Staco VARIAC 1010, 1020, 1210, 1220 Series Variable Staco VARIAC Variable Transformer 1000 and 1200 Series. The 1020B variable transformer coil operates on 120 or 240 volts and has a constant current rating of up to 3.5 amperes. Both variable transformer types include coil tapping arrangements allow for 0 to input line voltage or 17% above line voltage. The 1020 taps allow the unit to double the input voltage if desired. Staco VARIAC Variable Transformer 2510 and 2520 Series Staco VARIAC Variable Transformer 2510 and 2520 Series The 2510/2520 Series Variable Transformers represent a compact high current variable transformer design. The 2510, 120 volt variable transformer coil is rated at 25 amperes for constant current loads; while the 2520, 240 volt variable transformer coil is rated at 10 amperes for constant current loads.