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Following from Jonathan's post #99

Transformer Inrush - Open Electrical

I'll back up this based off experience because I often use 500 & 600Va transformers without any trouble with inrush trips. If there ever is I just use C or D rated MCB and I'm sorted.

That is true for a pure resistance, however the issue is the transformer in this case is better modeled as an inductor. I followed Eddy's links but unfortunately they only give 'hand waving'...

There is a lot to be said for the KISS approach.
No point complicating things anymore than what you really have to!

Not when starting something like a transformer. A mains powered transformer essentially has a zero current point 100 times a second, so if you can switch on at exactly that point, you won't see any...

You would be fine with 625VA and no soft start circuit, so if you restart the PSU with the thermistor still hot the current is still going to be less than without anything, so either way it's not a...

Alternatively, use a zero crossing point SSR to power on the transformer, which greatly reduces any switch on surge from the transformer itself. And if you really find a series resistor necessary,...

If the rating of your transformer is less than around 600VA, I wouldn't bother with any soft start circuit.
Thermistor is an easy option, as it's resistance decreases with temperature so no real...

An easy way to provide the limit override (non-locking) and start (locking) logic is with a diode:


6929

An alternative would be to use a seperate contact on Relay 2 to enable Relay 1, but I...

So, you have a 50v AC transformer giving 12A, what about the rest of the components?

Here are my suggestions and the calculations needed to ensure it all works reliably...

Bridge rectifier: Buy...

Ok the calcs you've done are close and correct in some ways but some of what you read I think you miss understood.? The 752s Manuel and 50-70% was referring to current not voltage. So you still need...

Looks like you're after an explanation of why, not what...

I would consider the voltage you get from the common formulas (20*V, 32*L^0.5 etc) to be a 'recommended minimum'. You will get better...

Iv added another diy brushless spindle to my growing collection and thought id post my adventures just in case anyone was in the market for a quiet spindle with low rev torque for cutting plastics...

Depends on a few factors really and the drives being used also play a big part to how micro stepping is implimented.

10x micro stepping is about the max usable and beyond this is just pointless...

You could mill a pocket in the shaft side of the aluminium to accommodate the pulley if there is not enough space.

Pulleys are definitely good plan as they will let you change the ratio allowing...

IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

Jim

The bearings should be like in 1. i.e pressing against the plates. Fix the bearing(s) to the end of the screw by having a thread and a nut on the screw to lock it in place.

Those bearings you...