[Amps] Direct rectification of AC mains to drive the amp,

[Alex Eban]

I'll tell you!
Back in the nineties at Tadiran we designed for the Navy a switching power supply based on a PFC IC the rationale was that in order to correct the power factor, it had first to make it sinusoidal, so as to resemble the voltage waveform. In this format, the input is inductive, not capacitive and the damned thing was so quiet that we had trouble convincing the inspector that the supply was working. The Navy had very stringent requirements on second harmonic generation of the mains (120 Hz),  because it interferes with sonar operation.
Alex	4Z5KS

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of peter Chadwick
Alex	4Z5KS
Sent: Friday, September 27, 2013 11:36 PM
To: Bill Turner; Amps
Subject: Re: [Amps]  Direct rectification of AC mains to drive the amp,


Bill,

As I understand it - and quite likely I' m wrong - with a normal rectifier and input C, the rectifiers draw current only when the transformer volts exceed the reservoir capacitor volts. This puts a large harmonic component on the input which isn't in phase. Using a switching  'boost inverter' allows the supply current to effectively see a resistive load.

I know the people at Alpha were telling me that meeting EU requirements was difficult with a usual transformer/ rectifier/capacitor supply, but I don't know how they got over that.

With some years of professional experience regarding EU requirements and their development, I personally feel that the Commission people have all demonstrated that they are a useless load of idiotic incompetents, busily trying to legislate things they do not understand.......

thank heavens I've retired.....





========================================
 Message Received: Sep 27 2013, 05:04 PM
 From: "Bill Turner" <dezrat1242 at yahoo.com>
 To: "Amps" <amps at contesting.com>
 Cc: 
 Subject: Re: [Amps]  Direct rectification of AC mains to drive the amp,
 
 ORIGINAL MESSAGE:          (may be snipped)
 
 On Wed, 25 Sep 2013 10:10:06 +0930, you wrote:
 
 >
 >Yes all that you mention below is correct Jim. That's why I commented in an  >earlier post that an individual QRO amp builder would get away with doing  >this questionable 3 kW power supply realization technique, but no commercial  >SS amp manufacture would be able to do this due to the electrical codes in  >respect of EU power factor rules and product compliance certification.
 
 REPLY:
 
 Power factor correction is an area I am a bit hazy on. Could someone explain  why the power factor would be different between a direct-rectified PS and a  transformer-isolated one? Either one charges the capacitors with a series of  pulses. What's the difference in power factor?
 
 73, Bill W6WRT
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