which ties in with the increase of stator magnetizing current, under this condition, to increase the gap density and the tangential pull to a large figure. The only way in which the d-c excited rotor could be made to match this performance would be to have its exciting current increase with the angular deflection of the rotor. This is a fundamental difference, arising from a physical characteristic of all permanent magnets.In the second paragraph of the discussion is described an important application of permasyn motors to high-frequency group drives requiring a large number of small motors with an independent high-frequency power supply. The replacement of shadedpole or resistance split-phase motors with permasyns is mentioned. This is a case of the permasyn competing in the nonsynchronous field. Such competition is anticipated in the last sentence of the second paragraph of the paper: "and may be competitive with induction motors on some applications wvhere synchronous speed is desirable but not necessary."There is also a large field of application for group drives of small synchronous motors. There is nothing available for this service in the older designs but the .reluctance motor, which is difficult to prove in, because of its low efficiency and power factor, and its large physical size. D-c excited motors are out of the question, because of the complication of circuits, to provide the d-c, increased maintenance, and probable higher first cost. The permasyn is ideal for synchronous group drives.Such an application has already been made in a new type of drive for nylon pumps. A group of pumps is operated from a single variable frequency motor-generator set, operating over a range of 10 to 60 cycles. The unit pump motors are rated 1/4 hp, 3 phases, 3,600 rpm. Constant torque is maintained over the 600,/3,609-rpm speed range by the linear variation of voltage and frequency. Still lower speeds can be realized if the voltage is raised above the proportional value, below a certain point. About 5,000 of these motors have been sold for this application, and have been in service about 4 years.It is true that the future of the new motor will depend in high degree upon the properties and costs of permanent-magnet materials; and that permanent magnets with considerably higher energy than now available are theoretically possible. It is fair to state that if alnico had not been developed there would be no permasyn.On the other hand, if further improvements are made in magnet materials there will be better permasyns.The output energy of a permanent magnet is determined by multiplying the abscissas of the demagnetization curve in oersteds by the corresponding ordinates in gausses. The energy will thus be zero at the Br and Hc points of intersection of the curve with the Y and X axes, because one of the factors is zero. Then the product will rise as one moves around the curve from the Br to the Hc point, pass a maximum value, and then decrease. Thus, referring to the Alnico V curve in Fig. 6, if we had plotted an energy curv...
