International projectionist (Jan-Dec 1935)

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3 INTERNATIONAL PROJECTIONIST Mary 1935 depend on the ratio of primary to secondary turns. The greater the number of turns in the primary the greater will be the step-down, and the lower the voltage generated in Coil 5-6. Switch KS-6204 is obviously intended to put Coils 1-2 and 3-4 in series with each other or in parallel with each other, as desired. When they are in series the number of turns in the primary winding is doubled, and the voltage generated in Coil 5-6 is halved. Just to the right of this switch we see two guide figures — "10 V." and "5 V." These alone tell us that when this switch is in the lower position, Coils 1-2 and 3-4 are in series, a fact easily confirmed by studying the wiring in detail. Having thus far analyzed what this apparatus does and how it does it, we can proceed to trace the circuits step-by-step. Without the foregoing, tracing interlocked circuits in detail would be unproductive of anything but confusion. The line power enters at the upper left, through switch No. 18825 and a pair of 20-amp. fuses, and passes through the cabinet to the load terminals at the upper right. One of the two legs of this line contains Coil 5-6 in series. A wire runs from Point 6 of this coil left about an inch and then down to Point 6 of a single-pole, single-throw switch. The drawing reads: "Shorted in Off Position"; apparently this single-pole switch is part of KS-6203, and closes when KS-6203 is turned to "Off." Reference to Figure 2 shows that Switch KS-6203 does, in fact, contain terminals numbered 5 and 6. Therefore when KS-6203 is turned off, no power is supplied to the transformer, no voltage is generated in Coil 5-6 and that coil is short-circuited. When Switch KS-6203 is in "Off" position the full line voltage flows directly to the load precisely as if this voltage control cabinet did not exist. Circuit for Switches When Switch KS-6203 is placed in "Raise" position to increase the line voltage, the short-circuit is removed from Coil 5-6, which then becomes operative. Two positions are possible for Switch KS-6204. a BeVQNT *78P. re I PL £ POLE 5)Y. expulsion type 20 amp -zso v. Figure 2 Let us assume KS-6204 to be in the 10-volt position. (Both switches are now "Up.") Tracing the circuit from the left-hand side of the supply line, it runs: down, right and down to Point 2 of KS6203. Up through the switch bar to Point 1, diagonally down-left to the other Point 1, and down, right and upward to Point 4 of KS-6204. Here the circuit breaks into two branches: one runs directly through Coil 3-4 of the transformer to Point 3 of the switch, and upward through the switch bar to Point 1 of the switch. The other branch runs upward through the switch bar to Switch Point 2, thence through Coil 1-2 to unite with the other branch at Point 1 of the switch. From this junction the circuit may be traced down and left to Point 4 of KS6203, diagonally up-left to the other Point 4 of that switch, down through the switch bar to Point 3 of KS-6203, and thence upward to the right-hand side of the line. In the circuit, as just traced, the line voltage has been increased by ten volts, the two halves of the transformer primary being in parallel. Now, with KS-6203 up, let us put KS6204 down, in the "5 V." position. Lower Point 1 of KS-6203 is still the left-hand side of the power line. From that point we follow right and up to Point 4 of KS-6204. (This switch is now down.) Thence upward, through Coil 3-4 to &£rh/££H TSieA7/A/Al£> /AHDB !*/*£/</ TA.-4030 ^/LTEJC /S C/S££?. W.L. ZO" TYPE "O" BESISTOg. IV. L. -44' gHEO. Point 3 of KS-6204. From Point 3 downward through the bar of the switch, and thence right-upward to Point 2, through Coil 1-2 and down-right to Lower Point 4 of KS-6203. The two transformer windings are now in series, the number of turns in the primary has been doubled, the secondary voltage is therefore less, and only five volts has been generated in Coil 5-6. In the same way we might put Switch KS-6203 in "Lower" position and trace through both positions of KS-6204, but that would be essentially repeating what has just been done and to no particular advantage. That change merely reverses the polarity of the line. As just traced, the left-hand side of the power line fed into Point 4 of KS-6204. With KS-6203 down, the left-hand side of the power line feeds instead into Point 1 of KS-6204. This control cabinet is capable of five positions: either a 5 or a 10-volt increase in voltage, or a 5 or a 10-volt decrease in voltage, and — fifth positionno change in the line voltage, when KS-6203 is "Off" and Coil 5-6 short-circuited. Figure 2 is the wiring diagram of the same apparatus and shows the physical arrangement and appearance of the component parts. We note that the switches we have just examined are not knife switches but rotary snap switches. We cannot trace their circuits in Figure 2, but since their terminals are numbered in both drawings we can easily understand Figure 2 by reference to Figure 1. One other point of interest about Figure 2 is that the Line and Load terminals are paralleled at both top and bottom of the cabinet, for convenience in connection to a conduit brought in from either above or below. This device, of course, is useful only with a. c, since d. c. will not actuate the transformer. A Simple D.C. Control Circuit A very simple d. c. voltage control circuit is shown in Figure 3, which is a voltage regulating device used with either a 1 10-volt commercial power line, or with the d. c. side of an arc supply generator. It controls the d. c. voltage to loud speaker fields. Very similar circuits are sometimes used to regulate a. c. voltage to amplifiers. The input to Figure 3 can be seen at the left, marked "Line + and ■ — ." This input may be anywhere from 60 to 130 volts, depending on the source. The output to stage horns and monitor is seen at the extreme right. All stage speakers o + 3 nmp. POSES FIGURE 3 toaz/toa? o