[theminor]

I'm looking for a good PSU to go with a G540 and ran across this: http://cgi.ebay.com/48-VDC-Power-Sup...-/220590300866

Lambda JWS480P-48 Power Supply. He says its a switcher power supply in the listing but I can't find any other data to support that. Then, it probably is regulated somehow. Anyway, 48 volts, 10 Amps with 20 amps max (for 10 seconds). It would be a great price, $40 shipped.

Would this be OK to use with a G540? I've read that switcher power supplies aren't the way to go...

I'll be driving (probably) 3 x 380 in-oz steppers...

If this will not work, any suggestions on a cheap power supply?

[Mariss Freimanis]

Almost all of our OEM clients (OK, customers) use switching power supplies. The parity or break even point between iron supplies (xformer, rectifier and bulk capacitor) and switchers was passed a few years ago. Almost everyone uses switchers now.

There are a few things to take into account when using switchers with motor drives. Switchers work at high frequencies (40kHz or higher) and have tiny output filter capacitors. Motor drives need big capacitors because a lot of energy moves between the drive and power supply.

You need to put 10,000uF on the switcher output VDC for step motor drives and at least 30,000uF if you are using servomotors. They form the very necessary "flywheels" on the source supply.

Avoid sophisticated supplies with overvoltage crowbar protection. The power supply "sees" more voltage on the output than it should and it shuts down. The voltage came from a regenerating drive (decelerating) and it fools a sophisticated power supply into thinking something is wrong.

If you use an overvoltage protected supply, decouple it with a rectifier diode going to your external 10,000uF or 30,000uF capacitor. This makes the even most persnickety switching power supply behave like a *****cat.

Mariss

[Mariss Freimanis]

Geezzz.... I really HATE automated nanny robot censors! Shame on anyone that uses these idiot robots. I typed p_u_s_s_y_c_a_t and the idiot automatic censor inserted a line of asterisks. The word p_u_s_s_y_c_a_t isn't vulgar and worse yet, I got it through just fine. I could have posted something truly vulgar this way.The word p_u_s_s_y_c_a_t means something that is of a benign or gentle nature.

It also leaves the impression I posted something vulgar that had to be ***** out. Idiot nannies! Is I***t next?

Mariss

[theminor]

Haha - I agree! What the **** **** ******* *******! :drowning:

Anyway, thanks very much for the thorough reply. It sounds like I could use that Lambda and add a couple of 5K+ uF capacitors to the output. I have no clue if that power supply has "overvoltage crowbar protection" or not - the data sheets I've read on it are not as thourough as I'd hope.

[japroach]

Their datasheet lists "overvoltage protection - yes", no idea if its crowbar. Diodes are cheap though.

http://us.tdk-lambda.com/lp/ftp/Specs/jws.pdf

[Pandinus]

I agree 100%... but I can save the filter and myself time...

@#$ 54 3#$ ^%$$% $% $%^ *&&^*@$%&&*6437 %^ %8 $%68 2 #$%& ^%#* 4% @$#7^7 ^%*$& *$%#^ 7#%^*

I typed that over twice as fast as normal, but its gonna take you a lot longer to read it

OK joking over, I have a question on the power supplies... I have a couple of linear power supplies rated at 40V, as soon as the g540 is turned on the voltage drops to anywhere from 38V-34V The 540 specifies 50V max, if I put a PC power supply in series, 12V (measures about 11.8V) that would be 46V to 50V working volts... So I was wondering how strict that rating is??? would 52 volts on startup kill it?? or should I wait till i redo my control case and PS using 4 PC supplies at 48 V (prob closer to 47)
To be honest the 540 seems to be pushing the motors fine at the 36ish volts... (Keling 387s) so I don't want to push it.

[Pandinus]

Oh, and this one has been asked a few times around... not sure if you've seen it or answered or if i missed the answer, but do the 540 outputs have flyback diodes built in for the relays, or should they be added??? I added some by default but your diagram didn't show any...

[Fastest1]

Oh, and this one has been asked a few times around... not sure if you've seen it or answered or if i missed the answer, but do the 540 outputs have flyback diodes built in for the relays, or should they be added??? I added some by default but your diagram didn't show any...

Is this to trigger a relay manually and eliminate the backfeeding of the G540?

[Pandinus]

No, when you energize an inductor ... relay coil or ignition coil for example, there is a magnetic field created. When the field collapses it creates a very high voltage spike that can damage semi-conductors. One solution is a reverse biased diode across the coil to absorb the spike. This is the flyback diode I was referring to.

[Fastest1]

No, when you energize an inductor ... relay coil or ignition coil for example, there is a magnetic field created. When the field collapses it creates a very high voltage spike that can damage semi-conductors. One solution is a reverse biased diode across the coil to absorb the spike. This is the flyback diode I was referring to.

Thanks

[theminor]

I agree 100%... but I can save the filter and myself time...

@#$ 54 3#$ ^%$$% $% $%^ *&&^*@$%&&*6437 %^ %8 $%68 2 #$%& ^%#* 4% @$#7^7 ^%*$& *$%#^ 7#%^*

Pandinus I've stared at your message and I just can't figure out how to decode it!

Did anyone ever determine whether flyback diodes are required when you connect a relay to either of the g540 outputs?

And one other question: if I hook up the large capacitor on the outputs of this power supply, do I need to worry about drain resisters for when the power is turned off? Or would these resistors already be present in the existing power supply? (And if they are present, would the larger capacitors harm them when the power is turned off and much more juice is drained through them?)