Ready Steady Eddy

[Jonathan]

Removing power to the inverter via a contactor is the obvious emergency stop strategy and it could be said that removing power from the inverter under load will damage it, that might be true but better to have a damaged inverter than a damaged limb.

Unlikely to cause significant damage to your limbs due to spindle's low inertia, so personally I'd rather it damaged the limb as that'll get fixed for free on the NHS, unlike the VFD.

Why would the inverter be damaged in this situation? Is it because once the power is cut to the inverter the spindle acts as a generator and this generated current can damage the inverter?

Vaguely.

Just noticed my Huanyang vfd has terminals to add a braking resistor. If power is removed from the inverter would this still be used/effective? would it cause damage to the inverter?

If you remove the power, the inverter can't do anything as it will only remain switched on for less than 1/10th of a second before the capacitors discharge. So no, it wont apply the brake.

I would like to have a safety system that does not compromise at all on safety but has the best chance on leaving the equipment undamaged

In that case you need to separate 'fault conditions' from safety concerns - e.g hitting a limit switch or stepper driver fault signals do not pose safety hazards, so treat them as such and wire it so the machine just pauses. The only one that warrants fast and complete shutdown is pressing the e-stop, as that's what you can supposedly do if you're about to get hurt.

Now regards the Kill power or Kill signal to VFD then I used to be Kill Signal guy but I'm now I Kill all power. Reason being what happens if the signal breaks or Even the VFD goes faulty.?

The signal should be wired such that if the wire's broken or otherwise interfered with the signal changes state and the system stops. The VFD going faulty sounds exceptionally unlikely, but if you're worried about that then just have a timed relay to switch the VFD power off a couple of seconds after the signal (as mentioned earlier), since by that point the spindle will have stopped so you wont damage the VFD by cutting the power, and if it's not stopped then the VFD has gone faulty so you probably don't care about risking damage to it by cutting the power.

E-stop is hit due to Limit or some other none spindle related condition then doesn't really matter how long spindle takes to slow down and coasting to a stop isn't long or problem.

My new spindle takes 107 seconds to stop from full speed if left to coast. I tend to agree that it's not really a problem though.

*emergency stop button pressed - strategy 1 or 2

Two, see above. You could take advantage of the enable signal on the stepper drivers to disable them, then link cutting the power to the delay associated with the VFD.

I also think the braking resistor is not required because of the fairly low inertia of the load.

Yes - the internal resistor is sufficient to stop the 2.2kW spindles in less than a second, so you can easily implement the above method.

(3000th post... )