From a maintenance technician's standpoint, the best defense is a spare encoder. It is easier to interchange encoders than it is to perform complex electronic evaluations. In other words, swag encoders now and ask questions later.

hat is servo motor overtemp?

Servo motor overtemp is obviously caused by excessive temprature in a servo motor. It can be sensed by an internal thermistor circuit within the motor windings or some form of external temperature sensor.

Servo motor overtemp is directly related to high current in one or more of the motor windings. There are few things to look for...

• Servo motor overtemp can be caused by breakdown of one or more motor windings


• Servo motor overtemp can be caused by excessive loading of the motor


• Servo motor overtemp can be caused by improper motor tuning, for instance, too much gain


• Overtemp alrams can also be caused by a faulty temperature sensing circuit (ie bad thermistor or thermocouple)

Here's my take on "What does no control volts mean?"

This alarm is exactly what it says...The control voltage is missing or was interrupted momentarily. This can be caused by many things, most of which can be identified with a voltmeter.

• The control's AC line voltage is absent or was briefly interrupted. You can't generate control voltages without an input voltage..


• Blown fuse or tripped circuit breaker either on the primary or secondary side of the power supply.


• Remember, there can be more than one control voltage in a system (ie 5v, 12v, 24v) so a "no control volts fault" can mean that only one of these is missing.


• The voltage signal that feeds the control voltage monitor is not present. This is the least common problem but can get you if you're not paying attention.

What does high DC bus mean?

As it states, the high DC bus error appears when the DC bus voltage is too high. This sometimes surfaces as an overvoltage fault (or overvoltage alarm). This can be caused by a few things.

• If the main DC bus voltage can be too high due to a power supply issue. This can be an internal power supply or an external supply that feeds a series of drives.


• The DC bus fault will also show up when there is an inadequately sized regenerative resistor (or wrong shunt resistor). This would be evident in the design phase of a project or after a mechanical modification was made to the equipment.


• The high DC bus alarm is also caused by an overload of the regen resistor due to excessive force when activating the regen circuit. This can be caused by stopping too fast or trying to stop too fast.

There may be other reasons for high DC bus errors but that is what I have seen.

What is a Maximum Lag error?

Here's my technical explanation of a maximum lag error, hope this helps you out, if anyone can add to this, please do...

Definition of Maximum Lag Error: Relating to a motion control system, the error is caused by the driven motor not being able to reach the commanded position within a set amount of time.

For the maintenance techs in the room...

A lag error can also be referred to as a "servo following error" depending on the software or hardware manufacturer. Anyway, from the standpoint of a maintenance technician, this usually means that the motor struggled to reach its desired position in time. This can be caused by a mechanical strain on the system and the motor falls behind on reaching its destination within the set time limit.

What should you do when you get a maximum lag error?

• Visually inspect the motor load for obvious causes of mechanical stress or strain.
• De-couple the motor from the load if possible, this will enable you to isolate the motion control system from the equipment it is driving. This step will usually uncover the issue.
• If the Maximum Lag error exists with the motor detached from the load, then there is a motor or feedback problem. Begin swapping known good components like encoder and motor if possible.

I have seen the problem being the driven axis or load being tight, like machine settings not done properly, and so on. When you uncouple the load, the problem usually becomes clear. It can still be a motor bearing or feedback problem also.

What is a servo following error?

A servo following error is one of the more common faults or alarms to rear their ugly head in a motion control system. I will try to explain a servo following error in two ways. First the technical definition, and then an explanation that would be more relevant to a maintenance technician or engineer. I'm not perfect so if anyone can add to this, please chime in.

For the engineers in the room...

Definition of Servo Following Error: Every control loop in a servo motion control system relies on position and velocity feedback to adjust its command signal. The feedback is read from either analog voltage fed back to the controller, or an encoder signal. This indicates the actual physical position of the motor.

The controller then compares the desired signal to the feedback signal. It instantly verifies that the motor is precisely following the controller's command. The difference between these values is called the "servo following error" (or simply following error).

For the maintenance techs in the room...

This can be caused by a few different things. If you are getting a servo following error on startup of a new system it can be a number of things.

• Encoder resolution is not correct, improper encoder, encoder wiring, or improper parameters related to pulses or counts.


• Command wires can be reverse polarity causing the motor to attempt a move in the wrong direction.


• PID loop is not tuned properly in the servo motor and drive combo. You would need to consult your manuals since each manufacturer has its own method of tuning.


• Following error setting is too precise. You would need to consult your controller manual as these procedures also vary among manufacturers.

OK, now for a system that has already been tested and successfully used for any period of time. We look at the causes of servo following errors due to component failure of a tested and previously operable system.

Remember, this error appears as a result of the motor not reaching its required position in the allowed time period.

• Check encoder connections, sometime wiggling the cable can cuase these errors to appear and disappear. Connection problems almost always appear in the connector or connector pins. The likely hood of broken wires within the cable are far less than the connection points, that is, unless you see a pinched or crushed cable.


• Bad encoder coupling is next in line. Encoder couplings can break or come loose causing slippage. This is easy to check.


• Bad encoder is next in line. Swap encoders with a known good one if you've got a spare, or interchange it with another available encoder.


• If the feedback doesn't seem to be the case. You would need to do a velocity loop test to verify the the motor and drive are functioning properly.

Velocity loop tests isolate the motor and drive from everything else. You would need to research the velocity loop test for your particular motor and drive combo. Hope that helps you. And if anyone can add to this, please feel free.

Quote from: travis on March 25, 2016, 04:26:AM
What is a Foldback Alarm?

Looking for a general explanation of a foldback alarm.

Foldback Alarm / Foldback Fault / Foldback Error or whatever you want to call it; it isn't actually an alarm in many cases. Foldback is designed into drives to protect them from overcurrent situations. When a foldback LED is lit on a drive it means that the foldback circuit has been activated due to current exceeding the rating of the drive.

When the drive senses to much current, it "folds back" some of it until the overcurrent situation has passed. It it never goes out, the overcurrent situation is still present.

Usually a drive will continue to operate during foldback, it is like a warning signal more than an alarm.

Looks like a little too much heat on the armature. Why didn't the thermistors warn the drive of the excessive heat. It seems like a motor that size should have adequate protection. Motor thermistors are there so that this doesn't happen. (so I thought)

The cheapest cube relays may not be the best cube relays. That's common sense, but I actually never payed much attention to the cube relay manufacturers in the past. I'm going to be a bit more aware of the brands and I'll try to post if I can come up with any real data.

My thoughts on programmable relays are that you get what you pay for. They are basically a simplified PLC with some limitations. I think if you are using them for very basic control circuits they would be fine.

As for Zen relay programming, I have never programmed one of these but it seems like it would just be a basic ladder style software. Does it come with a software package or do you have to go to Ormon's website and download it?

Re: How to upgrade from contactors to a drive ...

If you really analyze the upgrade process, I guess it comes down to research and cautious decision making. i think if you involve more than one drive specialist, you'll get some good ideas. You can use their quotes as guidance if you're making you own decisions on contactor upgrading.

Type S and Type SJ cord are the most common cord that I have worked with. The difference being the rated voltage and the overall cord diameter.

I understand your dilemma. Remote pot timers are not a common part for whatever reason. Years ago I had the same issue and if I remeber correctly, I ended up ordering an Eagle timer with a remote pot. What I remember most about this event was that there was a long lead time for the timer. The reason I remember that so well is because it taught me a lesson and i actually ordered a spare timer to sit on the shelf.

Re: Difference Between Flush and Projecting Proximity Switch

I think you just need to pull up the specs to see your answer here. The projecting proximity switches always have a greater sensing distance than the flush switches. As far as I know, that would be the only difference between flush and projecting switches.

Good question. Why not use capacitive proximity switches all the time? I would say because of the price in some cases. Capacitive switches have better range and are more versatile when it comes to sensing different materials, but what if you only wanted to sense ferrous metal in an environment where other material passed close enough to trigger the switch?

I think you would create confusion for the switch. I think this comes down entirely to your application because the difference in price shouldn't steer you from going capacitive.

I only use capacitive proximity switches to sense liquids. Other than that, I have mostly encountered inductive switches.

Bill,
Will they install a Rockwell drive without any additional charge? If so, then I'd go with Rockwell. Same goes if it were only a few dollars, otherwise why not leave the KB drive and retrofit someday if you have problems with the KB Electronics unit.

I don't have experience specifically with the KB drives, but chances are that it will last for some time. You always have the chance of a Rockwell drive failing too. So I would base your decision on initial cost.

Quote from: mallix on January 16, 2016, 04:22:AM
What is a Vickers EM-VT-24-10 board?

Hello, I was wondering what is the function of a Vickers EM-VT-24-10 board? I can't find any info on the card since it is an obsolete circuit board. The Part number is 682300.

How big is it? what is it supposed to do? Do you have any other info to add?

Quote from: mallix on January 16, 2016, 04:27:AM
What is a disposable relay?

Hello,
My colleague say he uses disposable relays but the phrase sounds bad. Are there disposable relays or is he referring to cube relays? thanks!

I've never heard anyone use the term disposable relay. From the sound of it, I would say he is referring to a relay that can easily changed out. Something like a cube relay...

Quote from: mallix on January 16, 2016, 04:30:AM
Hello,
Does anyone know how to repair a GE CR7CJ relay? Are there rebuild kits or contact kits available for the GE CR7 relays? or would these be considered throw-away relays?

I think repairing any relay depends on the cost of replacement, so whether a GE CR7CJ relay can be rebuilt or not would be based on parts availability. Some of these relays are designed to never come apart. If the relay doesn't have easy access screws for the contacts and coil, then it most likely wasn't designed to be repaired.

If there are no screws in the face of it, it would call it a throw-away relay.

Thanks, I ended up buying the exact same transformer and it works now. I never realized the output on these battery backups were square.

Re: How to upgrade from contactors to a drive ...

Also looking forward to a response to this. I'm also curious how a pro would go about upgrading logically. Anyone?

Alright, here's a question for those maintenance tech who dabble with PLC's for troubleshooting equipment...

What is the most maintenance friendly PLC?

I have some experience with the Allen Bradly line. I've used RSlogix 500 and 5000, so I like Allen Bradley PLC's for troubleshooting. What I'm looking for is some input from someone who has used different brands of PLC's for troubleshooting equipment. Are there more maintenance-friendly PLC's on the market?

What do you guys think?

Folks,
I have an industrial computer that shuts down immediately with battery backup. I installed an APC UPS on the computer to protect it from some recent brownouts, but it didn't work. I contacted my IT department and they gave me a different battery backup. When this one didn't work, we tried another brand all together but the computer still shuts down as soon as it moves to battery power.

This happens without even loading the power management software that comes with the UPS battery backup. So far I have tried an APC, a Tripp-Lite, and a Compu-power brand. Three entirely different units with the same result.

Has anyone ever seen this?

I was always under the impression that the motor nameplate was the key to the kingdom. If the motor says 400V than it has been designed for use at 400V. I would assume that you are safe at 10% max above that which would put you at 440V.

So 480V in a 400V motor, I feel like you would shorten its lifespan and possible increase its RPM. Anyone else have thoughts on this?

Quote from: worker1000 on September 22, 2015, 04:20:AM
Hello,
Since you guys are offering free advice, how do you test an obsolete DC motor?

How is this motor being started and controlled? SCR Control, contactors, or solid state drive?

I know analog multimeters take a little more effort than digital.

For some reason, I still feel more comfortable watching the needle deflect.

Good evening maintenance roundtable! My family calls me the 3rd shift guy since I have always worked 3rd shift jobs. looking forward to communicating maintenance issues and electronic questions with the group.

Hello guys,
I have a question regarding 480V contactor coils. I understand that wiring a control circuit with 480V is not acceptable for safety reasons, but there is the grandfather situation that I am confused with.

Are old 480V contactor coils grandfathered in? I need to replace a 480V coil (15D21G4) and I don't know if I have to rewire the controls or can I just buy another 480V coil.

Let me know your thoughts or if anyone knows that it definitely not an accepted practice to still use the 480V coils.

Thank you!