Machine safety relay or not?

[netblindpaul]

gerard,
He is wrong, there are others.

 

[Darkwood]

This subject of e-stopping a drive has got many a forum scratching their heads, firstly you need to evaluate what exactly you require the motor to do in an e-stop without the obvious STOP IT! been suggested, is it safer to shut power off and let it coast or will a controlled decel' DC injection be more practical for example.
As ive mentioned before dropping power off upstream of a VSD should be considered a no-no as a no' of issues can occur from a longer coast to stop time as the drive dumps stored energy into the motor to drive corruption, also if fitting a contactor to the output side some drives can be left in a ramp up state so simply re-engaging the contactor could give instant motor run as the drive has only gone into a motor blind state. You should then try to employ the practice of both having an 'Enable/run' function open circuit as well as a contactor between drive and motor. A chat with the drive manufacturers may be required as using Enabled/run function will in most cases allow a safe E-Stop function but few drive have been designed around this and thus dont comply with current standards when using this setup for E-stop as issues of fail-safe etc have to be considered, ABB are one brand that do comply in some of their models as mentioned before and im sure others are out there too, all in all their has to be alot of thought put into the control system, a risk assessment of how the Motor is required to stop whether its safer this way or that etc etc .....

 

[gerard]

gerard,
He is wrong, there are others.

Ok - well that must be the only type he knows of. At the moment i have an Emerson installed but if I am carrying out a similar application in the future, I will look for Inverter with the enable safety feature.

 

[gerard]

I am using the enable and run signal to stop the drive at the moment so that's pretty safe. As I said, I am waiting on a safety relay and sensor. I believe I am going above the original standard of safety set by manufacturer. The reason for my concern is due to the fact that I altered the machine and I want to be satisfied that I am doing my utmost to make it as safe as possible.