K3 controls power to the servo drives, the N/C contact on the XPS monitors the K3 unit, if it is jammed or fails to open, the XPS does not pull in and Mach will stay in reset as well as no spindle relay/contactor supply.
If K3 jams on despite pressing the E-stop or limits, it will not latch-in again.
It was a reasonable safety enhancement i think.
As with all systems, a catastrophic failure - in this case K3 welding shut on one or more lines will still leave a danger but the chances of a contact weld at these low currents is pretty rare i think?
You do realise that a standard contactor is designed so that if one contact welds shut, the others will still open?Avoiding the rubbish customer service from AluminiumWarehouse since July '13.
Interesting, would the carrier still lift the aux contact block though? On these Sirius range of contactors, the monitoring/feedback contacts are by way of an aux contact block mounted on top.
The XPS will not work without an N/C pair on one of the output channels.
I never realised the XPS was through a NC contact.
It'll depend on the spec. Some will be designed so the contact closes regardless, others will hold it open. On larger contactors, you can normally wedge a small screwdriver in and close a single contact, which would then let you see if the NC contact opens or not, however smaller contactors are usually far more enclosed.
Having said that, at the currents you're working with, the contactor should never weld shut, so I wouldn't worry about it. Even if it was to stick and maintain full power, the power being maintained should not be the sole reason if the machine wasn't to stop during an e-stop.Avoiding the rubbish customer service from AluminiumWarehouse since July '13.
I just like having things covered as far as practically possible - in this case if the e-stop is pressed, the CSMIO is told to stop as well as power being removed from all servo's and VFD's, both via separate channels. I think that should be ok, the XPS contacts are forced apart so pretty much guaranteed to open.
BTW, what happens if a servo encoder fails - does the motor runaway or stop??
On an AC/Brushless motor, the drive should detect a fault.
With a brushed DC motor, potentially run it into the limits at great speed.Avoiding the rubbish customer service from AluminiumWarehouse since July '13.
The Following User Says Thank You to m_c For This Useful Post:
Got the panel finished, bench-tested, all passed 100% :)
Got the pendant rough-wired so i could bench-test the panel, seems functional.
All axes homed and jogged perfectly, no surprises, e-stop system seems to work ok.
Managed to lug the panel into the cabinet, nearly ruptured myself but it's in now and bolted down.
Tomorrow will be final wiring on the switches and limits etc, plus re-rigging the pendant for the next power-up test. Then I'll probably strip the pendant and send it out for powder-coating, or just spray it if impatience takes over ;)
Nice job Dave..Clive
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