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awemawson:
There are 'soft starters' available for three phase motors that would cure your problem. Most nowadays are electronic varying the phase angle that a triac is triggered at, but a simple one can be made with a time delay relay and three high power resistors. The resistors go in series with the three phases of the motor feed (or one phase of a single phase motor) and the relay contacts short the resistor out a pre-determined time after start up.
rotorhead:
Hi awemawson,
Not being altogether very electronically savvy, but managed to wire up the remote for it to work as intentioned, as the vender whom sold it to me, did include a very simplified wiring diagram, I don't have the requisite skill to go down the route you have kindly suggested.
I'm not really sure soft starting is the problem, as this VFD does start up slowly even with the variable switch set at full Hz, on the lathe it's the sudden inertial loading of spinning up the heavy chuck mass, that can cause the trip out, then it's just a case of switching off the power, to, I presume let it reset itself and then restart it.
On the miller, with such a large and heavy gear train (It's a big machine, the original motor was 10Hp if I remember rightly, I'm now driving it with a 3Hp albeit with twice the revs, to theoretically get the torque requirement, and driving it on the lowest input speed pulley), if I don't take care to set the Hz to zero, it also sometimes trips out from a cold start.
philf:
--- Quote from: rotorhead on November 14, 2012, 04:41:40 PM ---Hi awemawson,
Not being altogether very electronically savvy, but managed to wire up the remote for it to work as intentioned, as the vender whom sold it to me, did include a very simplified wiring diagram, I don't have the requisite skill to go down the route you have kindly suggested.
I'm not really sure soft starting is the problem, as this VFD does start up slowly even with the variable switch set at full Hz, on the lathe it's the sudden inertial loading of spinning up the heavy chuck mass, that can cause the trip out, then it's just a case of switching off the power, to, I presume let it reset itself and then restart it.
On the miller, with such a large and heavy gear train (It's a big machine, the original motor was 10Hp if I remember rightly, I'm now driving it with a 3Hp albeit with twice the revs, to theoretically get the torque requirement, and driving it on the lowest input speed pulley), if I don't take care to set the Hz to zero, it also sometimes trips out from a cold start.
--- End quote ---
From this and your previous post I'd say that you should avoid using the clutch altogether to start the lathe - use the controls on the VFD (or remote controls) to start and stop it - it's the only way that the 'soft-start' on the VFD will do any good. It should be easy to adjust the acceleration/decelleration times to avoid tripping the VFD providing it's of adequate capacity.
rotorhead:
Hi Philf,
Thanks for that, I have to admit I hadn't even given that any consideration, a very good pointer, the VFD is a 4Hp one, powering 3Hp motors(not at the same time).
I'll try it out now I've completed another mod to my VFD/socket arrangement.
I was fed up changing over plugs from the lathe to the miller, so now I've installed a changeover switch, to have both motors plugged in, but just turn the switch.
awemawson:
You can kill the output devices on a VFD by switching it's output. I'm sure you only swap plugs when everything is off, but your arrangement would allow 'hot swapping' which would likely result in the VFD dying.
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