The Maximum Current can only be drawn in line-voltage connection with the listed (or lower) input voltage across the whole "Dimmer Dot" winding (e.g. 240 volts on a 240/270 volt unit), and can only be drawn near zero or at or near full output voltage. A load having linear voltage/current load, line (constant impedance load drawing maximum current at the line voltage can be controlled from zero to line voltage. The knowledge of the maximum current and the rated current for the particular end application can be useful for filling in the capacity gap for the "Dimmer Dots" in the range and thus intermediate current requirements can at time be met from the particular rating valued "Dimmer Dots". KVA RATINGS
Equals nominal input voltage multiplied by maximum current output. KVA rating for over voltage connection, equals output voltage multiplied by rated current.
OVER VOLTAGE CONNECTIONS:
A "Dimmer Dot" transformer connected for over voltage provides an output of 12 % above the supply voltage on load. Most models have terminations for line voltage or over voltage connection, at the option of the user. Rated' current only may be drawn when over voltage connected.
Although 'Dimmer Dot" are designed for arduous industrial use, damage will occur if they are subjected to short circuit or continuous severe overload.
It is therefore recommended that protective devices be fitted such as a circuit breaker in the input circuit & and H.R.C. fuse in the load circuit. It is normal practice to provide a protective device in the in>put circuit.
It is not always appreciated that a variable transformer with an input voltage of 250 V and delivering say 10 amps to a load at 50 V (0.5 KVA), will draw a current of only 2 amps from the supply mains. It this instance, a 10 amp. fuse laced in the input circuit would not rupture until the load current reached 50 amps . It is obvious, therefore, that input protective device afford little protection to the transformer against overloads at low output voltage. The solution is, of course, to fuse the load circuit with an H.R.C. fuse link.