Question for the electrically gifted...

Smoke Eater · 13th June 2003, 08:23 PM

I'm interested in operating a 36volt 400 watt bulb off of a 120vac household current source. Is a transformer necessary, or can the voltage reduction be made by a wire-wound rheostat (or pot?)? Is there a better way? In the end, I need about 11-12 amps of 36 volt power to the bulb. Any help or guidance would be appreciated. Thanks, Smoke Eater

SY · 13th June 2003, 08:26 PM

If you don't mind wasting an enormous amount of power and generating kilowatts of heat, a resistor will work. A transformer might be a bit more sensible.

Smoke Eater · 13th June 2003, 08:30 PM

Thanks, SY, I just seem to have trouble finding a transformer that takes 120vac and outputs 36 with at least 11 amps. Either I'm not searching for it correctly or they don't make many. Is an 11 amp output asking a lot of a transformer? Or should I be looking for some other "factor" that would help me properly size it?

Christer · 13th June 2003, 08:38 PM

I don't think there should be much of a problem to find such
a transformer. A 400VA should do the job. Just as a sample
I cheked Plitron and they have a 400VA toroid with 35V
secondary. I suppose that would be close enough for your
purposes.

Smoke Eater · 13th June 2003, 09:15 PM

Thanks Christer, I'll start searching by "400va" and see if I can turn up any that have 35-36 volt secondary. I'm just looking for an inexpensive way to upgrade from a 24volt 275watt halogen bulb to a 36volt 400w bulb.

Question for SY (and anyone else), Is the heat generated by the resistance of the rheostat greater than what would be generated by a transformer? I guess what I'm asking is, are transformers more capable of dealing with the heat, or do they not create as much heat as a rheostat? (I always thought that a transformer worked similar to a rheostat, just using more windings and not adjustable

) Thanks for you help, Smoke Eater

SY · 13th June 2003, 09:24 PM

Enormously greater heat from the resistor. At 11-12 amps, you'll be radiating a kilowatt from that poor little thing. A transformer will only have a few percent loss, adding up to a few watts.

Smoke Eater · 13th June 2003, 09:41 PM

Thanks for all your help, I found the Plitron site and located the transformer that Christer had mentioned. Sounds like just what I need. (Also stumbled across a "wind your own transformers" website...egads!) Thanks again to both of you, Take Care, Smoke Eater

Christer · 13th June 2003, 09:53 PM

I won't hurt to look around a bit for other brands. I have no
idea if Plitron are cheap or expensive, I just checked their
site since I know many of you in the US buy their stuff.

13th June 2003, 08:23 PM	#1
Smoke Eater diyAudio Member Join Date: Sep 2002 Location: Missouri	Question for the electrically gifted... I'm interested in operating a 36volt 400 watt bulb off of a 120vac household current source. Is a transformer necessary, or can the voltage reduction be made by a wire-wound rheostat (or pot?)? Is there a better way? In the end, I need about 11-12 amps of 36 volt power to the bulb. Any help or guidance would be appreciated. Thanks, Smoke Eater

13th June 2003, 08:26 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	If you don't mind wasting an enormous amount of power and generating kilowatts of heat, a resistor will work. A transformer might be a bit more sensible. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

13th June 2003, 09:24 PM	#6
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Enormously greater heat from the resistor. At 11-12 amps, you'll be radiating a kilowatt from that poor little thing. A transformer will only have a few percent loss, adding up to a few watts. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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13th June 2003, 08:30 PM	#3
Smoke Eater diyAudio Member Join Date: Sep 2002 Location: Missouri	Thanks, SY, I just seem to have trouble finding a transformer that takes 120vac and outputs 36 with at least 11 amps. Either I'm not searching for it correctly or they don't make many. Is an 11 amp output asking a lot of a transformer? Or should I be looking for some other "factor" that would help me properly size it?

13th June 2003, 08:38 PM	#4
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	I don't think there should be much of a problem to find such a transformer. A 400VA should do the job. Just as a sample I cheked Plitron and they have a 400VA toroid with 35V secondary. I suppose that would be close enough for your purposes.

13th June 2003, 09:15 PM	#5
Smoke Eater diyAudio Member Join Date: Sep 2002 Location: Missouri	Thanks Christer, I'll start searching by "400va" and see if I can turn up any that have 35-36 volt secondary. I'm just looking for an inexpensive way to upgrade from a 24volt 275watt halogen bulb to a 36volt 400w bulb. Question for SY (and anyone else), Is the heat generated by the resistance of the rheostat greater than what would be generated by a transformer? I guess what I'm asking is, are transformers more capable of dealing with the heat, or do they not create as much heat as a rheostat? (I always thought that a transformer worked similar to a rheostat, just using more windings and not adjustable ) Thanks for you help, Smoke Eater

13th June 2003, 09:41 PM	#7
Smoke Eater diyAudio Member Join Date: Sep 2002 Location: Missouri	Thanks for all your help, I found the Plitron site and located the transformer that Christer had mentioned. Sounds like just what I need. (Also stumbled across a "wind your own transformers" website...egads!) Thanks again to both of you, Take Care, Smoke Eater

13th June 2003, 09:53 PM	#8
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	I won't hurt to look around a bit for other brands. I have no idea if Plitron are cheap or expensive, I just checked their site since I know many of you in the US buy their stuff.

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