ntc inrush limiters
Seems like the cl60 thing that passlabs and others have used would be desirable and perhaps even necessary in that case, popping breakers is no fun, plus the mains switch is going to take a heap of abuse.
IIRC the cl60 has a cold resistance of about 10ohms, falling to less than an ohm once it reaches temperature, should give the switch a much longer life...
not sure if the cl60 is appropriately sized for a transformer that large, but I assume there are other devices in the series...
Stuart
Seems like the cl60 thing that passlabs and others have used would be desirable and perhaps even necessary in that case, popping breakers is no fun, plus the mains switch is going to take a heap of abuse.
IIRC the cl60 has a cold resistance of about 10ohms, falling to less than an ohm once it reaches temperature, should give the switch a much longer life...
not sure if the cl60 is appropriately sized for a transformer that large, but I assume there are other devices in the series...
Stuart
K-amps said:From what I have read, depending on the angle of the 50/60Hz sinewave at the time you engage the Toroid to the AC mains, the current draw can be as high as 800 amperes for a 1kva Toroid. this makes the caps issue seem trivial.
Actually that is an incorrect assumption, Inrush current and Instantaneous current are completely different. Current draw and time are symbiotic, Fuses, thermal devices and magnetic breakers are to slow to react to instantaneous current flow from turn on. The capacitors will draw a large amount of current for a relatively long time in the electron universe, this is the reaction that needs to be dampened via an in-rush limiter to prevent a fault detector from tripping erroneously.
The one thing a Coulomb understands is measurement of Current!
Regards
Anthony
"Instantenous or not, the current draw does exist (and has caused tripped breakers for me). The longevity of the ancilliary parts is another issue, which I did not comment on. "
It depends on at what point of the sine wave that the transformer is connected upon power up. A sophisticated circuit to only connect it at the zero crossing point would be interesting. Other wise a CL-60 would be a good inrush supressor and keep things in check there. Short it out with a small definate purpose contactor after a couple of seconds to eliminate any voltage drop from the CL-60.
Mark
It depends on at what point of the sine wave that the transformer is connected upon power up. A sophisticated circuit to only connect it at the zero crossing point would be interesting. Other wise a CL-60 would be a good inrush supressor and keep things in check there. Short it out with a small definate purpose contactor after a couple of seconds to eliminate any voltage drop from the CL-60.
Mark
There is only one problem with the theory of AC current crossing through Zero, it does'nt.
A sine wave is a flat representation of AC current looking from the side. If you look at the wave from the end it appears as a circle. The wave is actually a spiral like a coil spring. If you were to map an AC wave on a quadrant chart it would never come to o,o. lets take line voltage of 120 VAC it would move from 120,120 to -120,120 to -120,-120 to 120,-120 then back to 120,120. Mathematically it would be +,+ to -,+ to -,- to +,-
Regards
Anthony
A sine wave is a flat representation of AC current looking from the side. If you look at the wave from the end it appears as a circle. The wave is actually a spiral like a coil spring. If you were to map an AC wave on a quadrant chart it would never come to o,o. lets take line voltage of 120 VAC it would move from 120,120 to -120,120 to -120,-120 to 120,-120 then back to 120,120. Mathematically it would be +,+ to -,+ to -,- to +,-
Regards
Anthony
K-amps said:
Well wrong again, AC does not change amplitude, Neutral or a floating ground provides a Potential difference. Your example would mean that if you bridged both legs on a residential tap without touching ground you would not get a shock. Where in fact the potential difference is 240 VAC even though they are the same phase, but at two different points off the transformer.
The funtioning criteria is Potential difference that is what causes current flow, not a completed circuit per se.
Regards
Anthony
K-amps said:
If you like it is completeing the circuit, though you are actually bridging the two branches although they are in phase they are not in sync. That is why you get a potential difference.
The transformer I refer to is the Utility transformer which is a 13.6KV to 110 VAC step down off a single phase from the generating station. if you look at all hydro line the lines are in three's. Each being a different Phase, even on local streets the top three wires are three phase. This is so they can balance the load in a nieghborhood, you see not every one is on the same phase. This is why one side of the street can have power and not the other, even though you all share the same poles. The transformer has two taps and a neutral that go to each house.
The taps are on opposite sides of the coil and the neutral is grounded and center tapped. The input side of the transformer is fed by one phase and ground.
Regards
Anthony
Mark A. Gulbrandsen said:
Hello Mark, the problem is the "voltage" is always 120VAC it never changes, only it's phase angle changes. For instance 60HZ is the number of cycles per second, literally. The phase of the wave rotates through 360 Deg 60 times in one second, but it is always at 120 VAC, that's why it makes no difference where in the cycle you try to engage a circuit, it will always see maximum potential.
Regards
Anthony
"Hello Mark, the problem is the "voltage" is always 120VAC it never changes, only it's phase angle changes. For instance 60HZ is the number of cycles per second, literally. The phase of the wave rotates through 360 Deg 60 times in one second, but it is always at 120 VAC, that's why it makes no difference where in the cycle you try to engage a circuit, it will always see maximum potential."
I get ya. but really...... I'm always stay in phase" should REALLY be your signature !!!
Mark
I get ya. but really...... I'm always stay in phase" should REALLY be your signature
!!!Mark
Mark A. Gulbrandsen said:"Hello Mark, the problem is the "voltage" is always 120VAC it never changes, only it's phase angle changes. For instance 60HZ is the number of cycles per second, literally. The phase of the wave rotates through 360 Deg 60 times in one second, but it is always at 120 VAC, that's why it makes no difference where in the cycle you try to engage a circuit, it will always see maximum potential."
I get ya. but really...... I'm always stay in phase" should REALLY be your signature
Mark
Ohh how about nothing phases me!
I fear we have led this thread far a stray, my apologies everyone.
Regards
Anthony
Mark A. Gulbrandsen said:
No, it isn't. See http://www.diyaudio.com/forums/showthread.php?postid=505667#post505667
Steven
R127&R128
Hi guys, I'm working along with Jozua on the KSA50. I've managed to source most of the components, but the closest I can come to R127&R128's 25ohm is 24ohm, a 4% tolerance. SPICE simulations show no big problem, but would it be acceptable?
Secondly, is it critical to match the diff pairs (Q101-Q104) as with the Pass amps? The 100% DC feedback should eliminate the need for super-critical matching?
Thanks,
Pierre
Hi guys, I'm working along with Jozua on the KSA50. I've managed to source most of the components, but the closest I can come to R127&R128's 25ohm is 24ohm, a 4% tolerance. SPICE simulations show no big problem, but would it be acceptable?
Secondly, is it critical to match the diff pairs (Q101-Q104) as with the Pass amps? The 100% DC feedback should eliminate the need for super-critical matching?
Thanks,
Pierre
Re: R127&R128
The value of the resistor is not critical. The matching of the transistors is good, but also not critical.
I always match all the components, especially from channel to channel. But for the transistors that is either beta match for bipolar or "on" resistance for fets. This way the channels act about the same in operation.
Matching the resistors helps prevent problems from time to time. I have had problems before where it was traced to a resistor that was either mismarked or just way out of value. I always thought it was damaged either by installing or from actual use.
But now when matching all the resistors, I find brand new resistors that measure way off from time to time. This happens with my preferred AB carbon comps and also with 1% metal film and cermet types. I just throw those away.
George
PWatts said:
The value of the resistor is not critical. The matching of the transistors is good, but also not critical.
I always match all the components, especially from channel to channel. But for the transistors that is either beta match for bipolar or "on" resistance for fets. This way the channels act about the same in operation.
Matching the resistors helps prevent problems from time to time. I have had problems before where it was traced to a resistor that was either mismarked or just way out of value. I always thought it was damaged either by installing or from actual use.
But now when matching all the resistors, I find brand new resistors that measure way off from time to time. This happens with my preferred AB carbon comps and also with 1% metal film and cermet types. I just throw those away.
George