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andybuk · Mar 15, 2007, 08:28 AM

Hi,
I'm in the process of repairing a DJ light system with a knackered transformer. It was causing the internal fuses to blow, so I've replaced the transformer, but it's now taken to blowing the bulbs within it. I'm guessing this is due to too high a voltage, or too much current flowing, but I just need to understand exactly what the ratings I have mean.

The transformer is identical to the old one in rating. 240V input to 2 x 24V secondary outputs, in series to create 48V. I've already noticed that this is actually producing 52V with no load attached. The transformer is 300VA, used to power two 150W 24V bulbs, also in series.

When a transformer is rated at 300VA, does that mean, when it's supplying 48V on the secondary, that it will supply 6.25A, or that this is the maximum it can supply? Also, how sensitive are halogen bulbs to a couple of volts difference to the rating? If it would work, I could get hold of higher rated bulbs, but I'm not sure whether to go for the same voltage rating, but a higher wattage, or to go for the same wattage with a higher voltage?

Hope that makes sense

Cheers

Morrowrj · Mar 17, 2007, 03:52 PM

Originally Posted by andybuk

Hi,
I'm in the process of repairing a DJ light system with a knackered transformer. It was causing the internal fuses to blow, so i've replaced the transformer, but it's now taken to blowing the bulbs within it. I'm guessing this is due to too high a voltage, or too much current flowing, but I just need to understand exactly what the ratings I have mean.

The transformer is identical to the old one in rating. 240V input to 2 x 24V secondary outputs, in series to create 48V. I've already noticed that this is actually producing 52V with no load attached. The transformer is 300VA, used to power two 150W 24V bulbs, also in series.

When a transformer is rated at 300VA, does that mean, when it's supplying 48V on the secondary, that it will supply 6.25A, or that this is the maximum it can supply? Also, how sensitive are halogen bulbs to a couple of volts difference to the rating? If it would work, I could get hold of higher rated bulbs, but I'm not sure whether to go for the same voltage rating, but a higher wattage, or to go for the same wattage with a higher voltage?

Hope that makes sense

Cheers

Yes, the 300VA means that the MAX it can produce is 6.25 amps @48 volts. Did you make any other changs to the circuit ?
Also, I would not increase your bulb wattage anymore that the 150watts because you are already at the limit of the transformer. (wattage or power is = to current times voltage) or in your case , 48V x 6.25A = 300 watts
It is possible, depending on the quality of the transformer, that is is going overvoltage in an attempt to provide the necessary current. If this is the case then either a higher VA transformer or higher voltage bulbs may be more suited.

Good Luck,
Morrowrj