Key switch to enable lathe operation Ensure 440 volt supply before load applied - see Transwave converter info. Provide 2 off 13 amp sockets for tool post spindle etc that are controlled by the lathe enable & emergency stop switches Overload protection for the lathe.


David Smith 2/11/16

Also, we might be able to get it cheaper than that. www.electriccable.co.uk charge only £1.19/m + VAT, but then charge £9.50 + VAT for delivery. So, perhaps we can find somewhere that does it for a reasonable price but with cheap delivery. Searching around, CEF sell it by the cut length, and they have a place in Avonmouth, but they don't list a price on their website. It might also be worth asking Edmundson Electrical just up the road from the Hackspace, next to Screwfix. They certainly sell it; it's whether they do it in cut lengths or just whole reels.

We still need to figure out the configuration and exactly which thermal overload to buy.

I've been researching into this; this is what I've learned:

o Yes, the current value quoted for the thermal overload really is the expected current consumed by the motor. Even the 100 mA ones (although I don't know why you would bother having a 100 mA, three-phase motor…) o For the overload to be truly effective, I think it needs to be one per motor. I have a sneaking suspicion that there is more than one motor in the lathe, although ICBW. o Therefore, we need to confirm both (a) the number of motors in the lathe, and (b) the maximum full load current (also called FLA (full load amperes)) of each motor. o If there's more than one motor, we should consider either mounting the box on the lathe rather than the wall, or the thermal overload relays and associated contactor in the electrics box on the end of the lathe rather than in the new control box - otherwise, we'd end up with multiple three-phase cables running from the box on the wall to the lathe, which seems rather excessive. o The thermal overload relay doesn't actually switch off the current to the motor. When overloaded, it opens the NC contact, which should then turn off the contactor. Therefore, we need to wire this contact in as another “emergency stop” button. o In addition, when tripped, the thermal overload relay also closes the NO contact. If we wanted, we could wire this in to, say, a neon indicator on the box to show that the overload had tripped. o Do we want a manual or automatic reset? The Chint ones are all manual override, but other manufacturers also do automatic ones that reset themselves after a minute or so. If we had a manual trip, it would mean that, whenever it was triggered, it would render the lathe unusable until someone authorised to open the control box could get down to the Hackspace and reset it. Is that what we want?

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