blowing electrontics

[markct]

anybody have any thoughts on why i would be replacing:
2- z axis amps, z axis motor and a vector drive all within the last 2 years?
is this normal for a 1997 vf4?
shouldn't the z axis fuse protect the amp boards????

[gar]

070622-2016 EST USA

markct:

Not normal.

All the servos and the spindle use the same high voltage power supply, about 325 V, in the vector spindle drive for both the spindle and servo system. I do not believe there were any particular quality problems for machines of that age.

.

[HuFlungDung]

Possibly the transformer taps (in the Haas) were not correctly set and your power company is providing power a bit higher voltage than would be optimum? The inverter provides the power for the servos. Maybe it is a case of the weakest link in the chain will fail eventually from the stress of too high voltage.

[Geof]

I think you probably have incoming voltage problems. Has anyone ever told you about changing the transformer taps at the bottom of the control cabinet to match your incoming line voltage and keep the DC bus between 320 and 340 volts.

The Haas tech who services my machines has stressed that going outside these limits is risky and can damage things. He said running too high can lead to overheat alarms and running too low can prematurely fry the elctronics.

You can see the DC bus voltage on the Diagnostics screen if you page down once (I think). Check it at different times of the day; your incoming voltage may fluctuate depending on the time of day.

[serviceman]

the early haas amps rev f where really weak and so where the earlier vector drives if the vector drive has a bar under the screw terminals where you have to put a screwdriver through the slot to get to the screws then it was garbage and bound to fail the older vector drives blew when you smoked an amp the newer ones alarm out when they sense a short.

[markct]

thanks for the ideas. the transformer taps where checked and i just checked them again. shouldn't the z axis fuse protection fault out before the amp blows. i'm concerned that i shouldn't put another amp in if that isn't working.

[Al_The_Man]

I am not familiar with this exact machine, but If you have the taps set for the incoming service value and it is right on the edge, it may pay to up the tap one to the next highest if it is in low increments.
Also fitting semiconductor fusing, may offer better protection, if not already used.
Al.

[markct]

i'm not familar with semi-conductor fusing?

[Al_The_Man]

Originally Posted by markct i'm not familar with semi-conductor fusing?

They are the same physical size fuse , but very fast blow, designed to protect solid state circuitry.
Al.

[gar]

070623-1527 EST USA

markct:

Have you measured your DC bus voltage? What is it?
Have you put a voltmeter on the DC bus and monitored it over time? It will vary as a function of spindle and servo loads, and will rise under heaay dynamic braking. High deceleration and inertia load pumps energy back to the DC bus capacitors. Does your regen resistor, dynamic braking, function and limit the peak DC bus voltage? Does the regen resistor get excessivly hot, should cause an alarm if so, or does it never get hot at all?

How stable is your AC supply voltage and is there good balance? Do you encounter large line transients? Are all your cooling fans working? Is your room ambient temperature high? Do you run at 100% load on the spindle most of the time? Very often at 150% or 200%?

Our vector drive machines range from 1996 thru 2000 and we have had no failures in this area, and few failures at all.

A spindle motor that is not overloaded should be very reliable. However, the failure of a motor driver could damage its motor.

Al:

Specifically what is "semiconductor fusing"? Are you referring to very fast thermal fuses, or some kind of semiconductor device used as a fuse? (edit) You responded while I was composing my question. (end edit)

..

[Al_The_Man]

Originally Posted by gar Al: Specifically what is "semiconductor fusing"? Are you referring to very fast thermal fuses, or some kind of semiconductor device used as a fuse? (edit) You responded while I was composing my question. (end edit) ..

Gar
Semiconductor fuses or Rectifier fuses as some manufacturers call them, are designed to protect solid state circuitry, typically SCR/PWM drives etc, they typically have very fast sweep-out rates and have no time delay element.
Most of the fuse manuf. offer them, Ferraz-Shawmut for e.g.
http://us.ferrazshawmut.com/oem/reso...ATIONS2_44.pdf
Al.

[serviceman]

the newer amps hold up better than the older ones the fuses are replaceable and you can check the amps after replacing the fuse to see if you can put it back in service after replacing the fuse do a diode test on the amp between +hv and - hv and check it against a known good amp with no wires attached to either one