Would 75 watt rated control gear work a 30 watt tube, and only use 30 watts of power ?
i.e. can I interchange the control gear from fluorescent fittings providing the control gear is rated higher than the tube it will operate.
Generally, no.
There are cases where this works. The shorter tubes in the same family, such as the 4, 6, 8, 13W tubes can run from the same control gear because they all run at the same tube current and their voltage drop is small compared with the mains voltage so the variation in voltage across the ballast is small enough that the tube current doesn't change much from one end to the other end of the range. The other case is electronic control gear which will often drive a number of different tubes with the same current specification because they provide a constant current source to the tube.
No. Some chokes will list more than one possible tube rating, but otherwise no.
NT
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