[time-nuts] OT: Re: HP and other equipment failure

J. Forster jfor at quikus.com
Mon Jun 17 12:55:03 EDT 2013


I assume you mean the markup. If you think that's high, just look at what
a hospital charges for an Aspirin or a Band-Aid.

YMMV,

-John

================


> That's criminal!
>
> Tom
> ----- Original Message -----
> From: "J. Forster" <jfor at quikus.com>
> To: <nerd at verizon.net>; "Discussion of precise time and frequency
> measurement" <time-nuts at febo.com>
> Sent: Monday, June 17, 2013 12:43 PM
> Subject: Re: [time-nuts] HP and other equipment failure
>
>
> An Audiophool and his money are soon parted.
>
> -John
>
> ===============
>
>
>
>> The current distortion from simple transformer-rectifier-capacitor power
>> supplies contains a lot of third harmonic content.  In a 3 phase system
>> (as are
>> all distribution systems for commercial and industrial) the third
>> harmonic
>> ADDS
>> in the neutral, or creates circulating currents in a delta
>> configuration.
>> These
>> currents, as you mention, can get very large and were the cause of many
>> transformer explosions in cities as these power supplies became common.
>> The
>> transformer designs had to be improved, but the PFC supplies make a big
>> difference.
>>
>> How many of you have looked at the power line waveform, especially in an
>> industrial or commercial area?  Doesn't look much like a sine wave, does
>> it?  So
>> it's pretty funny to see audiophile outlets
>> (http://www.dedicatedaudio.com/power_outlets).
>>
>> Peter
>>
>>
>>
>>
>> On 6/15/2013 6:56 PM, stan, W1LE wrote:
>>> PFC to me is power factor correction, not only the classical power
>>> factor to
>>> minimize (VAR) volt-amp reactive component,
>>>  but also to remove the harmonic load  current imposd on the electrical
>>> power
>>> system.
>>> A '90's onward technique. in th 80's and 90's without the harmonic load
>>> current reduction and having
>>>  a few 100 end items of equipment, each withtheir own  a switch mode
>>> power
>>> supplly,
>>>  it was not uncommon to find hundreds of amps of the third harmonc on
>>> neutra,
>>>   in the electrical power distribution system.
>>>
>>> Could be a serious EMC problem if you were dealing with voice grade
>>> channels.
>>> And people safety issues.
>>>
>>> Stan, W1LE   Cape Cod
>>>
>>>
>>>
>>> On 15-Jun-13 5:52 PM, J. L. Trantham wrote:
>>>> Sorry for the interruption but what is 'PFC'?
>>>>
>>>> Thanks.
>>>>
>>>> Joe
>>>>
>>>> -----Original Message-----
>>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]
>>>> On
>>>> Behalf Of Poul-Henning Kamp
>>>> Sent: Saturday, June 15, 2013 4:09 PM
>>>> To: Robert Atkinson; Discussion of precise time and frequency
>>>> measurement
>>>> Cc: Perry Sandeen
>>>> Subject: Re: [time-nuts] HP and other equipment failure
>>>>
>>>> In message
>>>> <1371329221.83869.YahooMailNeo at web171902.mail.ir2.yahoo.com>,
>>>> Robert  Atkinson writes:
>>>>
>>>>> While I agree with everything else you say, you CAN have too much
>>>>> filter capacitance. At least where dc rectifier / filter (smoothing)
>>>>> circuits are concerned. Increasing C causes increased ripple current
>>>>> [...]
>>>> And ripple current can be a major source of power-line frequency noise
>>>> in
>>>> all electronics.
>>>>
>>>> The main reason why switchmode power-supplies today (can) outperform
>>>> linear
>>>> power supplies with respect to noise, is because the legally mandated
>>>> PFC
>>>> correction eliminates the bridge-rectifier ripple harmonics.
>>>>
>>>> I would not hessitate to use a good quality switchmode to replace the
>>>> linear
>>>> supply in a HP5370B.
>>>>
>>>> I did some experiments a couple of years ago, with an audio-amplifier:
>>>> I put a standard PFC corrector chip on the secondary side of the
>>>> trafo.
>>>>
>>>> The overall result was not satisfactory, but the 50 Hz "sneer"
>>>> we all know and hate was absent, and the "Tzoing!!!!!" power-on
>>>> mechanical
>>>> shock from the trafo was also eliminated, as was the consequent
>>>> dimming
>>>> of
>>>> the lights ;-)
>>>>
>>>> The main reason not to do this, is that you need some physically
>>>> gargantuan
>>>> coils for a 10A+ PFC-switcher.
>>>>
>>>>
>>>
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>>
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