132:
A shaft grounding ring is installed around the motor shaft and creates a low impedance pathway for current to flow back to the motor frame and to ground. Various styles of rings exist such as those containing microfilaments making direct contact with the shaft or rings that clamp onto the shaft with
123:
Grounding the shaft by installing a grounding brush device on either the non-drive end or drive end of a VFD electric motor provides an alternate low-impedance path from the motor shaft to the motor case. This method channels the current away from the bearings. It significantly reduces shaft voltage
141:
Insulated bearings eliminate the path to ground through the bearing for current to flow. However, installing insulated bearings does not eliminate the shaft voltage, which will still find the lowest impedance path to ground. This can potentially cause a problem if the path happens to be through the
49:
systems. DC machines may have leakage current from the armature windings that energizes the shaft. Currents due to shaft voltage causes deterioration of motor bearings, but can be prevented with a grounding brush on the shaft, grounding of the motor frame, insulation of the bearing supports, or
53:
Shaft voltage can be induced by non-symmetrical magnetic fields of the motor (or generator) itself. External sources of shaft voltage include other coupled machines, and electrostatic charging due to rubber belts rubbing on drive pulleys.
69:, so the coupling is often weak at 50–60 Hz line frequency. But many Variable Frequency Drives (VFD) induce significant voltage onto the shaft of the driven motor, because of the kilohertz switching of the
340:
284:
Busse, D.F.; Erdman, J.M.; Kerkman, R.J.; Schlegel, D.W.; Skibinski, G.L. (1997). "An evaluation of the electrostatic shielded induction motor: A solution for rotor shaft voltage buildup and bearing current".
111:
An electrostatic shielded induction motor (ESIM) is one approach to the shaft-voltage problem, as the insulation reduces voltage levels below the dielectric breakdown. This effectively stops
366:
A Unique System for
Reducing High Frequency Stray Noise and Transient Common Mode Ground Currents to Zero, While Enhancing Other Ground Issues Meeting Notices and Rule Changes
347:
233:
243:
312:
115:
degradation and offers one solution to accelerated bearing wear caused by fluting, induced by pulsewidth modulated (PWM) inverters.
70:
37:
and generators due to leakage, induction, or capacitive coupling with the windings of the motor. It can occur in motors powered by
201:
213:"Turning The Tables On Shaft Voltage And Bearing Currents", David W. Schlegel, Russel J. Kerkman, and Gary L. Skibinski,
81:. The presence of high frequency ground currents can cause sparks, arcing and electrical shocks and can damage bearings.
396:
391:
381:
38:
386:
74:
401:
62:
156:
High frequency grounding can be significantly improved by installing shielded cable with an extremely
157:
112:
94:
58:
24:
197:
294:
89:
Techniques used to minimise this problem include: insulation, alternate discharge paths,
218:
151:
90:
34:
375:
173:
46:
160:
path between the VFD and the motor. One popular cable type is continuous corrugated
106:
365:
124:
and therefore bearing current by not allowing voltage to build up on the rotor.
66:
20:
271:
161:
78:
255:
298:
341:"Technical guide No. 5 – Bearing currents in modern AC drive systems"
42:
133:
a carbon brush riding on the ring (not directly on the shaft).
215:
61:
to the motor's electrical windings, but the effective
19:"Zero-ground" redirects here. Not to be confused with
244:
Shaft grounding. A solution to motor bearing currents
272:Are Bearing Currents Causing Your Motor Failures?
228:"How to Select a VFD", John Yoon (PE, LEED AP),
267:
265:
368:from Electrical Manufacturing and Coil Winding
142:driven load or through some other component.
97:, grounding brush and shaft grounding ring.
8:
16:Phenomenon in electric motors and generators
287:IEEE Transactions on Industry Applications
23:. For zero voltage ground or neutral, see
185:
43:heating, ventilation, air conditioning
7:
71:insulated gate bipolar transistors
14:
192:Hamid A. Toliyat, G. B. Kliman
57:Every rotor has some degree of
230:Consulting-Specifying Engineer
93:, insulated bearings, ceramic
1:
194:Handbook of electric motors
73:(IGBTs), which produce the
418:
149:
104:
18:
313:"Shaft Grounding Systems"
39:variable-frequency drives
75:pulse-width modulation
256:"Control Engineering"
128:Shaft grounding ring
77:used to control the
59:capacitive coupling
41:, as often used in
137:Insulated bearings
25:Ground and neutral
397:Electrical wiring
392:Electrical safety
299:10.1109/28.649969
232:, November 2010,
409:
362:
360:
358:
353:on July 20, 2011
352:
346:. Archived from
345:
327:
326:
324:
322:
317:
309:
303:
302:
293:(6): 1563–1570.
281:
275:
269:
260:
259:
252:
246:
241:
235:
226:
220:
211:
205:
196:CRC Press, 2004
190:
85:Counter-measures
67:high-pass filter
63:inline capacitor
417:
416:
412:
411:
410:
408:
407:
406:
382:Electric motors
372:
371:
356:
354:
350:
343:
339:
336:
331:
330:
320:
318:
315:
311:
310:
306:
283:
282:
278:
270:
263:
254:
253:
249:
242:
238:
227:
223:
212:
208:
191:
187:
182:
170:
154:
148:
139:
130:
121:
119:Grounding brush
109:
103:
87:
35:electric motors
28:
17:
12:
11:
5:
415:
413:
405:
404:
399:
394:
389:
387:Electric power
384:
374:
373:
370:
369:
363:
335:
334:External links
332:
329:
328:
304:
276:
261:
247:
236:
221:
206:
184:
183:
181:
178:
177:
176:
169:
166:
164:sheath cable.
152:Shielded cable
150:Main article:
147:
146:Shielded cable
144:
138:
135:
129:
126:
120:
117:
105:Main article:
102:
101:Faraday shield
99:
91:Faraday shield
86:
83:
15:
13:
10:
9:
6:
4:
3:
2:
414:
403:
400:
398:
395:
393:
390:
388:
385:
383:
380:
379:
377:
367:
364:
349:
342:
338:
337:
333:
314:
308:
305:
300:
296:
292:
288:
280:
277:
273:
268:
266:
262:
257:
251:
248:
245:
240:
237:
234:
231:
225:
222:
219:
217:, June 1998,
216:
210:
207:
203:
199:
195:
189:
186:
179:
175:
174:Stray voltage
172:
171:
167:
165:
163:
159:
158:low impedance
153:
145:
143:
136:
134:
127:
125:
118:
116:
114:
108:
100:
98:
96:
92:
84:
82:
80:
76:
72:
68:
64:
60:
55:
51:
48:
47:refrigeration
44:
40:
36:
32:
31:Shaft voltage
26:
22:
402:Power cables
355:. Retrieved
348:the original
319:. Retrieved
307:
290:
286:
279:
250:
239:
229:
224:
214:
209:
204:, pp.672-688
193:
188:
155:
140:
131:
122:
110:
107:Faraday cage
88:
56:
52:
30:
29:
50:shielding.
21:ground zero
376:Categories
202:0824741056
180:References
65:acts as a
33:occurs in
274:Greenheck
321:30 March
168:See also
162:aluminum
95:bearings
357:May 23,
113:bearing
200:
351:(PDF)
344:(PDF)
316:(PDF)
79:motor
359:2011
323:2023
198:ISBN
45:and
295:doi
378::
291:33
289:.
264:^
361:.
325:.
301:.
297::
258:.
27:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.