Servo Drive Repair

Well, in order to stand a chance of the forum helping, it might be an idea to state the make and model number of the drive equipment.

Some idea of where it is on the planet might also be an idea - just in case someone nearby has one available.

In the meantime, work-up a business proposal for changing this sort of drive out for something else a bit more current. Loss of product over a period of time would be the basis of the justification.

Sorry.

BUM63A-150/195-54-E-O-011

Baumuller is manufacturer

I've been away from molding for a long time.

Do you mean a VFD, perhaps?

Do you have the name of manufacturer and model #?

Well The drive has an incremental encoder so I figured that bumps it to servo status? it's a Baumuller, BUM63A-150/195-54-E-O-011. It's for the screw drive, I's a hydraulic press but the screw motor has a AC motor on it. If only the screw motor was hydraulic, I would have had this taken care of long ago...

The encoder is more than likely speed feed-back, since the radial position of the screw in the barrel is of no importance and the screw doesn't turn that much unless you are purging the machine.

Do you vary screw rotational speed often?

Screw speed never changes in our process, I have no idea why it would even need feedback on such a system. But it has it and it isn't working, I just can't stand sitting around waiting for 2 weeks for something if there is something I could be doing now to fix it.

Hook a VFD up and run with it. Depending on the gearing, you may not need any speed control.

But, I'm not there.

Good luck.

If only it was that easy, This is a medical plant so any change to our process requires our process engineers to run exstensive tests which would then have to be changed out once our replacement equipment comes in and then re-tested and theres no way they would allow this. I have to keep the process the same. I guess my main question remains why do I not have power on these bus bars on this drive? is there one main compoinent that can go bad to stop this. I have this pictured in my head as main power comeing in through some rectifier bridges and then being smoothed out with these capacitors, and this will be the DC bus that is used to make what ever wave it needs to make. The DC bus has no power so it must be something wrong with what makes this bus?

I know nothing about troubleshooting electronic controls, the members who have responded know lots about that.

I wonder if the screw speed is specified in your process control documentation?

Thank you, this is exactly what I was looking for, Still confused though. I have nothing on that DC bus. But I have power going to it. What are those lines going down off of the diodes? are they some type of control that could shut off all power to the bus?

Those aren't diodes in the 3-phase AC-line bridge, they're SCRs. That way the controller can turn the bus voltage on and off.

What about the 24V power to the controller? Also there appear to be some interlocks.

Yes, that SCR vs diode issue was established in post #15, and apologized for by me in #16.

A) I'm replacing the drive with a Baumuller, not replacing a Baumuller.

B) As this is not something I would normally be working on (In most cases we just replace and sent in for repair) I didn't want to pull this apart to work on it unless I knew what I was doing and what to look for, so I did some reading and asked a few question. As far as redesigning the system, We like to keep standard parts on equipment if possible, we have a few of these presses I'm sure we will stock this drive for next time it happens. I have no intentions of redesigning the system.

I don't believe the diodes have all vaporized, although I didn't take the drive apart to see them, I saw no signs, and I couldn't smell anything. Fortunately for me I normally set my meter in auto-volts (auto detect ac or dc) just by habit so I don't make mistakes (unless I'm working with small dc voltages). I measured voltage after the fuses and had voltage, and then on the bus and didn't have voltage. The 24 volt power supply is good, at least at the power supply. I could see a loose wire or something getting past me when I was looking at it.

Thank you for your reply, it was insightful.

You're right, I was apparently looking at the "62" version, which is just a diode bridge, the "63" is showing SCRs. So that's right, the firing board for the SCRs is apparently not working. That's the down side of using SCRs instead of a pre-charge resistor circuit.

Sorry for coming off a little snarky there, having a bad day with unqualified people being expected to work on my own drives. Sent a 250HP drive out to the field, contractor used an HVAC technician to hook it up, instead of an electrician. He put the line power leads on the load terminals and blew it up... claims we didn't mark it well enough. He said, and I am NOT making this up;

"The terminals on the motor said Line, so I connected those to the drive terminals that said Line. The terminals on the breaker said Load, so I connected them to the terminals on the VFD that said Load. You guys should be more clear about what I was supposed to do!"

This, by the way, is NOT the first time this has happened in my career! The other incident was 20+ years ago, also an HVAC technician...

So, whose rap is it?

Sounds like a a messy commercial situation now.

WHAT!!? YOU DID IT TWICE ??

Never mind, I'm on my third marriage .....

Aren't HVAC technicians classified as "Mechanical" for a reason?

Last incident was 20 Years ago? I see this same scenario more than twice a year.

The scary part for me is that many of today's technicians obviously do not even know when they are in over their heads and/or will not ask for help.

Maybe we all need to start issuing icons/pictures with the drawings and step by step instructions.

Aren't HVAC technicians classified as "Mechanical" for a reason?

In numerous states, mechanical equipment technicians and millwrights are allowed to make electrical connections to their associated equipment. I think those rules were put in place to avoid having to bring in an electrician to connect the 24V wires for a damper operator, but unfortunately a lot of general contractors take advantage of the vagueness of it to have them do things they are totally unqualified to do. Frustrates the heck out of me.

Yep, not only frustrating but also heart wrenching.

We have had two technicians in the last four years that have died from their own electrical mistakes and one that died from someone else's.

This should not be happening to anyone and I personnaly think it should be criminal to only give a technician two years of formal training and expect them to survive on their own.

Rant over but not forgotten.

"Maybe we all need to start issuing icons/pictures with the drawings and step by step instructions."

Seems a lot easier than replacing the equipment for an unhappy customer....jus sayin'

Besides, icons and pictures will do nothing to thin the gene pool.

We've had our fair share of servo drive failures. I'd say 80% of the time, it's been bad capacitors, but I've never torn one apart. And that probably doesn't help a whole lot, but if it's going to get scrapped, why not tear into it anyway and possibly learn something? Best of luck!

It's something to think about though, if 80% of the time it's the capacitors, and this time it turns out to be a controller, how much life is left in those capacitors? This is a used and fairly old drive. If I put money into this drive to repair it I want to know it's not going to go down again next year. I guess it becomes more of an issue of balancing cost and labor with cost of down time. Then it's a matter of how much faith I have that I can even fix. If I do think this is a board, that I could potentially buy and replace, can I prove that before I buy it? I have a few idea's of how I might go about checking this but I'd love to hear some thoughts by more experienced people.

Ac servo drives are complicated devices, some using hard wired logic, some using software control. If you intend to service this drive, you should check with the manufacturer and see if a class on repair is offered...probably not economical for one drive repair. Manufacturers usually have tech manuals for qualified repair sites, that show board test points and voltages AND frequency/wave forms at test points. It is imperative you have this information or you'll probably do damage.

Tech manuals you say. I like the sound of that. My department wouldn't send me anywhere for training but they would definitely buy me a tech manual. I wonder if I could get a manual like this without taking there class.

Many manufacturers will supply a tech manual free of charge.

Asking for one is free....