Moving Picture World (Nov-Dec 1927)

November 5, 1927 MOVING PICTURE WORLD 51 a Another Hertner business M aker HE Hertner Electric Company has announced a new Transverter, to be known as the “Type C. P. Transverter.” The distinct feature of these Transverters is the voltage regulation of the generators. The voltage of the usual commercial ; type of generator will de( crease from ten per cent. ) to fifteen per cent, when operated with a fixed field regulator over a period of time sufficient for the windings to reach a constant temperature. This means that in order S to obtain satisfactory results with the projection equipment, the projectionist must manipulate the field regulator : as the generator warms up so as to maintain a constant bus voltage. The Type C. P. Transverters are designed to deliver within > two and one-half per cent, of the rated voltage under all conditions of temperature and loads (within the rating of the generator). This feature makes it possible for the projectionist to operate the Transverter during the entire show without manipulating the field regulator. As an example the hot and cold volt ampere performance curves of the type C. P. 300 ampere 100 volt Transverter show the small decrease in voltage of the generator as it heats up. These Transverters are rated on a projection room duty basis. The Power Club rating for 40° C. machines is that no part of the machine shall have a temperature rise above the room temperature of more than 40° C. when operated : continuously at full load, except the commutator which may have a rise of 50° C. When operated at twenty-five per cent, overload for two hours the temperature rise of the windings should not exceed 55° C. and the commutator 70° C. The projection room duty rating which we have adopted for Type C. P. Transverters is the same as the I Power Club rating for continuous duty, but is on a basis of fifty per cent, overload for thirty minutes. This latter rating', we feel, is very much more adapted to projection room conditions, as there will probably never be an occasion to operate at an overload for more than thirty minutes in any two-hour period. The Type C. P. Transverters are built in the four oilbearing type consisting of a squirrel cage induction motor specially designed for motor generator service directly connected by means of a flexible coupling to the generator. ! The two units are mounted on a substantial cast iron base. The generator is particularly well ventilated, provisions being made to draw air in through the commutator core and also through the rear end of the armature, and discharge it about the field coils. The entire generator is designed with the idea of keeping the voltage variation down to a minimum. This has made it desirable to build the generator as open as possible, so as to permit maximum ventilation. The frames are relatively large as compared to the size of frame usually used with a given diameter armature. Sufficient room for the shunt field winding is secured in this way. The most advanced methods are used in the construction of these machines. The best of materials is used. The various parts are machined to a precision beyond usual practice. The shafts are of medium carbon steel and ground to a high finish. The rotating parts are balanced dynamically on a Gisholt balancing machine, which produces results of the highest accuracy. The Type C. P. Transverters have been designed to deliver 100 volt direct current. It seems to be the consensus of opinion that a D. C. bus voltage of 100 volts is desirable where high intensity lamps are used. However, they can be furnished to deliver 85 or 90 volts direct current if so ordered. The very close voltage regulation will only be obtained when operating at the rated voltage. The list prices of the Type C. P. Transverters with motors for two or three phase, sixty cycle, 220, 440 or 550 volts are as follows: Continuous 30 Minute D. C. List List Motor Ampere Ampere Volts Price Price H. P. Capacity Capacity M. G. set and M. G. set Field Regulator and Panel A 150 225 100 $1550 $1660 24 200 300 100 1820 1930 30 250 375 100 2060 2180 40 300 450 100 2300 2420 50 400 600 100 2750 2900 60 500 750 100 3200 3350 75 600 900 100 3630 3780 90 750 1125 100 4250 4400 115 The prices of these outfits are higher than the type M. A. (Please turn to page 58) This department is exclusively for Better Business Builders. Therefore, when you see herein an announcement and description of new apparatus that has a bearing on business building, you may take it for granted that the staff of this department considers the admitted apparatus as living up to that qualification. Comment or criticism of such devices will appear in F. H. Richardson’s Better Projection department at another time.