From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of motor efficiency by comparing electrical and mechanical properties through plotted curves.
| Identifier | WestWitteringFiles\T\2July1929-December1929\ Scan020 | |
| Date | 1st July 1929 guessed | |
| -3- contd. current in the field windings only, but is less in general and approximates/[very] closely to the actually existing back E.M.F. upon which the conversion of electrical to mechanical power depends. For each given running condition of the motor it is instructive to compare e_g with E and T_r with T_s. e_g/E we call the electrical efficiency (though it is really purely a copper efficiency) and T_r/T_s the mechanical efficiency (though really it includes the effect of hysteretic iron losses in the armature core). The product e_g/E x T_r/T_s is the overall efficiency of the motor. These three efficiencies might be plotted on an ampere base, i.e. taking current as the fundamental variable. It has however been found more instructive to plot the several quantities E, e_g, Ø_g, T_s, T_r on an ampere base for the various motors which have been considered. For each motor considered, two sets of curves have been produced viz The usual brake test results on a running or brake torque (T_r) base, and curves of some or all of the five quantities E, e_g, Ø_g, T_s, T_r, on an ampere base. In these curves a comparison of e_g with E at currents of various values gives a good idea of the "electrical efficiency" at varying loads, whilst a similar comparison of T_r with T_s gives a good idea of the "mechanical efficiency", these efficiencies being as described above. | ||