Thomas Compressor

[Al Skierkiewicz]

Oz,
I made the suggestion to try and diagnose the issue. If the PDP cannot handle the current then it cannot handle a CIM either. Connecting to the PDP through a 20 amp breaker for testing at least gives some electrical protection. We need to know where to look to suggest a fix.
Blocking the output port cannot not provide the necessary testing as it simply forces the piston to bypass compressed air. I would suspect that run current would only rise slightly in this condition. I am guessing that what is at issue here is a low voltage condition that is overheating the compressor armature.

[ozrien]

Originally Posted by Al Skierkiewicz

Oz,
I made the suggestion to try and diagnose the issue. If the PDP cannot handle the current then it cannot handle a CIM either. Connecting to the PDP through a 20 amp breaker for testing at least gives some electrical protection. We need to know where to look to suggest a fix.

Current is not the problem. That's not what the User's Guide suggests, and not what I posted.

My recommendation is find another way to direct-power the suspect compressor for the purpose of testing.

[Al Skierkiewicz]

Oz,
Can you describe how connecting the compressor through a Spike is any different than connecting the compressor directly to the PDP? The Spike is a relay with no other electronics in series with the load other than the breaker installed in the Spike.

[ozrien]

Originally Posted by Al Skierkiewicz

Oz,
Can you describe how connecting the compressor through a Spike is any different than connecting the compressor directly to the PDP? The Spike is a relay with no other electronics in series with the load other than the breaker installed in the Spike.

Just because a component is not in series doesn't mean it's not relevent. The Spike's catch diode is one example of this.

[Al Skierkiewicz]

Originally Posted by ozrien

The Spike's catch diode is one example of this.

???

[Mike Copioli]

Originally Posted by Al Skierkiewicz

???

Al,

The Spike has a suppression diode at the motor terminals. This diode clamps the inductive flyback that happens during both the freewheeling period and direction changes.

When a motor is connected directly to the PDP, the flyback that may occur during a breaker trip or simply from hot connecting the load may cause damage to the current sense IC's inside the PDP.

This is why we document this on more than one page in the user manual. CSA's and inspectors should be made aware of this. I would recommend that every inspector and CSA reads the documentation thoroughly.

[Al Skierkiewicz]

Mike,
As there is no rule that covers this, there is nothing on the inspection checklist for this item. I m not aware of any diodes on the motor output of the Spike, I believe there is an MOV, the same as the Victor. Is this what Oz is referring to?

[Mike Copioli]

Originally Posted by Al Skierkiewicz

Mike,
As there is no rule that covers this, there is nothing on the inspection checklist for this item. I m not aware of any diodes on the motor output of the Spike, I believe there is an MOV, the same as the Victor. Is this what Oz is referring to?

Al,

The Spike has a suppression diode at the motor terminals. This diode clamps the inductive flyback that happens during both the freewheeling period and direction changes.

When a motor is connected directly to the PDP, the flyback that may occur during a breaker trip or simply from hot connecting the load may cause damage to the current sense IC's inside the PDP.

This is why we document this on more than one page in the user manual. CSA's and inspectors should be made aware of this. I would recommend that every inspector and CSA reads the documentation thoroughly.

I have no better way to explain this.

[Richard Wallace]

Originally Posted by Mike Copioli

The Spike has a suppression diode at the motor terminals. This diode clamps the inductive flyback that happens during both the freewheeling period and direction changes.

Mike, thanks for the reference to PDP documentation -- it is well presented and definitely worth reading through by all interested FRC participants who work with the control system. Students, mentors, robot inspectors, CSAs, FTAs, etc. The new control system is a wonderful advance over what we've used before.

Since you have some detailed knowledge of the Spike relay that is not mentioned in its doc, can you tell us a little more about the suppression diode at its M+, M- terminals? I'd be interested in several of the specs for that diode, including leakage current, reverse voltage (clamping, avalanche, standoff, etc.), parasitic capacitance and inductance, energy ratings (single and repetitive), and anything else you know of that is pertinent to the protection it can offer against recovery voltage spikes produced when the Spike interrupts current to an inductive load. If those specs are not easily available to you, but you do have an example part to look at (outside of its case), can you tell us the manufacturer's part number of that suppression diode?

Thanks again for sharing detailed knowledge of FRC control system components.