Connecting a Meanwell s-350-27 to the mains power

[Billyo]

I'm gradually accumulating the components to make my first speaker build. Today the Meanwell S-350-27 PSU arrived.

I was anticipating that I could use a "jug plug" to plug it into the mains power (240 V AC in Australia), but was a bit taken aback that it looks as though the 3 wires from a mains power cord need to be stripped back and individually connected to the inputs.

Is this normal practice for everyone to do this? Frankly, mucking around with mains power isnt something that I like doing much, and I'm concerned that perhaps I've got the wrong end of the stick somehow and bought completely the wrong PSU.

Can someone please just give me reassurance that I'm not completely deluded here.

ta

b

[mastodon]

Well, since you're building your own equipment, you'll also have to take care yourself of peripheral stuff such as net entry. So no, you're not deluded. I would recommend installing a power socket so that you can use a regular power cord to connect your amp to a wall outlet.

[Billyo]

Hmmm... I understand that its illegal here to DIY your own wiring with mains power, and given the lethal consequences of getting it wrong, I'm sort of inclined to agree.

I guess that leaves me in a bit of a dilemma... I was hoping to avoid using a receiver

[Billyo]

I don't think that all is lost however... what I might do on the weekend is take the PSU around to an electrical service center and get them to wire in a cord and then encase the naked terminals in an epoxy resin to completely eliminate the chance of them ever being shorted or worse, touched by anyone (like my curious kids).

Further, I'll build the amp in a plastic instrument case and bond the PSU to the bottom of the case rather than screw it on. That way, even if the PSU case becomes live somehow, it can't electrify the instrument case.

It looks as though the case is grounded anyway, judging by the circuit diagram at http://www.meanwell.com/search/se-350/default.htm

[mb3]

I'm guessing you are brand new to all this but this is a very basic, simple job. All you need is to buy a plug and a length of 3-wire cable. Then all you need to do, after stripping a little at the end of each wire, is to correctly connect each wire to Live, Neutral and Earth. This is labelled on the meanwell.. probably also on the plug too, but if not you can always google it. Screw them in tightly and there will be no chance of shorting. There are plastic 'barriers' inbetween the connections as you can see if you look. They also invented fuses to prevent such things causing big problems.

This is virtually the exact same thing you are going to have to do at the output going to your amp, just that it will be 27V DC that end. You don't do any of this whilst there is any power going through so as long as you take even a small amount of care it carries no significant danger.

I am almost certain that this 'illegal mains wiring' refers to the actual wiring within your house. IE. in your walls; not just any device that takes mains (that would be, absolutely everything that uses electricity).

[Billyo]

Yep - brand new and a complete babe in the woods when it comes to most things audio. I called an electrical place on Thursday and was going to drop in this morning - but the sulky girl who answered the phone neglected to tell me that they're address in white and yellow pages is completely wrong. so wasted an hour of my valuable Saturday morning walking up and down a street wondering where I'd gone wrong.

Looks like I'll be wiring it myself! Save a few bob as well.

Thanks for your help.

[VivaVee]

Originally Posted by mb3

I am almost certain that this 'illegal mains wiring' refers to the actual wiring within your house. IE. in your walls; not just any device that takes mains (that would be, absolutely everything that uses electricity).

WRONG.

In Australia & NZ, Limited Electrical Registration is required before you can legally perform repair work on a piece of mains powered equipment. This is the case whether the repair person is working on a toaster or an amplifier. Full Registration is required before you can legally manufacture/build/assemble primary/mains wiring. In a factory setting, the build/assembly is done by un-registered personnel and then checked by a registered person.

What you actually do is up to you and your conscience.

But if you are new to this game and are (rightfully, in my opinion) nervous around 230V mains voltages, then I recommend that you wire up the SMPS module and then have it checked by an electrician or person with full registration. Which is pretty much what your were thinking of doing anyway...

[Billyo]

Today I bought a length of 3 core mains power cable, a C14 socket with a fuse holder and a synthetic rubber cover to go over the terminals on the back of the socket.

I'll strip back the sheath of the cable and trim the live and neutral so that they're a little shorter than the ground - the idea being that the ground would be the last that would break away should it somehow get yanked (unlikely anyway, since the socket will prevent any pulling from outside the case).

As for value of the fuse, the SMPS can deliver 13 A and I was intending to run it at around 24VDC, implying power of 13x24 = 312 W.

From browsing other posts it seems that the appropriate fuse value is 312/240 * 3 - with 3 being a factor to cater for power-on surges - i.e. 4 A AC fuse would be used.

Also, the general consensus is that a slow-blow fuse is preferable over a fast-blow.

Frankly that fuse value seems a bit high to me. Would say 2.5 A be just frustrating with blows all the time? Are my calculations way off?

I've used as maximum the power rating of the SMPS - would it be better to use the maximum power rating of the loudspeakers instead?

[Mark.Clappers]

Hello,

I use the same power supplies from Meanwell in my power amplifier, actually I use 2 to get a bipolar supply.

I would advice not to use a fuse rated at (almost) the same current as the application will draw, these power supplies do have a rush in current when powered up and this could cause your fuse to blow without there being an actual fault condition or during a high current transient.

I use a 5A fuse for complete power supply (640 watts output), in the Netherlands we also have 230VAC. This will blow (quickly) if there is fault condition but is still completely safe. So I would say something like 3A fast or slow blow should fit you application nicely. Just my 2c!

[Billyo]

Thanks Mark, I'll try a 3A slow blow tomorrow.