g540 and over-voltage

[draughted]

in my folly ive constructed a power supply using a torroidial transformer rated for 45v. turning it on ive found 66v at the capacitor. is this too much for my g540 with a max voltage of 50v.

and if, as it probably is, too much. can any one help with maybe a regulator circuit, as the torroidial put a hole in my wallet.

[kawazuki]

Originally Posted by draughted in my folly ive constructed a power supply using a torroidial transformer rated for 45v. turning it on ive found 66v at the capacitor. is this too much for my g540 with a max voltage of 50v. and if, as it probably is, too much. can any one help with maybe a regulator circuit, as the torroidial put a hole in my wallet.

What are the transformer spec's or a link to them would be useful? It suprised me a bit to get 45v out of a 30v tranny once rectified - works a beaut.

[draughted]

its a 500va wopper with two 5a 45v secondaries that ive wired in parrallel
i should have guessed, you know i built a 9v power supply last year and it turned out to be 12v, but i never thought it'd be out 20v

[Crevice Reamer]

DO NOT use this PS with the 50V MAX G450. Overvoltage is one of the few ways to kill it. Save it for a future machine or sell it on ebay. THIS $60 PSU will run most Nema 23 stepper motors with G540:

KL-350-48 48V/7.3A

http://kelinginc.net/SwitchingPowerSupply.html

CR.

[chuck1024]

A transformer with 45VAC secondard will make: 45 * 1.414 - 1.4 = 62 volts at the filter cap assuming nominal line voltage. Most transformers will make more voltage no load which is why you are seeing 66.

Putting 66 volts on the G540 is the kiss of death.

Personally I subscribe to the keep it simple approach and an unregulated supply is simple and adequate for driving steppers.

I am using a Antek 48V 500 watt power supply with my G540. I chose 500 watts because (3.5x4) * 2/3 is 9.2 amps which is very close to 500 watts.

It looks like they now only sell 47V 500 watt supply.

http://www.antekinc.com/ps.html

If you really want to make your own power supply you can buy nice transformers here too. I recommend a 34 or 35 volt secondard. I believe the 47volt PS uses a 34 volt secondary and the 48 volt PS uses a 35 volt secondary.

I am using keling tech KL23H276-28-4B motors and they work very well with the G540. I have the machine configured for 60IPM rapids. I can make them move 120 but I didn't test to see if they were loosing steps at that rate.

[Mariss Freimanis]

The G540 breakdown voltage is 68VDC. Your 66V supply is way too close to that number.

Mariss

[Al_The_Man]

Originally Posted by draughted can any one help with maybe a regulator circuit, as the torroidial put a hole in my wallet.

Usually it is very simple to reduce the turns on a Toroidal type, the secondary is normally wound last, the common ratio is about 2 turns/volt.
There has been many post here in the past on doing this, and it is much more efficient than external regulation circuitry.
Al.

[draughted]

no, i think that i would rather pay than fiddle with a transformer

[draughted]

on second thoughts will it affect the amp rating
and what is a turn exactly

[kcho]

Perhaps if you make a resistor and you put it in serial with the rectifier you could reduce the voltage in the bridge. There is too some high power varible resistor you could use for the test.

[Al_The_Man]

Originally Posted by draughted on second thoughts will it affect the amp rating and what is a turn exactly

The VA rating will stay the same, which means in theory if you lower the voltage by removing turns the current capacity goes up, but only to a point of the current capability of the secondary winding gauge.
If you carefully remove the outer insulation wrapping, this will expose the secondary wire winding, these are the wire turns referred to.
You just unwind the amount of turns that you need to reduce the secondary voltage by.
Reattach or solder the secondary flying lead conductor and rewind on the insulation tape previously removed.
It is a relatively simple procedure and cost virtually nothing except time.

If you want to find out the how many turns/volt the transformer has, you can wind on 5 or 10 turns of small gauge wire on top of the present taped winding, power up the transformer and measure the AC on this new winding, this will give you the ratio of turns per volt.
Al.

[steve323]

Originally Posted by kcho Perhaps if you make a resistor and you put it in serial with the rectifier you could reduce the voltage in the bridge. There is too some high power varible resistor you could use for the test.

A series resistor will only reduce the voltage when the full current is flowing through it. When the current drops, the voltage will be back to 66V.

Steve