89:
185:(still available from scientific supply houses), although not intended to, clearly demonstrates this great inefficiency, and seriously misleads students as to how real motors work. These early inefficient designs apparently were based on observing how magnets attracted ferromagnetic materials (such as iron and steel) from some distance away. It took a number of decades in the 19th century for electrical engineers to learn the importance of small air gaps. The Gramme ring, however, has a comparatively small air gap, which enhances its efficiency. (In the top illustration, the large hoop-like piece is the laminated permanent magnet; the Gramme ring is rather hard to see at the base of the hoop.)
260:
300:
two smaller windings on opposite sides of the ring. All modern armatures use this externally wrapped (drum) design, although the windings do not extend fully across the diameter; they are more akin to chords of a circle, in geometrical terms. Neighboring windings overlap, as can be seen in almost any modern motor or generator rotor that has a commutator. In addition, windings are placed into slots with a rounded shape (as seen from the end of the rotor). At the surface of the rotor, the slots are only as wide as needed to permit the insulated wire to pass through them while winding the coils.
292:
272:
242:
208:
194:
304:
173:, carelessly connected the terminals of a Gramme machine to another dynamo which was producing electricity, and its shaft began to spin. The Gramme machine was the first powerful electric motor useful as more than a toy or laboratory curiosity. Today some elements of this design forms the basis of nearly all DC electric motors. Gramme's use of multiple commutator contacts with multiple overlapped coils, and his innovation of using a ring armature, was an improvement on earlier
225:
315:, the ring still proves to be a more efficient design, because in a solid core the field lines concentrate in a thin surface region and minimally penetrate the center. For a very large power-generation armature several feet in diameter, using a hollow ring armature requires far less metal and is lighter than a solid core drum armature. The hollow center of the ring also provides a path for ventilation and cooling in high power applications.
330:
20:
593:
299:
Eventually it was found to be more efficient to wrap a single loop of wire across the exterior of the ring and simply not have any part of the loop pass through the interior. This also reduces construction complexity since one large winding spanning the width of the ring is able to take the place of
79:
in 1871. Although popular in 19th century electrical machines, the Gramme winding principle is no longer used since it makes inefficient use of the conductors. The portion of the winding on the interior of the ring cuts no flux and does not contribute to energy conversion in the machine. The winding
287:
Initial attempts to insert a stationary field coil within the center of the ring to help the lines penetrate into the center proved too complex to engineer. Further, if the lines did penetrate the interior of the ring any e.m.f. produced would have opposed the e.m.f. from the outside of the ring
267:
While the Gramme ring permitted a more steady power output, it suffered from a technical design inefficiency due to how magnetic lines of force pass through a ring armature. The field lines tend to concentrate within and follow the surface metal of the ring to the other side, with relatively few
203:
This illustration shows a simplified one-pole, one-coil Gramme ring and a graph of the current produced as the ring spins one revolution. While no actual device uses this exact design, this diagram is a building block to better understand the next illustrations.
180:
Earlier designs of electric motors were notoriously inefficient because they had large, or very large, air gaps throughout much of the rotation of their rotors. Long air gaps create weak forces, resulting in low torque. A device called the
279:
Consequently, the interior windings of each small coil are minimally effective at producing power because they cut very few lines of force compared with the windings on the exterior of the ring. The interior windings are effectively
458:
Hawkins
Electrical Guide Number One, Questions, Answers & Illustrations: a Progressive Course of Study for Engineers, Electricians, Students and those Desiring to Acquire a Working Knowledge of Electricity and its
318:
In small armatures a solid drum is often used simply for ease of construction, since the core can be easily formed from a stack of stamped metal disks keyed to lock into a slot on the shaft.
221:
with the first. Because the bottom coil is oriented opposite of the top coil, but both are immersed in the same magnetic field, the current forms a ring across the brush terminals.
134:
within a static magnetic field, creating brief spikes or pulses of DC resulting in a transient output of low average power, rather than a constant output of high average power.
182:
288:
because the wire on the inside was orientated in the opposite direction to that on the outside having turned through 180 degrees as it was wound.
234:
A two-pole, four-coil Gramme ring. The coils of A and A' sum together, as do the coils of B and B', producing two pulses of power 90° out of
251:
A three-pole, six-coil Gramme ring, and a graph of the combined three poles, each 120° out of phase from the other and summing together.
137:
With more than a few coils on the Gramme ring armature, the resulting voltage waveform is practically constant, thus producing a near
423:
456:
263:
Diagram of magnetic lines through a Gramme ring, showing the very few magnetic lines of force crossing the center gap.
97:
63:. It was the first generator to produce power on a commercial scale for industry. Inspired by a machine invented by
597:
88:
80:
requires twice the number of turns and twice the number of commutator bars as an equivalent drum-wound armature.
618:
623:
435:
295:
Example of a single winding around the exterior of a drum core with no wires penetrating the interior.
259:
130:
machines passed a magnet near the poles of one or two electromagnets, or rotated coils wound on
238:
with each other. When coils A and A' are at maximum output, coils B and B' are at zero output.
217:
A one-pole, two-coil Gramme ring. The second coil on the opposite side of the ring is wired in
369:
108:
291:
174:
146:
123:
in two of the coils on opposite sides of the armature, which is picked off by the brushes.
100:
44:
107:. The coils are connected in series, and the junction between each pair is connected to a
8:
72:
67:
in 1860, Gramme was the developer of a new induced rotor in form of a wire-wrapped ring (
56:
399:
344:
275:
Early form of the Gramme ring armature with coils penetrating the interior of the ring.
170:
161:
in 1873, Gramme accidentally discovered that this device, if supplied with a constant-
119:
which rotates around through the coils in order as the armature turns. This induces a
419:
131:
64:
271:
452:
364:
218:
127:
52:
241:
207:
193:
349:
307:
Modern design of the Gramme ring, wrapped only around the exterior of the core.
166:
138:
116:
48:
612:
335:
311:
While the hollow ring could now be replaced with a solid cylindrical core or
235:
142:
303:
603:
374:
359:
224:
402:
Dynamo-electric machinery: a manual for students of electrotechnics
177:
and helped usher in development of large-scale electrical devices.
329:
162:
120:
60:
19:
592:
379:
354:
158:
112:
284:
and only add resistance to the circuit, lowering efficiency.
76:
439:
104:
462:. New York: Theo. Audel & Co. p. 174, figure 182.
268:
lines of force penetrating into the interior of the ring.
96:
The Gramme machine used a ring armature, with a series of
157:
During a demonstration at an industrial exposition in
442:. Encyclopædia Britannica, Inc. Retrieved 2010-01-11.
418:, Fifteenth Edition. McGraw Hill. Section 8, page 5.
152:
325:
16:Electrical generator that produces direct current
610:
475:
473:
471:
469:
145:producing the magnetic field to become a modern
569:
466:
414:Fink, Donald G. and H. Wayne Beaty (2007),
416:Standard Handbook for Electrical Engineers
115:magnetize the soft iron ring, producing a
188:
71:) and demonstrated this apparatus to the
302:
290:
270:
258:
240:
223:
206:
192:
141:supply. This type of machine needs only
103:, wound around a revolving ring of soft
87:
18:
575:
563:
551:
539:
527:
515:
503:
491:
479:
451:
611:
405:. London: E. & F.N. Spon. p. 140.
111:on which two brushes run. Permanent
23:A Gramme machine or Gramme magneto.
13:
153:Invention of modern electric motor
51:, named for its Belgian inventor,
14:
635:
585:
246:Three-pole, six-coil Gramme ring.
604:Electricity museum: early motors
591:
328:
254:
229:Two-pole, four-coil Gramme ring.
557:
545:
533:
212:One-pole, two-coil Gramme ring.
198:One-pole, one-coil Gramme ring.
521:
509:
497:
485:
445:
429:
408:
400:Thompson, Sylvanus P. (1888),
393:
83:
1:
386:
165:power supply, will act as an
55:, and was built as either a
7:
321:
10:
640:
566:, p. 224, figure 249.
554:, p. 226, figure 251.
542:, p. 223, figure 248.
530:, p. 225, figure 250.
518:, p. 174, figure 185.
506:, p. 174, figure 184.
494:, p. 174, figure 183.
308:
296:
276:
264:
248:
231:
214:
200:
189:Principle of operation
93:
24:
619:Electrical generators
370:Excitation (magnetic)
306:
294:
274:
262:
244:
227:
210:
196:
91:
22:
600:at Wikimedia Commons
436:"Hippolyte Fontaine"
169:. Gramme's partner,
45:electrical generator
578:, pp. 224–226.
482:, pp. 174–178.
73:Academy of Sciences
624:Belgian inventions
345:Electric generator
309:
297:
277:
265:
249:
232:
215:
201:
171:Hippolyte Fontaine
132:double-T armatures
94:
25:
596:Media related to
453:Hawkins, Nehemiah
440:Britannica Online
424:978-0-07-144146-9
65:Antonio Pacinotti
631:
595:
579:
573:
567:
561:
555:
549:
543:
537:
531:
525:
519:
513:
507:
501:
495:
489:
483:
477:
464:
463:
449:
443:
433:
427:
412:
406:
397:
365:Rotary converter
338:
333:
332:
639:
638:
634:
633:
632:
630:
629:
628:
609:
608:
588:
583:
582:
574:
570:
562:
558:
550:
546:
538:
534:
526:
522:
514:
510:
502:
498:
490:
486:
478:
467:
450:
446:
434:
430:
413:
409:
398:
394:
389:
384:
334:
327:
324:
257:
191:
183:St. Louis motor
155:
128:electromagnetic
86:
17:
12:
11:
5:
637:
627:
626:
621:
607:
606:
601:
598:Gramme machine
587:
586:External links
584:
581:
580:
568:
556:
544:
532:
520:
508:
496:
484:
465:
444:
428:
407:
391:
390:
388:
385:
383:
382:
377:
372:
367:
362:
357:
352:
350:Electric motor
347:
341:
340:
339:
323:
320:
256:
253:
190:
187:
167:electric motor
154:
151:
143:electromagnets
139:direct current
117:magnetic field
92:Gramme machine
85:
82:
49:direct current
47:that produces
37:Gramme magneto
29:Gramme machine
15:
9:
6:
4:
3:
2:
636:
625:
622:
620:
617:
616:
614:
605:
602:
599:
594:
590:
589:
577:
572:
565:
560:
553:
548:
541:
536:
529:
524:
517:
512:
505:
500:
493:
488:
481:
476:
474:
472:
470:
461:
460:
454:
448:
441:
437:
432:
425:
421:
417:
411:
404:
403:
396:
392:
381:
378:
376:
373:
371:
368:
366:
363:
361:
358:
356:
353:
351:
348:
346:
343:
342:
337:
336:Energy portal
331:
326:
319:
316:
314:
305:
301:
293:
289:
285:
283:
273:
269:
261:
255:Drum windings
252:
247:
243:
239:
237:
230:
226:
222:
220:
213:
209:
205:
199:
195:
186:
184:
178:
176:
172:
168:
164:
160:
150:
148:
144:
140:
135:
133:
129:
124:
122:
118:
114:
110:
106:
102:
99:
90:
81:
78:
74:
70:
66:
62:
58:
54:
53:ZĂ©nobe Gramme
50:
46:
42:
41:Gramme dynamo
38:
34:
30:
21:
576:Hawkins 1917
571:
564:Hawkins 1917
559:
552:Hawkins 1917
547:
540:Hawkins 1917
535:
528:Hawkins 1917
523:
516:Hawkins 1917
511:
504:Hawkins 1917
499:
492:Hawkins 1917
487:
480:Hawkins 1917
459:Applications
457:
447:
431:
415:
410:
401:
395:
317:
312:
310:
298:
286:
281:
278:
266:
250:
245:
233:
228:
216:
211:
202:
197:
179:
156:
136:
125:
95:
68:
40:
36:
32:
28:
26:
84:Description
69:Gramme ring
33:Gramme ring
613:Categories
387:References
375:Field coil
360:Alternator
109:commutator
282:dead wire
147:generator
455:(1917).
322:See also
219:parallel
126:Earlier
98:armature
175:dynamos
163:voltage
121:voltage
113:magnets
61:magneto
422:
380:Stator
355:Dynamo
159:Vienna
57:dynamo
43:is an
236:phase
101:coils
77:Paris
59:or a
39:, or
420:ISBN
313:drum
105:iron
75:in
615::
468:^
438:,
149:.
35:,
31:,
27:A
426:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.