Will A Gecko 320X drive these?

[Jackal66]

Hello,

My mill is:

Hurco KM3P knee mill. Servo motors are 90VDC, 12 Amp continuous, 20 A peak.

Will the Gecko 320x drive these?

Also I need a new power supply. Mine is putting out 92 VDC, through the rectifier. Can I run 80 Volts DC through the Geckos, or should it be a little lower?

Need a recommendation for the power supply, or preferably just a transformer supplier.

Thanks,
JAckal

[morestuff]

Yes, the G320X will drive these motors.

The G320X is limited to 80 volts, so you will
need to get your power supply down to 80 volts
or less. I usually recommend 72 volts or less
to allow for 10% power line fluctuations.

Lower voltage maps directly 1:1 to lower top
end speed, but your original machine likely did
not use 90 volts to drive the servos. Running
them a 72 volts will result in a close enough to
the original performance for most purposes.

Lower voltage has minimal effect on maximum
torque and acceleration.

Regards,
Steve Stallings
www.PMDX.com

[Jackal66]

Thanks Steve,

I appreciate the reply with good information. There were a lot of views but no one answered yet.

I'm still knocking around my decision. The availability of the Geckos means a lot.

Sometimes other brands are sold out, and you have to wait...........................................................................

Warranty or not, it is nice being able to get another drive within 24 hours.

Do you have a recommendation for a transformer?

Thanks,
JAckal

[morestuff]

For good prices on reasonably good transformers,
it is hard to beat Antek. http://www.antekinc.com/

Remember that the DC voltage from a bridge rectifier
will be approximately 1.4 times the nominal AC input
voltage.

The AN-10450 or AN-15450 transformers would be
suitable, with the former be OK for most users and
the latter if the machine was expected to run under
full load most of the time.

Regards,
Steve Stallings
www.PMDX.com

[Jackal66]

Steve,

I see that they show voltage rating under load .

I don't know how they load them down, but my transformer says 60 volts AC & calculated it to be 84.84DC with a bridge rectifier.

When I checked it last week ( No Load ) the transformer was putting out around 64.9 volts AC.

That comes to around 92VDC through the caps.

This is what made me re-think my servo drive selection.

They would probably load test it similar to the method used in checking an automotive battery under load.

How much difference is there in Load VS. Non-load ratings?

Some sort-of "Rule of thumb"?

Thanks,
JAckal

[Al_The_Man]

Have you looked at taking turns off? Toroidals are easiest but EI laminated can be done, I have done a few in my time.
For toriods it works out to around 2turns/v, square laminated it could run to 3 or 4.
No need to recalculate the VA requirements either!
Al.

[Jackal66]

Al,

This one is laminated. I wondered the other day if you could remove windings on it.

If my original plan falls through and I end up with a lower voltage drive, I will try to unwrap a few coils on this one.

It will be no use to me if my drives are 80V.

I'll let you guys know what happens in a day or 2.

Thanks for the info,

JAckal

[morestuff]

The amount that the loaded voltage drops below
the unloaded voltage will depend on the amount
of load, the source impedance of the transformer,
and the amount of filter capacitance. Relying on
the loaded voltage being lower is not a good idea
because it could become higher when motors are
at rest, or even worse, slowing down with the
mass of the machine trying to keep them moving.
This results in the motor generating a voltage
(back EMF) that sends current back in to the power
supply unless your drivers have provision for
braking resistors. This is primarily an issue with
servo motors, and can cause the supply voltage
to rise above even the unloaded voltage in some
cases. Most of the time when one motor is returning
current, there are other motors that are not slowing
down and they will consume it, so the voltage will
not rise above the normal peak supply voltage of
the power supply, but it can happen.

Regards,
Steve Stallings
www.PMDX.com

[Jackal66]

My mill has the EMF capacitors on it from the factory. Could they be dried out and need replacing?

Here is a link where I asked about them:

http://www.cnczone.com/forums/hurco/...citors_my.html


And another link where Al_the_man gives me more info about them.



http://www.cnczone.com/forums/genera...my_servos.html

When the transformer comes out, I'll post some pics before working on it.


Thanks,


JAckal

[Al_The_Man]

Originally Posted by Jackal66 My mill has the EMF capacitors on it from the factory. Could they be dried out and need replacing? JAckal

Very rare for these type to dry out, which is usually a symptom seen on electrolytic types, the ones usually used here are hermetically sealed paper, so there is really nothing to dry out.
An extreme failure could be caused by a very large spike puncturing the insulation, in this case they usually go short circuit.
The resistor in series is supposed to prevent this however.
Al.

[Jackal66]

Al,

That is good to know.

Later today, I'll get the transformer out and take look at it, plus post some pics.

Thanks for all of the help,

JAckal

[mikeysformula]

I use them on mine.. I have the stock tranformer and I just pulled one winding at a time until I had 80 volts..