Ready Steady Eddy

[cncJim]

Also, and this is very important but open to interpretation, I am not removing power from the spindle inverter during emergency stop, I mentioned this is another post. The reason is that the inverter can stop the spindle faster than it will stop on it's own, it does this by applying dynamic braking. Other options for bringing the spindle to a timely halt would be a spring loaded mechanical brake or as in the case of my table saw, a DC injection braking system. 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. According to the machinery Regs. which won't apply in a private houshold situation, the spindle should stop within 10 seconds, now I've not had my spindle up to speed yet so time will tell how long it takes to stop on it's own.

Good info, thanks.
If I had your VFD rather than my cheap Chinese one, I might be more inclined to trust it to stop the spindle during an Estop as well.

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.

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?

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 (also how do you test an estop circuit if testing it may damage the equipment?!?).

I'm not that keen on the mechanical breaking solution, so that leaves the following:-

EStop

• Dynamic/Rheostatic braking
  Cut cables from inverter to spindle and attach spindle to a bank of breaking resisters to apply dynamic breaking (is this even how it works!?!). At same time cut the run cable to the inverter.
• DC injection braking system
  Same as above but DC injection brake cuts the link from inverter to spindle and applies DC to the spindle to stop it.

I like the idea of the DC injection braking system but they seem pretty expensive (RS DC Injection Brake @ ~£160 with VAT!). I wonder how easy/cheap it would be to do dynamic braking (without the vfd)?

edit - 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?