need electrical with a video projector

[VJ AIWAZ]

i have this 15000 ansi video projector and am having trouble powering it
it requires 200-240v 9.7amps 1700w ok having said that i brought it to a club where i work and the club electrician/lighting guy
tried to hook it up with 2 110v lines out of phase and the projector didnt like it at all
so i went out and got a step up transformer and it seemed to work but after a few uses the transformers burn out we have been getting about 50hrs per stepup then they don't work
so at my last show i went through 2 of them in like 5 hrs so i opened them up to find that the wires to the fuse holder came unsolderd from heat but the fuse didn't blow

so i have spent over $700 on burnt out step up's


below is the spec from the manual

This projector uses nominal input voltages of 200–240 V AC. It
is designed to work with single-phase power systems having a
grounded neutral conductor. To reduce the risk of electrical shock,
do not plug into any other type of power system.
If you are not sure of the type of power being supplied, consult
your authorized dealer or service station.
Connect the projector with all peripheral equipment before turning
on the projector.

thanks
--
John
VJ AIWAZ

[Doc]

Something like this with the primary and secondaries reversed shouldn't have any trouble at all.

[Things]

Mount a nice big heatsink on the transformer and a fan, that should keep the heat problem fixed.

[300EVIL]

I have a bunch of very nice 1KVA step-up transformers. I could build you a nice 3KVA unit out of them for you that will handle the surge and operating current. Let me know if you are interested.

[Doc]

I have a bunch of very nice 1KVA step-up transformers. I could build you a nice 3KVA unit out of them for you that will handle the surge and operating current. Let me know if you are interested.

I think 4 or 5KVA would be wiser with a 1700W continuous load. KVA rating is generally the maximum short circuit current multiplied by the open circuit voltage, rather than a true running output power.

[Paul]

KVA rating is generally the maximum short circuit current multiplied by the open circuit voltage, rather than a true running output power.

Hmmm... NOT I hope! The short circuit current of an 1kVA transformer with a nominal secondary voltage of 110V would easily be >50A. In your calculation that would be a >5kVA transformer?
The kVA rating of a transformer is just the max current x output voltage. But since the current can be out of phase with the voltage you can not express it in Watts. (It all depends on the power factor of the load)

[Doc]

Hmmm... NOT I hope! The short circuit current of an 1kVA transformer with a nominal secondary voltage of 110V would easily be >50A. In your calculation that would be a >5kVA transformer?
The kVA rating of a transformer is just the max current x output voltage. But since the current can be out of phase with the voltage you can not express it in Watts. (It all depends on the power factor of the load)

I understand power factor, this guy has already burned out several transformers with this projector (which contains a discharge lamp and probably another transformer for the electronics) lets assume the worse case scenario; power factor of .5/1700W = 3400

So you think it would be foolish to go over spec to a 4KvA transformer?

I would go with 5KvA for comfort.

[Paul]

I understand power factor, this guy has already burned out several transformers with this projector (which contains a discharge lamp and probably another transformer for the electronics) lets assume the worse case scenario; power factor of .5/1700W = 3400

So you think it would be foolish to go over spec to a 4KvA transformer?

I would go with 5KvA for comfort.

My reply was mainly to the statement you made that the VA rating is calculated by the short circuit current x open voltage. That is incorrect. (Bigger transformers have easily short circuit current exceeding 20x nominal!!!)

I am in favor of going about 50% over in VA rating for a resistive load. In this case I would go for about 2.5kVA.
I am writing resistive load since the rating is in Watts. That means that the power factor of the load is (very close to) 1.00. If you have a 2.5kVA transformer, with an average power factor of 0.7-0.8, which is pretty standard, then you will end up with a transformer capable of delivering 2.0kW. I think in general that you should not go over 85-90% of max load on a transformer. This would mean that the 2.5kVA is "just" good enough for the max power consumption of the projector. Cooling air for the transformer is of course essential!

But.... Reading the limited specs of the projector, I would go for a different solution, similar to the solution of the electrician who tried it.
I would connect the projector between two phases. Normally you would get 115Vx1.73 (sq. root of 3) = 199V. (Should be enough...) But before connecting it like this I would check a two things in the projector;

- Is one of the legs connected to the enclosure? If this is the case, remove the connection, but make sure the ground connection is still intact!
- Is there a surge protector installed? If yes, remove it! It will most likely cause a lot of problems and/or explode.

The best thing to do is have this all checked by a qualified electrician.
This way you prevent the problems with the transformer, and the costs involved.

[Doc]

That's the thing with this site, it's impossible to keep things simple


I was close but no cigar.

Snip from a power transformer company's web page:

Transformer Sizing

the secondary is short circuited and the primary voltage is increased to a point at which Z ( in this case 5.75%) of the rated input voltage is reached, then the secondary current is recorded.......

Having checked the data on the transformers that our company uses: Rated 3.3kVA 110V centre tapped earth, maximum continuous duty 1600W

[VJ AIWAZ]

well i have went through at least 5 that were rated at 3000w and 2 that were rated at 5000w the 5000 didnt stop working they just smelled so bad the club thought it was on fire

transformer grease burning smell


these are the 3000w

http://bargainoffers.com/catalog/sev...ter-p-151.html


and 2 that were similar to this bit not this exact model

http://www.estoreoffer.com/ar5000-50...own-p-534.html