Clayphish

Power cables and cables in general -- distinctions(?)
« on: April 27, 2006, 09:05:50 PM »
Hi again.  :oops:

maybe I'm over complicating this, I don't know..

Basically I'm having problems understanding what type of cable would be more appropriate for use in power transmissions. (ie 4/5 conductor cable from a PSU to Mixer). I've been looking at a few online stores and I gotta say there is a lot of different types of cable available.

As of right now, my needs are to send 325vdc @ 40mA and 12.6vdc @ 3 amps to a tube mixer.

So where do I start? Heres a couple questions

1. Looking at the wire current limits chart am I right in thinking 16 awg is enough?
2. How do I determine overall thickness and flexability when choosing?
3. Is the outter jacket important when choosing the type (Neoprene, PVC, etc.).
4. Is the insulation material important?
5. Is insulated cable used solely for this application?
6. In searching I've seen some mention of "control" cable.. is this whats generally used?


Thanks for helping. Maybe if this is worth while it can be added to the wire meta.
Looking for McCurdy PE1000 console Schematic


PRR

Power cables and cables in general -- distinctions(?)
« Reply #1 on: May 05, 2006, 02:46:51 AM »
> maybe I'm over complicating this

I think so.

#16 should be ample, unless the run is very long.

Flexibility: whatever feels good and will last. In casual DIY, not very important. Likewise, neoprene and PVC and lead-sheath are important for Rough Service or around gasoline or underwater, but in a studio it really isn't important.

Control cable is different from power cable, but your ~50 Watt load is similar to many control jobs rather than to KiloWatt power loads, and will be fine.

pstamler

Power cables and cables in general -- distinctions(?)
« Reply #2 on: May 05, 2006, 03:24:01 AM »
One spec to watch is the DC voltage rating of the cable, at least the one you're using for B+. You're planning on 325V, but if the line voltage runs 10% high (and the B+ isn't regulated before it hits the cable) you could actually be passing 357V, which means a cable rated to 350V won't really cut it.

Surprisingly, Canare Star-Quad microphone cable is rated for 500V DC; I use that for carrying B+ with full shielding, bundled with some heavier-gauge stuff to carry filament supplies (also shielded, but it doesn't need as high a voltage rating).

Peace,
Paul

bcarso

Power cables and cables in general -- distinctions(?)
« Reply #3 on: May 05, 2006, 05:30:30 AM »
Quote from: "pstamler"
One spec to watch is the DC voltage rating of the cable, at least the one you're using for B+. You're planning on 325V, but if the line voltage runs 10% high (and the B+ isn't regulated before it hits the cable) you could actually be passing 357V, which means a cable rated to 350V won't really cut it.

Surprisingly, Canare Star-Quad microphone cable is rated for 500V DC; I use that for carrying B+ with full shielding, bundled with some heavier-gauge stuff to carry filament supplies (also shielded, but it doesn't need as high a voltage rating).

Peace,
Paul


That's a nice spec to know, Paul.

I would add that you will probably be o.k. if you are careful about minimizing flexing of "everyday" wire and watch that it doesn't rub against sharp edges and openings.  If this were a commercial product there are very specific regulations about the type of insulation etc.

Clayphish

Power cables and cables in general -- distinctions(?)
« Reply #4 on: May 05, 2006, 05:50:39 PM »
Quote from: "PRR"
> maybe I'm over complicating this

I think so.

#16 should be ample, unless the run is very long.

Flexibility: whatever feels good and will last. In casual DIY, not very important. Likewise, neoprene and PVC and lead-sheath are important for Rough Service or around gasoline or underwater, but in a studio it really isn't important.


I think this is whats been screwing me up. On all the manufacturers websites, they were refering to outdoor use, including the use of being underground and in water. Really, I just want a simple flexible cable that will do the job..      :grin:

Thanks for letting me know I'm over doing it though.
Looking for McCurdy PE1000 console Schematic

Clayphish

Power cables and cables in general -- distinctions(?)
« Reply #5 on: May 05, 2006, 06:01:24 PM »
Quote from: "pstamler"
One spec to watch is the DC voltage rating of the cable, at least the one you're using for B+. You're planning on 325V, but if the line voltage runs 10% high (and the B+ isn't regulated before it hits the cable) you could actually be passing 357V, which means a cable rated to 350V won't really cut it.

Surprisingly, Canare Star-Quad microphone cable is rated for 500V DC; I use that for carrying B+ with full shielding, bundled with some heavier-gauge stuff to carry filament supplies (also shielded, but it doesn't need as high a voltage rating).

Peace,
Paul


Hey thanks Paul, that really helps me out. Do you happen to know off hand what online store carries the star quad cable?


Quote from: "bcarso"

I would add that you will probably be o.k. if you are careful about minimizing flexing of "everyday" wire and watch that it doesn't rub against sharp edges and openings. If this were a commercial product there are very specific regulations about the type of insulation etc.


You know this is probably the one thing I wish I knew. Seeing that i'll be running approx 325 volts into a mixer, it makes me wonder if these regulations would be a good addition  to the metas on this website..  just for safety reasons or even a guideline for some who don't know them.
Looking for McCurdy PE1000 console Schematic

bcarso

Power cables and cables in general -- distinctions(?)
« Reply #6 on: May 05, 2006, 06:59:41 PM »
Quote from: "Clayphish"

You know this is probably the one thing I wish I knew. Seeing that i'll be running approx 325 volts into a mixer, it makes me wonder if these regulations would be a good addition  to the metas on this website..  just for safety reasons or even a guideline for some who don't know them.


Safety/agency stuff is a whole area of expertise, and a treacherous one---remember what UL stands for.

pstamler

Power cables and cables in general -- distinctions(?)
« Reply #7 on: May 06, 2006, 03:43:43 AM »
Quote from: "Clayphish"
Quote from: "pstamler"
Surprisingly, Canare Star-Quad microphone cable is rated for 500V DC; I use that for carrying B+ with full shielding, bundled with some heavier-gauge stuff to carry filament supplies (also shielded, but it doesn't need as high a voltage rating).


Hey thanks Paul, that really helps me out. Do you happen to know off hand what online store carries the star quad cable?


Pro Cables 'n' Sound has it in bulk, by the foot; so does Markertek, but you'll have to search on their site for it. You want the L-4E6S cable. Oh, one correction: I said it was rated for 500V DC; it's actually rated for 500V AC, but 500V DC should be no sweat. It's certainly carried ~360V DC for me happily.

Peace,
Paul

PRR

Power cables and cables in general -- distinctions(?)
« Reply #8 on: May 06, 2006, 09:48:52 PM »
> One spec to watch is the DC voltage rating

Well, yeahbut... a good coat of paint will stop 300V. Most plastic insulation is sized for mechanical toughness, not for voltage. And an awful lot of it is rated 300V exposed, 600V inside the chassis, just because any decent plastic will stand many hundreds of volts.

> If this were a commercial product

Right. Then you need two engineers and five lawyers for every product. But for personal use in a studio, almost anything that doesn't feel flimsy under the strippers will be fine.

FWIW, I've used multiple lampcords laced with twine. It's rated 300VAC, I would not worry about 300-400VDC. It's fairly tough. When abuse threatens insulation breakdown, it is dirt-cheap to make-up another. These days you can get spiral-wrap for automotive wiring dress-up for another layer of protection (and without learning the lost art of lacing wiring).

PRR

Power cables and cables in general -- distinctions(?)
« Reply #9 on: May 10, 2006, 05:24:23 PM »
> One spec to watch is the DC voltage rating

But see Ken's tests: "I've made twisted pairs of 300v wire and cranked the voltage up on a hipot tester.  You have to get the voltage up to about 3000-4000 volts before the wires arc over."

We can quibble that, although it does not break-down in a minute of furious cranking, it may slowly decay over years of sustained high voltage. New spark-plug wires get not-new in a few years: heat, oxygen, and strong electric field eventually corrupt the plastics. Yet as a real-world test, lots of 450V guitar amps are wired with "300V" wire and live for decades. And conversely, if sparkplug wires stand 40KV spikes, quite thin plastic should hold >1KV, and certainly a few hundred volts.


 

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