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DCR requirments for Chokes

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each tube data select adeguate inductance for input choke with low DCR but read Sowter page, : "choke input filter chokes provide somewhat better regulation of the power supply though are much larger."Please specify the inductance and DC current capability you need. You can also specify the D.C. resistance or leave this to us. In this case it will be determined by the current rating of the wire but we will thicken up the wire to minimize the resistance if we have space on the bobbin. If you specify a resistance value the choke may be larger. We can design chokes for choke input or capacitor input filters. If you specify a choke for a choke input filter we need to know the rms ac voltage feeding the rectifier output as the choke must support this voltage. The choke in a capacitor input filter only sees a small ripple voltage. Chokes for choke input filters are generally at least 50% larger. "

we live with EMI but i use to pour epoxy inside HT transformers and choke bells or potting input choke and adeguate rotation before drill mounting holes. ground line short , RC tuning, wire resistors and good caps
 
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Generally, there are no particular requirements of for dc resistance in power supply chokes for tube equipment, regardless of choke input or capacitor input. The higher the DCR the better the filtering (hum suppression) but given the inductance dominates, you'll never notice, and the worse the regulation. But is not at all critical, especially if the output stage is Class A.

If you specify a choke on the basis of the amount of DC it must carry and the inductance required at that current, you won't go far wrong.

A possible exception is where a shunt capacitor is used across the choke in a phase cancellation scheme - this can give very low ripple with small components. This technique is rarely used.
 
Sumotan: Yes, connected to the two connections of the choke. This means the ripple AC goes thru the choke and gets phase retarded, and through the capacitor and gets phase advanced. If you get the phases arriving at the choke output end in opposition, the AC component is cancelled out, but only at one frequency (120 Hz in American countries and Japan; 100 Hz elsewhere).

It's rarely used because with it the design must match the supply frequency (no good for export), because it passes any hash/noise from the mains straight through, and also because if the DC load varies, as the inductance of a choke depends on the DC flowing in it, the cancellation is hardly ever perfect. The capacitor must be chosen to match the choke inductance, DCR, and core loss. A mismatch can makes things a lot worse instead of better.

But you see it occasionally, so I thought I would mention it because if I didn't some smarty pants would bring it up as an exception to the rule that choke DCR doesn't matter much in practice.
 
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Sumotan: To calculate it is somewhat involved and depends on some uncertainties, particularly for low values of the first filter cap.

The best approach is C = 1 / (4 L pi-squared f-squared)
where C is the shunt capacitor in farads, L is the choke rated inductance in henries, f is the ripple frequency in Hz, pi is 3.14... .
Try that value as a starting point, and then go down in 5% increments until you spot the optimum ripple reduction.

Note that the cap may operate under some stress if the initial ripple is quite high in a high power amplifier. This is about spending money on a capacitor to save money in the choke. It's not particularly recommended. Just another option. These days, if you have got a bit too much ripple, just put in a bigger second electrolytic. There's no limit other than your wallet. (Don't increase the size of the first electrolytic beyond the rectifier tube ratings - all tube rectifiers have a maximum allowed first filter capacitance. If this capacitance is exceeded, they can arc over internally, with dramatic results.) When tubes were king, you couldn't get electrolytics in decent sizes.
 
To answer your question, The DC resistance is basically a loss.... You try to keep it minimized else the inductor would be HUGE to accommodate to large of a wire gauge... The DC resistance and Inductive reactance are added vectorially ..... The DC resistance in some cases decrease the Q of the LC resonant tank circuit.... ie it can help "dampen" the resonant frequency peak in circuits that could otherwise ring, which can be a good thing, due to the fast change in phase angle..
 
Thank you kindly Cerrem. The reason that I put forth this question was while surfing I came across an article saying LC inductors should have dcr of no more then 200 ohm while CLC can be higher. I've never come across such recommendations when I was reading up of tube articles, hence.
 
For a true choke input filter, you need to meet the rule for critical inductance:
Critical Inductance = 350/(current in mA)

A choke input filter for an amplifier that needs 80mA DC will need an inductor of:
350/80mA = 4.375 Henry. Use a 5 Henry inductor.

A choke input filter gives DC volts that is 0.9 x rms Volts. A full wave 400-0-400 VAC primary is rectified by low voltage drop Schottky diodes. The DC voltage out is 400 x 0.9 = 360VDC. As stated earlier, you need a choke that is rated for choke input service application. Otherwise, stick to capacitor input supplies.
 
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the question was about DCR between swinging and smooting choke DCR and 6A3summer you do not consider coil res DCR and for HV valve psu consider 10H racomanded value in real world swinging choke DCR should be as low its possible for low noise and better regulation i think Schottky diodes rectifiers etc good only for heather and smps
 
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claudiomas,

I mentioned some facts, in case the original poster might be interested in using a choke input power supply.

As was already said, low DCR is important. I was not going to repeat what had already been said.

Failure to follow the critical inductance rule is allowed. But if you do, the power supply is not a true 'choke input' power supply. It will not output 0.9 x the rms volts, but will in fact be more toward a cap input filter supply (outputs up to 1.414 x rms volts). If you observe Both critical inductance, And low DCR, you will get good power supply regulation versus load current.

There are HV Schottky diodes (or even if there are not any), then . . . Whatever reasonable solid state HV diodes you use, they have lower impedance and voltage drops than tube rectifiers that are commonly used in the same circuits. As such, the solid state diodes also give better voltage regulation versus current when the filter is a true choke input.
 
thanks 6A3summer for the point valves in psu are most protecting the DUT or OPT or amplifier wathsoever also sometime look great if any problem the valve will not over destroy and short anything, with diodes if any moskito fly in the wrong way the diode go short and your opt tamura tango etc bye bye many time i get amplifier on the repair bench with power transformer and one OPT dead @ the same time killeds by one small cheap diode, so if somebody really want use diode rectification way not insert one valve just to protect and give the other tubes the time to be ready to draw current before HT come on

cheers
 
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