Ans. Similar to that of an alternator with either delta or Y connections.
Figs. 2,037 to 2,041 show various converter connections between the collector rings and commutator.
Fig. 2,037 indicates how the armature is tapped for two phase connections.
Fig. 2,038 shows three phase delta connections, and fig. 2,039 the three phase Y or star connections.
Six phase delta and Y connections are frequently used as shown in fig. 2,040 and fig. 2,041, both of which require two secondary coils in the transformer, one set of which is reversed, so as to supply the current in the proper direction.
Ques. With respect to the wave, what is the relation between the direct and alternating pressures?
Ans. The direct current voltage will be equal to the crest of the pressure wave while the alternating voltage will depend on the virtual value of the maximum voltage of the wave according to the connections employed.
| DIRECT CURRENT | SINGLE PHASE | TWO PHASE | THREE PHASE | SIX PHASE | TWELVE PHASE | n PHASE | |
|---|---|---|---|---|---|---|---|
| VOLTS BETWEEN COLLECTOR RING AND NEUTRAL POINT | 1 | 1 / (2√2) = .354 | 1 / (2√2) = .354 | 1 / (2√2) = .354 | 1 / (2√2) = .354 | 1 / (2√2) = .354 | 1 / (2√2) = .354 |
| VOLTS BETWEEN ADJACENT COLLECTOR RINGS | 1 | 1 / √2 = .707 | ½ = .5 | √3 / (2√2) = .612 | 1 / (2√2) = .354 | .183 | (SIN(π / n)) / √2 |
| AMPERES PER LINE | 1 | √2 = 1.414 | 1 / √2 = .707 | (2√2) / 3 = .943 | √2 / 3 = .472 | .236 | (2√2) / n |
| AMPERES BETWEEN ADJACENT LINES | 1 | √2 = 1.414 | ½ = .5 | (2√2) / (3√3) = .545 | √2 / 3 = .472 | .455 | (√2SIN(π / n)) / n |
In a single phase rotary, the value of the direct pressure is 1 to .707, therefore a rotary which must supply 600 volts direct current must be supplied by 600 × .707 = 424 volts alternating current. For three phase rotaries the ratio is 1 to .612, or in order to produce 600 volts direct current, 600 × .612 = 367 volts on the alternating current side of the rotary is required.
