How Tolorant are Server PSUs about High Current Pulsed Loads?

[iamdarkyoshi]

So my 3D printer uses this REALLY old server PSU as a power supply. 

I have not had any issues with it. However, I want to avoid future issues. My printer PWMs the heating elements at a low frequency, only a couple hertz. This is to avoid any high pitched whine that would come from a high (but audiable) PWM frequency.

 

I have already mounted a heatsink to the side (where most of the heat is generated)

 

But this printer pulls quite a bit of power.

 

I know 200w or so is going through the chamber heater constantly without pulsing, but the other 140w is being pulsed on and off, which would present quite a nasty load to the power supply.

 

How tolorable are supplies like these at supplying power to nasty loads like this?

[daniellearmouth]

I would assume server grade stuff would be able to tolerate it just fine. After all, server grade hardware is intended to operate 24/7 and not fail at all if possible.

[lowlyf]

Pumping inrush current like that over and over may cause issues. It really depends on how well the caps in the supply handle being loaded over and over again. If it's overheating, it will die, sooner than later. I'd look for an application specific supply. How many hz are the 140 watt pulses? 140 isn't much, just depends on the hz.

[lowlyf]

You'll know when the current/Hertz is too great when voltage starts to droop.

[iamdarkyoshi]

1 minute ago, lowlyf said:

Pumping inrush current like that over and over may cause issues. It really depends on how well the caps in the supply handle being loaded over and over again. If it's overheating, it will die, sooner than later. I'd look for an application specific supply. How many hz are the 140 watt pulses? 140 isn't much, just depends on the hz.

Only a couple hertz. The supply is well within its safety margin, and it is basically cold. I might add an inductive filter and capacitor bank for it, as this supply came from a really friggin old server, I am amazed to see it still works

[lowlyf]

Thats a good idea. Another thing is to get some circuit protection inline on the DC side. I've seen old PSU run through shorts and run till the caps blew and the whole thing caught fire. They have a lot of potential energy, and sometimes not the best circuit protection.

[iamdarkyoshi]

4 hours ago, lowlyf said:

Thats a good idea. Another thing is to get some circuit protection inline on the DC side. I've seen old PSU run through shorts and run till the caps blew and the whole thing caught fire. They have a lot of potential energy, and sometimes not the best circuit protection.

I am sure this one would shutdown safely if it shorted out. Apparently you can still buy them for a pretty hefty price on amazon: http://www.amazon.com/DPS-600CB-Redundant-Power-Supply-230822-001/dp/B00DUGDQY8

 

I have no idea where my other one went

 

But this one has been through a lot, mainly previously used as a hobby charger supply.

[Stefan1024]

As you draw 200 watts constantly, it's only a 70% increase in load. It should ebe able to handle that.

If you like you can add some capasitors to the rail (1 - 20 mF). But place them close to the heater. To much capacity to close to the PSU can mess up the regulator if you are unlucky.

 

Why don't you use a PWM > 30kHz?

[iamdarkyoshi]

1 minute ago, Stefan1024 said:

As you draw 200 watts constantly, it's only a 70% increase in load. It should ebe able to handle that.

If you like you can add some capasitors to the rail (1 - 20 mF). But place them close to the heater. To much capacity to close to the PSU can mess up the regulator if you are unlucky.

 

Why don't you use a PWM > 30kHz?

Pretty sure that would be very difficult to do with the current setup. The controller is basically an arduino

[Stefan1024]

Just now, iamdarkyoshi said:

Pretty sure that would be very difficult to do with the current setup. The controller is basically an arduino

They have a dedicated hardware modul (timer) to create a PWM. You can write the duty cycle into a register and everything else is done by the module. You can even set the CPU to sleep and it's still working.

[iamdarkyoshi]

1 minute ago, Stefan1024 said:

They have a dedicated hardware modul (timer) to create a PWM. You can write the duty cycle into a register and everything else is done by the module. You can even set the CPU to sleep and it's still working.

I am really not sure how easy that would be in the marlin firmware

 

I am not particularly great at software and coding...

[Stefan1024]

Just now, iamdarkyoshi said:

I am really not sure how easy that would be in the marlin firmware

 

I am not particularly great at software and coding...

I haven't worked with this software so far so I can't help you sorry.

But I do a lot of programming in C and evertime we need a PWM we use the HW modules. But when you got the system running by doing it in software than I won't change it.