Can someone explain the Armature Output Waveform from a Parker 514C Controller?

Well, we know it isn't a servo motor since "servo motor" meant "hydraulic motor" in 1942.  However, I agree that the insulation might be weak by modern standards.  In a lot of cases, motors that old have actually been rewound once or twice (or more) and are now up to modern insulation standards.  Are you replacing an existing DC drive or was this literally a motor-generator rig?  Or is this a lathe that came off a warship with DC power?

Well, we know it isn't a servo motor since "servo motor" meant "hydraulic motor" in 1942.  However, I agree that the insulation might be weak by modern standards.  In a lot of cases, motors that old have actually been rewound once or twice (or more) and are now up to modern insulation standards.  Are you replacing an existing DC drive or was this literally a motor-generator rig?  Or is this a lathe that came off a warship with DC power?

I'm replacing a motor-generator setup.  The original DC control panel was missing some critical parts that are no longer readily available and I'm not sure if the motor-generator itself was functional, so I figured this would be a good upgrade. The DC motor is in good shape and runs well with the 514C, but I'm just testing / tuning it at the moment.  Now I'm concerned about running it long term due to the armature wire insulation issue.

Hmm.  There are some unknowns here.  If the motors has been rewound in the last 30 years, the company that did the rewind probably used magnet wire designed to stand up to DC drives.  If the motor was rewound prior to that (or has never been rewound), then we might have an issue.

One thing you could try is a megohmeter.  If you put a meg on the armature and use it to check insulation resistance to the frame (make sure to disconnect the motor from the drive when you do this), it should show you resistance.  On a modern good motor, the reading should be in the range of 10 MΩ to 3 GΩ or possibly even higher.  Under 2 MΩ is a definite red flag.

Now, that's not a bulletproof test because the motor could technically have high insulation resistance and a relatively low temp rating, but it's the closest test we can get I think.  If the meg test goes well, most likely you have magnet wire that will work okay with a drive.

Otherwise, you need to get the motor rewound.  A rewind is a good idea every 20-30 years anyway.  There are companies out there that rewind motors as a service.

Daniel,

Take a look at this trace from my 514C.  It shows one leg on my 245V AC input in yellow and the positive output for the armature of the 514C in purple.  It looks like I might have a failure in one or more of the SCR's on the board.  Notice how the armature output follows the input voltage precisely for 1/4 of the input AC waveform just after the peak until the zero crossing.

Do you have an example trace for a properly functioning 514C you could share with me?  Does the 514C have fault codes I can look for?

This does not look like a malfunctioning waveform.  Please refer to the Wikipedia link I provided as it has an animation that shows SCR output waveforms.  This is about what I expect if you are putting a meter right on the output of the drive.  The SCR turns on part-way through the AC waveform and stays on until the zero crossing.  After that, the motor's DC voltage takes over.  This is the voltage generated simply by the motor spinning with the field turned on.