Electronics in heavy engineering

For years after the thermionic valve had been brought to a high state of perfection, and had been the means of achieving literally amazing results in very low-current circuits, neither its designers nor power engineers realized that it was capable of rendering the same services in heavy-current engineering. That realization has now come, and the paper describes the role that electronics has played and can in future play in industry. After considering the fitness of the glass valve to form part of an industrial equipment, the principal functions which valves have performed in radio practice are considered in relation to their application in industry. First the mercury arc rectifier is compared with the mercury-filled rectifying valve, and the new forms are described which have resulted from a combination of the two, with their respective uses in power engineering. Then the enlargement of the oscillator and amplifier stages is similarly treated. Industrial oscillators and H.F. generators, with their applications, are dealt with. Apparatus based upon electronic amplification are next considered. After a short section on industrial A.C. and D.C. amplifying circuits, including magnetic amplifiers, schemes governed by the photo-cell and by vibration and other pickups are described, including very heavy applications, one installed as far back as 1931. The theory of closed-cycle control follows, with methods of stabilization by mechanical and electrical feedback, the use of amplified field-current control and rotary amplifiers leading to the design of servo-mechanisms. Electronic motor control is treated analytically, by listing first the defects of standard contactor gear, and then giving the type of motor required and its characteristics, the general principle of control, the component parts of a control circuit to give effect to these principles, and the building up of a complete scheme. Applications of the cathode ray oscillograph in heavy testing rendered possible by a- mplification include winding comparators, permeability measurement, fault detection and location for electrical machines and batteries, and the use of radiolocation schemes in industry. Finally, a short section is devoted to electronic instruments used in industry (apart from those already mentioned), including metal detection.