Followspot Ballasts

[Ollie]

Just a quick one, what is the difference, advantages and disadvantages, between electronic and magnetic ballasts for discharge sources?

 

Cheers

 

Ollie

[AndrewR]

I'm not an electronics engineer so I apologise if I fluff this:

 

IIRC (from my time at the Followspot Dept at what was VLPS) They are essentially the same, its just that the electronic ones boost the frequency (and possibly the voltage) being supplied to the actual transformer. This boosts the efficiency, and allows you to use a much smaller and lighter coil. So providing its good quality the electronic one is better, as you dont need as much effort to lift it ;) but there are more things to go wrong.... It will also be less likely to produce a nasty transformer hum, one you can hear anyway.

[dbuckley]

That description is close enough for rock and roll ;)

 

Other thing handy about electronic ballasts is that they'll generally run on multiple voltages, and often will autosense what they're plugged into, so you can take your discharge stuff on a world tour without fretting. An electronic discharge "ballast" is really a switched mode power supply, just like the technology used in the humble PC.

[boac]

could anyone put some numbers to this? ie the frequency (and possibly voltage) would be boosted to what level?

[dbuckley]

Frequency will be tens of KHz. Voltage isn't actually boosted, its dropped, discharge lamps usually run on < 100V, which is how you can run them off 110V mains using conventional magnetic ballasts.

 

The only voltage boost is for the ignitor, which is a pulse of several thousand volts(!) to get the discharge going. But thats the same with both types of ballast.