PWR221T-30 Power Resistors Bourns PWR221T-30 Power Resistors feature low inductance, high power rating, and a ceramic backplane. PWR221T-30 Power Resistors are TO-220 style power resistors made using thick film on alumina ceramic technology. Bourns PWR221T-30 Power Resistors are used in current limiting, capacitor discharge, or current measurement circuits in power supplies for telecom and industrial applications.