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Q: AC Power Supply: 50 Hz or 60 Hz? ( Answered ,   7 Comments )
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 Subject: AC Power Supply: 50 Hz or 60 Hz? Category: Science Asked by: probonopublico-ga List Price: \$5.00 Posted: 19 Nov 2002 12:14 PST Expires: 19 Dec 2002 12:14 PST Question ID: 110766
 ```I believe that it was Tesla who decided that 60 Hz was the right frequency for AC power distribution in the US and that, later, some British guru decided that it should be 50 Hz. We are, of course, still having to live with this difference but what are the advantages of one frequency over the other? Or doesn't it really matter?``` Request for Question Clarification by shivreddy-ga on 19 Nov 2002 14:25 PST ```Hi, I would be most happy to answer this question for you. Before I officially answer your question, I would like to know if the following explanation would suffice. Please indicate accordingly and I will post it as a final answer. The supply of electric power to our houses from generating stations is mainly in the form of alternating current(a.c.). However the losses experienced along the path of travel from the central power grid station to the sub-stations and then on to the distributors are phenomenal. This loss is dependent on the frequency of the a.c. supply. Along the path there are transformers, transmission cables and cores. The loss of energy in these parts depend directly on the frequency irrespective of whether the voltage is being stepped down or up. Note: Static hysteresis loss is proportional to frequency. An equation called Steinmetz equation can be employed to arrive at the fact that 60 Hz supply causes more dissipation of heat and energy than 50 Hz systems. Hence it is not preferred by many countries. The losses being proportional to the square of the frequency, is hence very high for 60 Hz systems. Now to understand the geographical areas of usage consider this extract, "North American 110-120 volt electricity is generated at 60 Hz. (Cycles) Alternating Current. Most foreign 220-240 volt electricity is generated at 50 Hz. (Cycles) Alternating Current...tape and CD players, VCR/DVD players, etc. will not be affected by the difference in cycles. IMPORTANT: Voltage converters and heavy duty transformers do not convert cycles." Modifying Foreign Electricity: "What You Should Know About Traveling Overseas With Electrical Appliances" Copyright © 2001 Hybrinetics, Inc. http://www.voltagevalet.com/foreign.html To answer your question specifically, there are no clear advantages of 60 Hz over 50 Hz except in a few cases like the one on video graphics I have considered below. Similarly 50 Hz supply which is used in India also is not of much advantage. The two systems are now standards and a transformer is requried to step up or step down from 220 to 110V or vice versa. Sometimes the difference between the two frequencies are not significant.In general, the three phase motor at 50 Hz can run also at 60 Hz, increasing the voltage of 15%, the motor at 60Hz can run also at 50 Hz decreasing the voltage of 15%, but without the tolerance ± 10% expected in the version at 50 Hz. An article with reference to effects of frequency on video display can be found here, http://members.ams.chello.nl/d.wolthers/60.html Additional Links: If you are mathematically inclined, you can see how the results in the first part of the answer were reached here: http://thayer.dartmouth.edu/other/inductor/gse.pdf A good paper which considers the effect of frequency differences on transformers can be found here, http://www.mag-inc.com/pdf/TWC-500p16-17.pdf Another paper on low frequency (30-80 Hz) trnsformers can be found here http://www.semiconductors.philips.com/acrobat/applicationnotes/ECO7703.pdf regards, Shiv Reddy```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? Answered By: shivreddy-ga on 19 Nov 2002 21:34 PST Rated:
 ```Hi, After further researching your question, I have come to realise that barring a detailed look at the effects on motors, I have covered almost all aspects of the subject. I am therefore posting it as the 'official' answer(a section is appended on motors). If you need a clarification regarding any part of the answer, I will be happy to oblige. The supply of electric power to our houses from generating stations is mainly in the form of alternating current(a.c.). However the losses experienced along the path of travel from the central power grid station to the sub-stations and then on to the distributors are phenomenal. This loss is dependent on the frequency of the a.c. supply. Along the path there are transformers, transmission cables and cores. The loss of energy in these parts depend directly on the frequency irrespective of whether the voltage is being stepped down or up. Note: Static hysteresis loss is proportional to frequency. An equation called Steinmetz equation can be employed to arrive at the fact that 60 Hz supply causes more dissipation of heat and energy than 50 Hz systems. Hence it is not preferred by many countries. The losses being proportional to the square of the frequency, is hence very high for 60 Hz systems. Now to understand the geographical areas of usage consider this extract, "North American 110-120 volt electricity is generated at 60 Hz. (Cycles) Alternating Current. Most foreign 220-240 volt electricity is generated at 50 Hz. (Cycles) Alternating Current...tape and CD players, VCR/DVD players, etc. will not be affected by the difference in cycles. IMPORTANT: Voltage converters and heavy duty transformers do not convert cycles." Modifying Foreign Electricity: "What You Should Know About Traveling Overseas With Electrical Appliances" Copyright © 2001 Hybrinetics, Inc. http://www.voltagevalet.com/foreign.html To answer your question specifically, there are no clear advantages of 60 Hz over 50 Hz except in a few cases like the one on video graphics I have considered below. Similarly 50 Hz supply which is used in India also is not of much advantage. The two systems are now standards and a transformer is requried to step up or step down from 220 to 110V or vice versa. Sometimes the difference between the two frequencies are not significant.In general, the three phase motor at 50 Hz can run also at 60 Hz, increasing the voltage of 15%, the motor at 60Hz can run also at 50 Hz decreasing the voltage of 15%, but without the tolerance ± 10% expected in the version at 50 Hz. In a motor, Eddy current losses can be examined as follows, Pe~f**2, i.e. they will increase by 44% from 50 to 60Hz. note: ~ indicates 'proportionality' For Hysteresis losses (C.P. Steinmetz Equation/Law): Ph~f**1.6, i.e. they will increase by 33.9% from 50 to 60Hz. The exponent varies from 1.4 to 1.8; however, it is generally accepted as 1.6. These losses described above produce heat that has to be removed. Accordingly one might be forced to conclude that 60 Hz systems are more lossy. However if you consider the output power and efficiency, 50 Hz systems are at a very slight disadvantage. More on this can be found here, an extract: "Pm(50) is the mech power required at 50Hz. Pm(50)=T*wm(50) where T is the torque and wm(50) is the angular speed at 50Hz. At 60Hz, wm(60)= (60/50)*wm(50) = 1.2*wm(50) so the motor runs 1.2 times more than at 50Hz....If the efficiency is constant, then A(60)= (1.2/0.9) A(50)=1.33 A(50)the apparent power increases of 33%..." Eng-tips Forums: "50 and/or 60 hz motor running suitability." Initial post by dubairay. Post by Alex68 on Sept 12, 2002. http://www.eng-tips.com/gviewthread.cfm/lev2/11/lev3/47/pid/237/qid/31684 An article with reference to effects of frequency on video display can be found here, http://members.ams.chello.nl/d.wolthers/60.html Additional Links: If you are mathematically inclined, you can see how the results in the first part of the answer were reached here: http://thayer.dartmouth.edu/other/inductor/gse.pdf A good paper which considers the effect of frequency differences on transformers can be found here, http://www.mag-inc.com/pdf/TWC-500p16-17.pdf Another paper on low frequency (30-80 Hz) trnsformers can be found here http://www.semiconductors.philips.com/acrobat/applicationnotes/ECO7703.pdf Search Strategy: 50 Hz 60 Hz difference 50 Hz 60 Hz advantage(s) I hope the above answer is satisfactory. Thank you. Regards, Shiv Reddy```
 probonopublico-ga rated this answer: ```Hi, Shiv & Neil My thanks to you both for your answer & comment: I was unaware of the matters that you have raised. With reference to India, I recall one visit to Bombay when the city had no electricity. I was told that they used a coal-fired generator but that they had run out of coal. Unfortunately, they couldn't get coal to the power station for a time because it was usually brought in by rail, along an electrified line. Kindest regards Bryan```

 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: neilzero-ga on 19 Nov 2002 17:07 PST
 ```A very few people are adversely affected by floresent tubes powered by 60 hz. The number may double at 50 hz, but I am speculating. Almost everyone is adversly affected by a single floresent tube powered by 25 hz or lower frequency as it perceived as a stobe light. Two or more phase shifted floresent tubes reduces this problem. The construction of the world's most powerful alternator would be more difficult and costly at 60 hz than at 50 hz, but the cost is essentialy the same for alternators almost that powerful. On the average, motors and transformers for 50 hz are slightly heavier and slightly more efficient than the same rating for 60 hz and the motors typically run at 5/6 the speed of 60 hertz moters. This can be either a minor advantage or minor disadvantage. The pain of electric shock increaces as the frequecy is lowered, possibly the probability of death. Hum is more dificult to reduce, but the sensitivety of the human ear to hum decreases with frequency, so that is about a tradeoff. Neil```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: roval-ga on 27 Nov 2002 10:52 PST
 ```Do you want a clear answer: “Yes, this frequency is better than the other one!”? There is no such answer! You can go in details (in different areas of electrical activity) and find advantages and disadvantages. shivreddy-ga explains how the loss of power increases for 60Hz systems comparing with 50Hz systems. We can say that is better at 50Hz. But talking about fluorescent tubes it is preferred to have 60Hz (harder to see the flickering). And, considering the explanation you received about the motor designed for 50Hz and running at 60Hz, I can tell you that is pure speculation. Nobody (that considers himself a professional) will ever do something like that. You CAN mix them up but it is NOT RECOMMENDED to do it! So which one is better? Overall talking they are about the same. But, if they have no clear advantages over the other one, why do we have two of them? I don’t know exactly, but it is very possible to have “historical” reasons! It is very possible to have political reasons: somebody decided to have a different value to prove he is different comparing with somebody else (ex: USA – England, 200 years ago). And being different can be interpreted as independent. It is possible to have “economic” reasons: somebody decided long time ago to interdict certain products coming from a country they didn’t like (to "protect" the market). Having a different standard was an easy way to justify such a "protective" measure. But all these are politics. Let’s come back to technical stuff. You asked about frequency differences. What about voltages? Here there is a clear answer: 220-240V is better than 110-120V. There are different reasons. Major one is power loss. When running 120V you have 4 TIMES more power loss in the distribution grid comparing with running same equipments on 240V. Plus you need thicker wires everywhere, better switches to connect / disconnect equipments, etc. As (almost) everybody knows: Power = Voltage x Current. For the same power: the lower the voltage – the higher the current. And, higher the current, more problems you have. Conclusion: There is no clear difference between 50Hz and 60Hz from a technical point of view.```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: shivreddy-ga on 27 Nov 2002 12:01 PST
 ```Hi, roval-ga, yes I totally agree with you. There isnt ANY clear difference between 60Hz and 50Hz. In India where I live it is 50Hz 220V - 240V and this system has its own advantages.... In the US it is 110V and 60Hz why? I dont know perhaps you could tell me? Regards, Shiv Reddy```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: probonopublico-ga on 27 Nov 2002 23:15 PST
 ```Hi, Roval Many thanks for your helpful comments. There are always 'good' commercial reasons that need to be considered. kindest regards Bryan```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: vinods-ga on 04 Dec 2002 11:43 PST
 ```Hi probonopublico, Would you please explain what you mean by this? warm regards vinods-ga```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: lookfwd-ga on 14 Dec 2002 17:34 PST
 ```There is something we should always have in mind. There may be no important difference between 50Hz and 60Hz but it is more than important to be standardized and stable. There are a lot of devices that are optimised and in fact working in either one of these frequencies. One of the most important is video, which sometimes retrieve their clock frequency from AC voltage and some clocks that do the same. I live in Greece and the voltage level is 240 V although typically it should be 220V and the frequency is not so stable as well. This causes a lot of trouble. Some PC power supply units get burned, some clocks don’t work and of course a video player that came (with the appropriate TV set) from Canada, couldn’t work although we have provided it the 220V to 110V transformer. As you can see its very important to hold the voltages and frequencies between the typical levels. * You may think that 240 V is typical but we shouldn’t forget the 5% error rate. This means that once having 240 V AC you could also have 20 seconds with 245 V. This is something that many producers forget for their money’s sake.```
 Subject: Re: AC Power Supply: 50 Hz or 60 Hz? From: probonopublico-ga on 14 Dec 2002 20:48 PST
 ```Hi, Lookfwd An interesting point! Many thanks for your contribution. Kindest regards Bryan```