Generate 24v 20ish amps from a wall socket?

Papabravo

Joined Feb 24, 2006
13,728
Is there any way to generate 24v 16-20 amps from a wall socket, besides a massive transformer?
Where is the wall socket, and would you mind defining massive for us.

The power output you require is 24V * 20 Amperes, which is 480 watts. If we assume that your transformer is 60% efficient, that will require 800 watts from the wall plug. At 120 VAC(rms) that would be approximately 6.5 Amperes. This is well within the capability of US household service. At 240 VAC(rms) that would be 3.33 Amperes, again within the capabilities of household service.

There is no safe way to do it without a transformer, and I don't accept your characterization of the required transformer as massive without more information which you failed to provide.
 
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Papabravo

Joined Feb 24, 2006
13,728
Yes. A switch mode power supply.
Which might still require a transformer albeit, a smaller one due to the presumably higher switching frequency. 800 watts is still a pretty hefty power level, for a first project in this realm. Maybe somebody has a ready-to-go design in their hip-pocket.
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
Where is the wall socket, and would you mind defining massive for us.

The power output you requires is 24V * 20 Amperes, which is 480 watts. If we assume that you transformer is 60% efficient, the will require 800 watts from the wall plug. At 120 VAC(rms) that would be approximately 6.5 Amperes. This is well within the capability of US household service. At 240 VAC(rms) that would be 3.33 Amperes, again within the capabilities of household service.

There is no safe way to do it without a transformer, and I don't accept your characterization of the required transformer as massive without more information which you failed to provide.
Massive as in bigger than anything I have. Unless I’m mistaken the bigger the transformer, the more amps can be drawn, correct? Also the wall socket would be a standard 120vac.
 

dendad

Joined Feb 20, 2016
3,528
A bit depends on your definition of "transformer" too. If you are referring to the 50/60hz transformer in the power supply, then switch mode will be a lot smaller. They do still include a transformer and as @Papabravo mentions above, you will require a transformer of some sort.

An example is...
https://www.amazon.com/Switching-(SMPS)Monitoring-Industrial-Transformer-220VAC-DC24V/dp/B0786LMNR2/ref=sr_1_2?dchild=1&keywords=24V+20A+power+supply&qid=1588808441&sr=8-2
It is 8.46 x 4.53 x 1.97 inches so does that fall below your "massive" measurements?
As to the quality of this one, I have no idea.
Other wise, Meanwell is a respected brand, but they will cost more.
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
A bit depends on your definition of "transformer" too. If you are referring to the 50/60hz transformer in the power supply, then switch mode will be a lot smaller. They do still include a transformer and as @Papabravo mentions above, you will require a transformer of some sort.

An example is...
https://www.amazon.com/Switching-(SMPS)Monitoring-Industrial-Transformer-220VAC-DC24V/dp/B0786LMNR2/ref=sr_1_2?dchild=1&keywords=24V+20A+power+supply&qid=1588808441&sr=8-2
It is 8.46 x 4.53 x 1.97 inches so does that fall below your "massive" measurements?
As to the quality of this one, I have no idea.
Other wise, Meanwell is a respected brand, but they will cost more.
Great, thanks for the help. Size isn’t a problem, shouldn’t have said massive transformer. My choice of words was poor
 

Papabravo

Joined Feb 24, 2006
13,728
Massive as in bigger than anything I have. Unless I’m mistaken the bigger the transformer, the more amps can be drawn, correct? Also the wall socket would be a standard 120vac.
Not necessarily. I don't know what you have, but this project is not doable with stuff you might just have laying around under any circumstances I can imagine. I believe there is a reasonable solution that would be safe and cost effective.

EDIT: and it looks like you found an off the shelf solution.

BTW: There have been many developments in transformer design since the days of tube televisions with those iron core monsters. Not the least of which is exotic core materials.
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
Not necessarily. I don't know what you have, but this project is not doable with stuff you might just have laying around under any circumstances I can imagine. I believe there is a reasonable solution that would be safe and cost effective.
Yes, the switch mode power supply seems very promising
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
If you do probing or experimenting on this with an open chassis, observe the usual safety precautions. I'd really hate for you to be nominate for a Darwin Award.
Yeah, they make them in the exact specs I need so hopefully won’t be electrocuting myself by playing around
 

Papabravo

Joined Feb 24, 2006
13,728
Yeah, they make them in the exact specs I need so hopefully won’t be electrocuting myself by playing around
Looks like input and output wires are all terminated along the one end. If I was you I would use crimp on lugs for the screw terminals to avoid exposed wires.
I don't suppose you have a spare NEMA cabinet around....nah - didn't think so.

https://www.nemaenclosures.com/custom-enclosures.html

Good Luck
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
Looks like input and output wires are all terminated along the one end. If I was you I would use crimp on lugs for the screw terminals to avoid exposed wires.
I don't suppose you have a spare NEMA cabinet around....nah - didn't think so.

https://www.nemaenclosures.com/custom-enclosures.html

Good Luck
Thanks, will do. Electrocuting myself is my least favorite thing to do beside dying from electrocution.
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
If you need 20Amps, go with a 25Amp or larger unit. It will last a lot longer with a bit of headroom.
Got it, I’m using it for an electric scooter motor to power a lathe, so I’m not sure I’ll be needing the full amps. The motor says 16.6 amps, so if I’m using it for a lathe to turn metals, mostly aluminum and silver (nothing too fancy or super hard) how many amps would it draw? I know it’s hard to pinpoint but I assume it’ll be less than the full amps it requires. From what I know the bigger the load the more amps it draws, so I assume it’ll draw less then 16.6 amps
 

Papabravo

Joined Feb 24, 2006
13,728
Got it, I’m using it for an electric scooter motor to power a lathe, so I’m not sure I’ll be needing the full amps. The motor says 16.6 amps, so if I’m using it for a lathe to turn metals, mostly aluminum and silver (nothing too fancy or super hard) how many amps would it draw? I know it’s hard to pinpoint but I assume it’ll be less than the full amps it requires. From what I know the bigger the load the more amps it draws, so I assume it’ll draw less then 16.6 amps
Good that you asked. As you may or may not be aware motors will vary greatly in how much current they require to run continuously, and how much they require to start from from 0 rpm. The same considerations apply when there is a load transient where the change in load causes the motor to slow down or stall (stop). Without knowing the details it is hard to speculate on what the situation might be. You can do some experimentation to answer these questions.

What I can tell you from long experience is that a given SMPS (Switched Mode Power Supply) may or may not react well to a load transient. The ones that behaved poorly would drop their output voltage on startup or on a load transient which would also increase the current demanded. This was because the early designs could not compensate fast enough to prevent that. Modern designs should do a better job, but you need to get a better handle on what your motor requirements are at startup. Having some headroom on your supply is a really good idea. Will it be enough? Be driven by the data.
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
87
Good that you asked. As you may or may not be aware motors will vary greatly in how much current they require to run continuously, and how much they require to start from from 0 rpm. The same considerations apply when there is a load transient where the change in load causes the motor to slow down or stall (stop). Without knowing the details it is hard to speculate on what the situation might be. You can do some experimentation to answer these questions.

What I can tell you from long experience is that a given SMPS (Switched Mode Power Supply) may or may not react well to a load transient. The ones that behaved poorly would drop their output voltage on startup or on a load transient which would also increase the current demanded. This was because the early designs could not compensate fast enough to prevent that. Modern designs should do a better job, but you need to get a better handle on what your motor requirements are at startup. Having some headroom on your supply is a really good idea. Will it be enough? Be driven by the data.
Cool, got it. I’ll do some research and definitely give myself some headroom, maybe get in contact with the original owner of the motor see if I can figure out the company or anything. It has very little markings on it. I posted a thread asking questions about it a little bit ago, so if you could take a look maybe you could derive some knowledge. I’m 90% sure he used it for an electric scooter, since it’s similar to other electric scooter motors.
 
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