nber category 4 Electrical & Electronic subcat 45 Power Systems

uspto classes
60 Power Plants
136 Batteries: Thermoelectric and Photoelectric
290 Prime-Mover Dynamo Plants
310 Electrical Generator or Motor Structure
318 Electricity: Motive Power Systems
320 Electricity: Battery or Capacitor Charging or Discharging
322 Electricity: Single Generator Systems
323 Electricity: Power Supply or Regulation Systems
361 Electricity: Electrical Systems and Devices
363 Electric Power Conversion Systems
388 Electricity: Motor Control Systems
429 Chemistry: Electrical Current Producing Apparatus, Product, and Process

Historic patent counts for subcat 45

uspto search in the 1790 to present database

ccl/60/$ OR ccl/136/$ OR ccl/290/$ OR ccl/310/$ OR ccl/318/$ OR ccl/320/$ OR ccl/322/$ OR ccl/323/$ OR ccl/361/$ OR ccl/363/$ OR ccl/388/$ OR ccl/429/$

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