If an AC wallwart is rated for X amount of current on the secondary, what parameters does that rating fall under?
Is it for maximum current pulse per cycle?

 

What type? AC out?
There is the older linear version or the later/current SMPS versions.
With the former type, the rated output voltage is when drawing rated current.
SMPS is the current drawn by the item it is feeding.
Max.

 

Here is an example of a simulation of the power supply ripple currents in an audio amplifier delivering 3 watts into 8 ohms.

Huge turn on transient and 9A ripple per half cycle.
The wallwart I'm using is rated at 1500ma.
What I want to know is if I'm killing my wallwart or is it safe? At what point does it become unsafe to the wallwart?

 

Here is an example of a simulation of the power supply ripple currents in an audio amplifier delivering 3 watts into 8 ohms.
Huge turn on transient and 9A ripple per half cycle.
The wallwart I'm using is rated at 1500ma.
What I want to know is if I'm killing my wallwart or is it safe? At what point does it become unsafe to the wallwart?

No matter what the simulation says, your power supply isn't delivering anything like that. The rating is capacity. Even at a dead short, the supply isn't going to provide 9A nevermind 100A.

 

I've randomly killed 2 walwarts recently.
There must be a rated safe limit.

 

Anyone?

 

Of course there is a safe limit. But I can not understand your question. We need to know exactly what you are trying to do.

And that includes what components you are trying to do it with.

 

I want to know what the current rating on a wallwart means. I'm trying to stop killing them when powering circuits.

 

There are no laws on how much current a wall wart can supply. They come in all kinds of current ratings.

Have you looked at the label?

 

People are giving me conflicting advice here.
How to I asses which walwart is proper for X circuit?
As I said above the circuits I'm using should have power supply ripple currents far above the rated current draw of the walwart.
Sometimes my walwarts die randomly and sometimes they don't.
I don't know what conditions the rated current of a walwart apply.

 

Because........it depends on what "X" circuit is.

 

Anyone?

First, let me get the bitching and complaining out of the way,
You can't expect useful answers if you give us zero information to work with.

I will assume that you are trying to power an audio amp.
How much power do you expect to get out of your amp ?
And, secondarily, will the amplifier be powering speakers that
can withstand the expected power ?

You can sorta/kinda guesstimate the amount of power your wall wart
will put out by applying Ohms Law.
the one you described puts out 1.5 amps, multiply that by the supplied voltage,
and you will have some idea of the amount of power available for the amp.
Although this can vary widely since it most likely is not regulated,
and the voltage will "sag" under load.

The voltage output rating also needs to be matched to the needs of the amp and
its intended load, ( 8 ohm speaker / headphones only ).

My first guess is that you haven't thought this out,
and have seriously over-blown expectations,
such as rockin' the house with a 10 watt wall wart, and 3" speakers.
This is a common occurrence with people new to electronics and sound.

Although I don't know what you actually expect,
you would probably be better off starting with a Lap-Top power supply,
these are usually around 20volts output, at around ~1 to ~4 amps and
usually have substantial built-in protection circuitry,
so you are less likely to smoke it.
The larger ones are capable of supplying a 20watt 2-channel amp,
which, with a good set of speakers, can put out some fairly decent volume.
However, this kind of power will quickly smoke a set of 3" speakers.

Unless you are in this for the adventure and satisfaction of doing it yourself,
I would suggest that you go to Parts Express and buy one of their ready-made
Class-D Digital Stereo Amps, which come with a matched power supply.
You can also find some very good, cheap speakers, and links to DIY Forums.

 

Here is an example of a simulation of the power supply ripple currents in an audio amplifier delivering 3 watts into 8 ohms.

No, it isn't.

For 3 W into 8 ohms, the peak current is 0.87 A. Peak-to-peak current is 1.73 A. Also, the initial current surge while the supply charges up the filter capacitor is irrelevant. Also, it is not 90 A. Your model does not take into account any of the characteristics of a real world transformer.

You still have not said if the output of the wall wart is AC or DC.

There are three types of wall warts: AC output, DC output switching, and DC output linear. Without this information from you, all responses are literally uninformed guesses.

If DC, for the load current rating it is important to know what type of wall wart it is - switching or linear. For an old-stype linear type, the circuit probably is nothing more than a powerline transformer, a couple of diodes, and a capacitor. For this type, the output voltage rating is valid ***only*** when loaded to the rated output current. For lower currents, the output voltage can be significantly higher. I have a "3 V" part that makes 8 V under no load.

ak

 

There's an interesting design guide here:
http://www.hammondmfg.com/pdf/5c007.pdf

The standard filter is capacitive and it's also like a full wave rectifier.

For audio something limits the amp.
The load.
The supply rails.
The DC current available from the supply.
The amplifier output devices chosen.
The transformer core.