

Ummm, I think I follow... need to apply brain before a glass of vino...

The one I have (from Danlers) says on it

MKP41 X2
2 u (micro) 2
275 VAC
20/100/56/C

No farads on it though?

EH?

I suppose I could call Danlers tomorrow to ask the size

Thanks again
SB

 

[sparkybird]

Just found this (thanks Ban) for a similar product:


"Fluorescent lamp loads without power factor correction capacitor require a mains rated capacitor of a minimum value 220nF 250V a.c. (X or Y rated) in parallel with the load to be driven by 2031VETR.
Electronically ballasted fluorescent lamp loads will require a mains rated capacitor of a minimum value 470nF 250V a.c. (X or Y rated) in parallel with the load"

Will try and elicit the info from Danlers

Cheers

SB

 

[bernardgreen]

MKP41 X2
2 u (micro) 2
275 VAC
20/100/56/C

2u2 is the shorthand way to write 2.2 microFarads

Unlikely to find a contact suppressor with that size of capacitor.

Seems a bit large as its equivalent impedance at 50Hz is (approx) 1500 ohms which will absorb 150 milliamps at 230 volts. An apparent extra load of 35 watts when the lamp is switched on.

But it is early in the morning after a long day so I may be missing something more than just sleep.

 

[Adam_151]

Whenever I've needed to do this I've used 100n X2 rated caps from rapid electronics

Its important to get X or X2 rated parts (as the one linked to further up the thread does seem to be)... these are designed to be connected to the mains and are approved for this

http://www.rapidonline.com/sku/Elec...n/NPX-X2-Suppression-capacitors/74987/10-2443