VFD Safety

[kenmwallace]

In my Chevalier 1840 lathe retrofit, I have the Acorn controlling the Sureservo2 motors and now I am connecting the STEPPERONLINE 7.5KW 10HP 31A 220V VFD. Probably made in the same factory as the DuraPulse.

In other machines I build (non CNC) if my VFD does not have a Safe Torque Off (STO) input, then I am required to put two safety rated contactors in series between the motor and the VFD. This is controlled by the safety system (light curtain etc). This is for safety standards compliance.

On my lathe project, I could put a switch on the sliding cover that would control the contactor that delivers power to the VFD, but then every time I close the cover I would have the delay while the VFD boots up.... around 6 seconds.

I have been reading the forum archives and I see that some have put a relay on the VFD's control common so the run command can be disabled. This seems like a good idea.

Any other thoughts on this?

Ken Wallace
San Diego

[cnckeith]

Ken,
VFD incoming AC power is commonly run through the Estop contactor of a CNC control system that way a 'fault' from any number of sources will shut off the spindle power. If you are looking to configure an inhibit that is different and can be done a number of ways. Acorn has 'stock' door safety logic available and built into the Wizard or you could bake your own with by modifying the PLC program logic

[Muzzer]

I'm not familiar with Stepperonline products but they seem to offer 2 VFDs (H100, B600). The H100 seems to be less expensive and comes with STO. Would that be a simpler solution?
https://www.omc-stepperonline.com/downl ... Manual.pdf
https://www.omc-stepperonline.com/h100- ... 0t20075bx0

Interrupting the AC input won't provide a quick, safe STO behaviour and it's not a great idea to disconnect the motor from the VFD when running under load.

[kenmwallace]

The Stepperonline VFD seems to be an incredible deal. I bought the H100, but the STO feature requires an upgraded controller board. I have not figured out how to order that yet. I don't want to kill the input power due to the boot up time. My implementations with other machines using motors in the 10 hp range with safety contactors between the VFD and motor have worked fine. Probably some back-EMF suppression on the motor side would be a good idea, but I did not do it.