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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Sun Feb 14, 2016 7:13 pm Post subject: OT running A/V equipment on a generator |
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How far from 60 Hz would it be safe to wander without damaging equipment? I am breaking in a new generator and while it was running (NO LOAD) I decided to test the Hz and it was 64. I plugged in a shop vac and it dropped to 62 Hz. I know I can adjust the governor to reduce the rpms if I have to
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Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Mon Feb 15, 2016 8:45 am Post subject: |
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Hi,
the AC frequency will affect linear power supplies (using a large transformer) more than modern switch-mode power supplies.
Transformers will only reach their optimum efficency when fed with AC using the frequency they were designed for. Otherwise, reduced output voltage/current may occur and self-heating may be increased.
Switch-mode Power supplies rectify the AC voltage to DC which eliminates the AC frequency variation. The subsequent inverter stage converts DC to AC by running it through a power oscillator, whose output transformer is very small with few windings at a frequency of tens or hundreds of kilohertz. Some of these power supplies can be fed with straight DC too.
In general, a variation of less than 10% on the AC frequency shouldn't create any significant problems. You may consult the manuals of Your A/V gear. There may be some information on AC frequency limits.
Control of the generator RPMs can be achieved using several different methods. Maybe the generator's manual will shed some light on this. Or You could find some information on the web looking up its model number...
Regards,
barclay66
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Mon Feb 15, 2016 2:45 pm Post subject: |
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Actually I disagree. What will kill a device, both linear and switching supplies is the lack of a good sine wave. Many lower end generators use a 'modified' sine wave output, which can kill power supplies. A bit of drifting in the frequency won't do anything, in fact many devices have 50/60 Hz power supplies (like the Marquee, and many vintage stereos that are switchable), so that's not an issue.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Mon Feb 15, 2016 3:33 pm Post subject: |
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| Curt Palme wrote: | | Actually I disagree. What will kill a device, both linear and switching supplies is the lack of a good sine wave. |
I see nothing that disagrees with what I wrote. I only focused on the frequency issue. He didn't mention anything on the waveform which led me to believe it was OK, but You're right adding it as another (maybe more important) factor.
| Curt Palme wrote: | | Many lower end generators use a 'modified' sine wave output, which can kill power supplies. |
Right. The waveform should be verified using an oscilloscope before connecting expensive equipment to the generator. The tricky part is that the waveform may vary depending on the type (inductive/capacitive/resistive) and amount of load.
| Curt Palme wrote: | | A bit of drifting in the frequency won't do anything, in fact many devices have 50/60 Hz power supplies (like the Marquee, and many vintage stereos that are switchable), so that's not an issue. |
I think that this sums up what I wrote before...
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Mon Feb 15, 2016 4:46 pm Post subject: |
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I was only disagreeing with what you said about standard linear transformers. While yes, they do have a bandwidth, and a 60Hz transformer probably won't do well at 400Hz, it will work equally as well at 50 or 70hz.
( I saw an installation about 20 years ago where a competitor used a 110 volt to 6.3 volt filament transformer as an audio transformer. (!!!) Needless to say, we pulled it out.)
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