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Strange Geo Amplifier Faults
#1
We are having trouble with amplifier faults using a PMAC2 and a GPL201 amplifier. We get occasional (every minute or so) amplifier faults back at the PMAC2 board, but they don't appear to be coming from the amplifier.

There is no fault code on the amplifier, and we can get around this problem by disabling the amplifier fault checking in Ix25. Of course, this leaves us without an amplifier fault input.

Has anyone seen this behavior before? This is a seven axis system, so we have been able to swap around the cabling, Acc8 boards, etc. The problem always seems to follow the GPL201 amplifier. (Note: The other amplifiers in the system are GPL052 and GPL102s. They do not have this problem.)

Thanks,

Matthew Dean
Coastal Controls


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#2
We fixed the problem by replacing the GPL201 amplifier with a different one. It looks like the original GPL201 was DOA. I'll post an update with details once we get it repaired.

Matthew Dean
Coastal Controls
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#3
DT Support,

The GPL201 was fixed under warranty. The paperwork says "replaced C160".

Now, we have ordered a new batch of GPL amplifiers for a different job and are having the same problem again. This time on a GPL102 amplifier. Should we send it back for repair as well?

Thanks,

Matthew Dean
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#4
(12-10-2012, 09:29 AM)MatthewDean Wrote: DT Support,

The GPL201 was fixed under warranty. The paperwork says "replaced C160".

Now, we have ordered a new batch of GPL amplifiers for a different job and are having the same problem again. This time on a GPL102 amplifier. Should we send it back for repair as well?

Thanks,

Matthew Dean

Matthew,

Can you please give us the RMA number on the previous unit which was repaired?
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
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#5
Sina,

The original RMA was 9001-00586, and the repair information was "REPLACED C160 AND TESTED OKAY"

Thanks,

Matthew Dean
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#6
Hi, Matthew

Can you also give us the serial number of that GPL102 amplifier so we can cross reference if there is anything wrong with the C160 component?

[quote='Sina' pid='4380' dateline='1355290907']
[quote='MatthewDean' pid='4377' dateline='1355156954']
DT Support,

The GPL201 was fixed under warranty. The paperwork says "replaced C160".

Now, we have ordered a new batch of GPL amplifiers for a different job and are having the same problem again. This time on a GPL102 amplifier. Should we send it back for repair as well?

Thanks,

Matthew Dean
Reply
#7
JayL,

We are having trouble with GPL102, Serial Number: C000B76T.

Thanks,

Matthew Dean
Coastal Controls
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#8
Delta Tau,

More of the same. We had an amplifier repaired by Delta-Tau and verified as OK. As soon as the customer put it into service, he got the mysterious amplifier fault again. Apparently the factory testing doesn't check for this problem. Is there anything that we can do for this? It seems like a problem that has been around for several years now.

Thanks,

Matthew Dean
Coastal Controls
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#9
The factory tests each amplifier individually before leaving the plant. Board level testing includes visual inspection and automated in-circuit board testing. Top level assembly includes open loop (heat chamber) burn-in and closed loop (running motors) functionality, I/O and other inputs outputs.

C160 is related to the gate driver circuitry. This could be a grounding issue, but also power-up procedure / soft start:
Typically, you want to make sure that the controller is turned on before the drive. This ensures that the ADC clock is ready for the drive to sync into when it comes up.
You want to make sure that logic power is always turned on before main AC.
you want to make sure that the main AC is never recycled repeatedly and rapidly. The caps must discharge (at least partially, roughly about 5 minutes) before cycling main AC.

Blowing a cap on the gate driver side may still allow the unit the function.

- Is this always on the same axis, panel location? excessive EMI noise?
- What is the main AC power coming in, and is there any filtering on that? (e.g. EMI, voltage suppressors etc...)
- If you run this axis alone (all other motors Killed), would you still get a fault?
- Have you tried Enhanced mode to see if there are faults on the ADC A (lower 12 bits) of the axis in question
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#10
Richard,

This problem seems to occurs on about 1/3 of the GPL201 units that we install.

We have had this happen at four separate facilities. They were all on multi-axis machines, so we were able to swap the amplifiers around. The problem always stays with the amplifier. Also, replacing the amplifier always fixes the problem.

One thing that we have noticed is that when the motors are sitting still (although still enabled and closed-loop) we don't get the errors. They only show up when there is a decent amount of power going into the amplifiers. Do you know how much current you use during your closed-loop testing at the factory?

Thanks,

Matthew Dean
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#11
If we are suspecting EMI noise then closed loop and open loop should exhibit similar symptoms for a given amount of current.

In closed loop, I don't think we push too hard. We just want to make sure that the encoder circuitry is functional.

In open loop, I believe that we run a 24-hour cycle of continuous current drain interrupted by certain peaks for a calculated amount of time (without tripping).

Is the 24V logic power supply common to all drives? and do you bring the wires from the drives back to the main terminals of the power supply?
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