Technical Paper
Development of 200 Ampere Regulated Transformer Rectifier
1999-04-06
1999-01-1365
Historically, Transformer Rectifiers Units (TRUs) have been unregulated devices used to provide 28-Volt Direct Current (vdc) power on 400 Hertz, 115-Volt Alternating Current (vac) aircraft. By design, a TRU produces an unregulated voltage output that varies with current (load) required by utilization equipment on the 28-Volt Buss. This TRU voltage output variation typically ranges from 30-31 volts (at no load) down to 24 volts (at 100%load) under stable input conditions. AC transients, in combination with sudden or heavy DC loads, can cause a typical TRU voltage output to fall into the 17-18 volt range or even lower. Modern aircraft are experiencing three trends which are impacted by older TRU characteristics. The first is that airframes are being used for longer periods of time; scheduled use is being increased to avoid the budget constraints of replacing costly airframes.
