TheMG
join:2007-09-04
Edmonton, AB
 ·TELUS
| reply to Anonymous_
Re: Daisy chaining power strips
said by Anonymous_  :the wal-mart amp has a toroidal core transformer as i opened it up to *see * what cheap parts are used 80 (95)VA to 120 (145) VA toroidal core transformer Which means jackshit. Any manufacturer could decide to stick a toroidal transformer in and claim the amp is high quality. Toroids aren't really a sign of quality, but they do have some advantages, mainly smaller size and weight compared to their E-I core counterparts. Traditionally they were more expensive, but I'm not sure if that's the case anymore.
The only way to tell if the amp is a good design and lives up to its expectations is to put it through its paces in a series of bench tests.
For one this means running the amplifier up to its rated power output into a dummy load and measuring distortion using a distortion analyzer. That's the most basic test, and the one where poorly designed or overrated amplifiers will fail.
Distortion in excess of 1% THD at the amplifier's maximum rated power level could be considered a failure. Many consumer grade amplifiers tend to have distortion levels as high as 10% at their max rated power. |
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SmokChsr
Who let the magic smoke out?
Premium
join:2006-03-17
Saint Augustine, FL
| reply to Anonymous_
said by Anonymous_ : the wal-mart amp has a toroidal core transformer as i opened it up to *see * what cheap parts are used 80 (95)VA to 120 (145) VA toroidal core transformer Quite a bit of newer equipment is using toroid wound transformers, it's primarily for size reduction, it fits better. If it's rated at 145VA then you pretty much know it'll only be capable of about 100W RMS power Max, more likely close to 35W power out. |
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srr2
join:2001-12-20
Bethlehem, PA
 ·RCN CABLE
| reply to TheMG
The greatest advantage to a toroidal power transformer is its lack of an external magnetic field. That can yield enormous advantages in the design of low-noise circuitry that has to be positioned physically close to it. I've never seen a size advantage to a toroid, but maybe those who have are using really expensive core material. |
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public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
| said by srr2 :The greatest advantage to a toroidal power transformer is its lack of an external magnetic field. That can yield enormous advantages in the design of low-noise circuitry that has to be positioned physically close to it. I've never seen a size advantage to a toroid, but maybe those who have are using really expensive core material. Toroids still leak just a bit less. The shape is preferred for switching transformers because of significantly lower parasitics.
The smaller size of 60 Hz units means higher design flux, and hence higher inrush current. Toroids designed by an idiot can blow huge cartridge fuses on power on, and can easily burn socket strips.
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An_Onymous
join:2009-10-24
Canada
| >The shape is preferred for switching transformers because of significantly lower parasitics.
Parasitic is determined largely by how the coil is wounded and core material. Can you please elaborate?
R - your magnetic material, copper losses etc
C- how you overlap the windings make more difference.
Aside from the geometry of the material (toroid vs EI cores), leakage inductance is also determined by the amount of coupling between windings. Bifilar windings has lower leakages etc. |
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public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
| said by An_Onymous :Parasitic is determined largely by how the coil is wounded and core material. Can you please elaborate? Aside from the geometry of the material (toroid vs EI cores), leakage inductance is also determined by the amount of coupling between windings. Bifilar windings has lower leakages etc. Parasitics have little to do with the material. Mainly configuration. Bifilar is good, shell even better.
Main point is that with no gap high flux 60Hz designs the inrush current can be destructive. |
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An_Onymous
join:2009-10-24
Canada
| >Parasitics have little to do with the material.
Core losses etc does not exist in your Universe of high frequency transformers!?
>Mainly configuration.
And yet you suggested that toroids have lower parasitics for switching transformers... Coils configuration are different than core geometry. :P
>Main point is that with no gap high flux 60Hz designs the inrush current can be destructive.
That part I did not argue with.  Toroid material can have internal air gaps based on the mix.
The inrush current only last a few cycles and the current decay exponentially. This happens when the current is switched on at zero crossing and saturated the core. Also a matter of picking a slow/time delay fuse correctly.
An idiot could wired up the center tap incorrectly i.e. connect 2 windings in series backwards etc too. ;P Nothing is fool proof. |
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Mdoc
Ehh... munch munch... what's up, Doc?
join:2007-03-27
Sterling, VA
4 edits | reply to Anonymous_
i have a
Large 30"CRT Trinitron
5.1 system
Playstation 3
playstation 2 USA
playstation 2 Japan
External HDD
Cable Box
Computer
Fridge (full size)
another 5.1 system for my computer
and one LCD Monitor
all pulged into 1 20 amp circuit
Sure, I believe that can be done safely. But you can't add much more in the same circuit branch in the room, unless you want to blow a circuit breaker.
I wouldn't do the daisy-chaining of power strips for aesthetic reasons, but I've done this at work to "bridge" the distance gap. As someone already mentioned here, just pay attention to the total current draw. But sometimes you don't know what it is until you actually sit down and do the calculations for not just the power strip current draw, but also the current draw of the entire circuit branch from the breaker box that the power strip(s) is connected to.
And yes, I have connected equipment in daisy-chained power strips and have blown a circuit breaker because of it. There was no fire. If there's nothing but one or two equipment connected to a daisy-chained power strip, there's no hazard esp. if they don't draw too much power. However, I don't implement daisy-chained power strips as a permanet application, even at work. It's strictly a temporary application.
And I've even turned everything on in my basement den except my laserprinter; and when I turned on my printer, the circuit breaker tripped and the room went dark. And I didn't use no stinkin' power strip.
And I think both the zero daisy-chain opinion and the entire discussions in this thread are ridiculous.  Got a few laughs, though.
Keep in mind that some strips have resetable fuses built into them--typically no more than 2 amps (for short strips). Any overcurrent will trip that fuse instead of the breaker box.
edit: corrected quoting problem |
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