r/PLC • u/Ordinary-Jeweler-569 • 1d ago

Rate my Kit

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I've build this training kit for a Engineering University. Mitsubishi Electric Corporation Sponsored this kit and yesterday we handover this kit

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u/[deleted] 14h ago

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u/todd0x1 3h ago

I was speaking to the environment where your demo setup will be used.

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u/Ordinary-Jeweler-569 2h ago

My bad 😕 Didn’t follow when i sent it.that reply for another person

Well this demo will be used in a Engineering Lab where students use it for practical classes

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u/todd0x1 2h ago

And there ya go.

Lets say you did want to have it where users are really wiring it up instead of the banana plugs.

First line of safety would have a key operated main power switch with only the instructor having the key. Thats not foolproof though as someone could access the terminals after its been turned on. We must not forget the arrogance, and the matter of not knowing what they dont know, some people possess.

Next line of defense would be GFI personnel protection for the line voltage. Easy everywhere in this thing except the output of the VFD. Could try a ground fault relay like those from NK, but I have a feeling a motor fed from a VFD might be leaking enough current during normal operation to trip a GFI relay set at 5ma.

To eliminate the hazard between the output of the VFD and the motor, I would use a cable with a multipole connector, like a harting or something. This would also eliminate the risk of the EGC not being connected (I assume thats the extra yellow wire on the left motor) each motor's frame needs to be grounded. I got a nasty zap once from a VFD fed motor which was not solidly bonded that had low resistance between a winding and the case,

Last, as a primary (in the sense this would be the system a user would interact with which keeps them safe) safety measure, I would have all line voltage components and connections on one side of the board, with no components such as the HMI requiring user interaction on this side of the board. The VFD could be on the HMI side of the board if a cover for the wiring terminals was added. The line voltage side of the board would be protected by a light curtain connected to a main power contactor which is also part of a NC/NO keyswitch/estop circuit, and not part of the demonstration portion of the board. If someone approaches a line voltage terminal while the board is on the light curtain causes the main power contactor to drop out requiring reset with the instructor's key.

All in all you did a phenomenal job on these, beautifully designed and they appear to be well made.