A new concentric standard dynamometer wattmeter for heavy currents: and concentric non-inductive standards of low resistance

Causes of defects in heavy-current dynamometer wattmeters. Concentric main-current coils. Progress of construction of experimental current coils, and their defects. Pressure coils for use with concentric current coils. Comparative tests between concentric and Duddell-Mather wattmeters. Calibration of reflecting concentric standard. Wattmeters for high, and for low power-factor measurements. Double-element wattmeters for two-phase and three-phase power measurements. Advantages of concentric construction. Use of reflecting concentric instrument as a standard ammeter for alternating currents. Construction of concentric non-inductive standards of low resistance. Measurement of the phase errors in current transformers, and in the series coils of dynamometer wattmeters. Appendix. Calculations relating to different shapes of pressure coils for concentric wattmeters.