Control Schematic Advice

[GTJim]

Nice drawings Jim, here's what I see;

1. Pin 6 of PMDX-107 should go to VFD ACN (ACM ?) (GRD) terminal.
2. Why is there a switch in the PILZ terminal A1 supply ? it's not normal.
3. Can the PILZ relay contacts handle the VFD supply current ?
4. Can the PILZ relay contacts handle the 70V PSU input current ?

Hi Eddy,
1. I have gone through manual and agree so I have amended the design.
2. Well Dean has responded to this, so I guess its a matter of personal choice.
3 & 4. Now this is getting a bit deep for me, but if I am reading the Pilz documentation correct the safety contacts can handle 240VAC and 8 amps, but I stand to be corrected.

Thanks for your help
Jim

[EddyCurrent]

Well that depends doesn't it.? . . . . It's normal for me.!!

I often put control panels on the front of the machines and having this cut power to relay is a bit of safety so the relay can't power up when changing tools etc. 24V is Safer than running high voltage into machine and messing around turning main cabinet supply off.

I'm not going there, do what you want, what I'll say is, it's not normal for the numerous industrial installations I've seen. 'Isolation and immobilisation' is a subject in itself.

Hi Eddy,
3 & 4. Now this is getting a bit deep for me, but if I am reading the Pilz documentation correct the safety contacts can handle 240VAC and 8 amps, but I stand to be corrected.
Thanks for your help
Jim

If the PILZ document says that and the VFD and PSU take less current then it sounds fine, the only issue I'd think about is the inductance of the 70v PSU transformer when the contacts open. This is why I used a separate contactor because it's cheaper to replace a worn out contactor than it is to replace the PILZ relay. Having said that I've just looked at your drawing and I can see the load is split over 4 separate contacts in the PILZ (2 in series then those in parallel with another 2 in series) so that might be okay provided they all open at the same time otherwise the first one to open gets to break the arc.

[GTJim]

I have included a soft start on the 70V power supply to control the inrush current so this should prevent any issues, shouldn't it?

[EddyCurrent]

I have included a soft start on the 70V power supply to control the inrush current so this should prevent any issues, shouldn't it?

It will for switching ON but I'm talking about switching OFF

Read on page 1 under "Inductive Load"

http://www.nkkswitches.com/pdf/electricalratings.pdf

It's not so bad that we are talking about AC where the voltage crosses zero at 50Hz so it helps extinguish the arc, unlike DC. I've had 'belts' off both and I can tell you it's easier to let go of AC than DC

[JAZZCNC]

I'm not going there, do what you want, what I'll say is, it's not normal for the numerous industrial installations I've seen. 'Isolation and immobilisation' is a subject in itself.

But that's just it Eddycurrent where not in industrial application we are DIY application and your just creating worries for people when they need not worrie.!!

I've had a second hand pilz relay on my machine for 3yrs now along with the On/Off switch inline with 24V switching 75v without any issues and before coming to me I'm pretty sure it had done plenty of work so I'm sure it will be fine Jim.

[GTJim]

Thanks for all the comments and suggestions.
I find this subject dificult as I'm more mechanical biased but have enjoyed the challange.
I'll make Si's amendment to the schematic and lets hope its somewhere near so I can look at the detail as thats bothering me.
More questions to come. Lol
Jim