Harrison M300 VFD wiring to include apron control lever

[AJAXParticipant @ajax]

I plan to convert my Harrison M300 to run from a single to 3-phase VFD drive.

WEG CFW300 IP20 2.2kW 230V 1ph to 3ph AC Inverter Drive, DBr, Unfiltered
CFW300B10P0B2DB20 (13059419)

I have used WEG inverters in several other machines and found the wiring to be very straightforward (start, stop, e-stop, direction and speed control) but the M300 presents a particular challenge and I am interested to know how others have used the apron spindle control lever.

The spindle lever mechanically latches in one of three positions to select forward / stop / reverse. The lever rotates a cam that acts on two micro-switches. Effectively, this whole system acts as a latching switch and not the more appropriate momentary action switch used with most VFD setups. Consider what would happen if the spindle was running and an e-stop was pressed and then cleared. The spindle would start automatically.

I have considered using a PLC or timer relay(s) to convert the switch logic levels to timed pulses, thus simulating the effect of a start / stop push button. However, I wonder if there is a simpler solution that I am ignoring?

[AJAXParticipant @ajax]

[John HaineParticipant @johnhaine32865]

Capacitor, resistor and diode for each switch.

[Simon Williams 3Participant @simonwilliams3]

E Stop function requires a second (confirming) action to achieve reset, so the machine can't restart as soon as the latching estop button is released. So you need a dedicated estop relay which drops out when the estop is pressed.

Now imagine you can only re-energise that relay if the spindle control lever is in the central "off" position. Hopefully the micro switches it operates include normally closed contacts which can be wired in series into the reset path of the estop relay. I think you'll find this function is built into the original control circuitry as manufactured.

BTW I don't believe the estop relay needs to be a safety relay, a simple control relay will suffice.

HTH Simon

[DC31kParticipant @dc31k]

Posted by AJAX on 30/10/2022 08:29:18:

Consider what would happen if the spindle was running and an e-stop was pressed and then cleared. The spindle would start automatically.

No. Or at least, not unless you configure it specifically to do so (there are, for example, processes that you might want to resume autimatically after a power outage).

The answer to your question lies not in anything on the lathe but in the configuration of the VFD. Read the manual from cover to cover and understand what each parameter and each input path does.

The VFD can be made to work with both momentary inputs, maintained inputs and possibly a combination of the two.

There is no VFD sold that will, by default, spring back into life when the E-stop circuit is activated and then released. At best, it will revert to a 'ready' condition awaiting a positive 'go' signal via another path.

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