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Startrite 275 3phase to single phase vfd conversion...again

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Lightning bolt

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I have posted on this topic before & gained fantastic knowledge & insight on the subject. Thanks to everyone who replied & all the great posts on this forum concerning this popular subject.
Kinsella's account of his journey was a great help.
I'm 90% there with it & on the final hurdle. Sorry I haven't got myself sorted to post pics yet.

Here's what I have so far:
-Brooks crompton 2.2kw motor re-wired to delta configuration.
-I have the motor out of the saw & wired to an 'Rs 510' vfd from drives direct. Which is wired up to the mains via a 16amp plug.
-We got them running nicely together after some severe head scratching re the parameters (which turned out to be relatively straightforward once I patiently read the manual properly...).

-The final hurdle: a sparky mate has told me the existing 'allen brown' switch gear has a 3phase coil & won't work with my set up unless I change the coil to single phase.
I'm very unconfident with electrics so don't fancy this option. I basically want to find the easiest/safest option for turning on & off the saw. & don't mind paying a few quid for a new single phase switch as it'll be used for my full time job. Was looking @ nvr switchs on axminster...would something like that work? Also there's a red mushroom kickstop button mounted on the machine. Could this be wired into an nvr switch? Any pointers much appreciated.
Ps: my vfd has 3wire control via terminals +24v (com), s1 & s2 (start & stop)...
 

Doug B

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Just wire a switch out of the VFD alternatively I used to have an old 3phase Wadkin planer running through a VFD I turned that on & off with the push button on the VFD itself.
 

Lightning bolt

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Just wire a switch out of the VFD alternatively I used to have an old 3phase Wadkin planer running through a VFD I turned that on & off with the push button on the VFD itself.
Hi Doug,
Thanks for the reply. That was actually my question. What kind of switch should I get to wire into vfd?
I'm self confessed clueless when it comes to this stuff...
 

Doug B

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Not being an electrician I would go back to drives direct & ask them what they recommend, looking at their site they appear to have stop/start switches.
 

Sandyn

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I just use my VFD for controlling my meddings drill. I removed the switch from the drill and use the VFD start/stop buttons, but eventually will take the controls to an external set of switches.

Don't put any switching in the 3 phase from the VFD to the motor. It may(will sooner or later) cause damage to the VFD. Hard wire with good connections
There is a run and stop button, on your unit that will start and stop the saw or it looks like you can use a momentary push button switch to connect S1 to 24V to start and S2 to 24V to stop.
You will be able to get suitable switches on Amazon: something like this (very quick look, there may be better/coloured).
https://www.amazon.co.uk/Momentary-...+momentary+push+button&qid=1606065298&sr=8-15
which has a 2A 36V contact.

If you wanted the push buttons to illuminate, to show if the saw is on or off, it would require different switch With 24V LED and a small bistable circuit which you can also get on Amazon. Hardly worth the effort. You know when it's running or not. The momentary contact requirement makes this awkward.
As Doug B says, probably worth going back to the supplier to see what they have.
Note you can probably program the stop time of the saw, I have that on my meddings so no matter what speed it is running at it will stop within 3 seconds. Have the VFD frequency set to 50Hz for normal running speed.
 

Ttrees

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Hello
Advice on switches may depend on what kind of system you want to go with.
I chose to have a hands free paddle for the saw for safety, this means two simple momentary buttons are required.
SAM_2105.jpg


Having a stop and a separate start button is whats called "three wire control"
These give a signal and have no mechanical parts, (when taken apart to the bare bones of it)

If instead, you used a single toggle switch you would have "two wire control"
A toggle switch is a permanent signal as a lever gets thrown into a position
(like a light switch)
Its more difficult to design a paddle for this.
Likewise a momentary button with a latch can have a similar permanent function, in that the button is pressed and held until you hit it again.

If you choose three wire control for use with a paddle
You could buy a push button station but expensive at about 15 quid
or make your own box to save on the cost.
Push buttons are really cheap.
I would chose a NO green button (you can go all fancy and get a LED one if you like)
and you need a NC stop, red is a good colour.
Many NC buttons have a latch or twistlock, which won't work with a paddle.

Here is what I found with a quick search, I have pictures of my 275 somewhere but cannot find all the treads to give you a clearer picture.
There are plenty of startrite 275 or tilt arbor threads concerning VFD/inverters.

Type this into the ebay search bar
1Pcs Push Button Switch xb2-ba31



The start pushbutton will need to be NO (normally open circuit)
and the stop button will need to be NC (normally closed circuit)
 
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Sandyn

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Interesting @Sandyn
I presumed the illuminated buttons would not need additional power to light.
Tom
I'm not sure if I have the correct data sheet for that particular VFD, so it depends on the output current capability of the 24V The data sheet I have says 30mA and the input current for S1 and S2 are 4.5mA, but momentary, so it would be feasible to drive the LEDs from the 24V. Only one would be on at a time.
 

Fitzroy

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Mr Bolt. Taking it back to basics so sorry if preaching to the choir!

Your VFD supplies direct to the motor, you can’t change that.

Your VFD will have options for control circuits. These can include start, stop, run, frequency etc.

These functions can either be controlled via the panel on the front or from add on switches and knobs in a location away from the unit.

The simplest to picture is a run circuit. The VFD will look for a closed circuit between two connections on its control bar. If you put a wire between these two connections the motor will run. You can then put any number of mushrooms, NVRs, and start switches as you want. See picture below.
D30B0861-D102-4FBC-A0B3-DF91A59186E7.jpeg


Assume B and C are emergency stop mushrooms. You first have to reset these to close them, then when you push the start switch A the circuit closes and the VFD will run the motor. If any of these open the VFD stops the motor. This control circuit carries a nominal voltage.

Using an NVR in the control circuit you have to power it from the supply before the VFD. The 240v supply just holds the NVR closed as long as there is voltage.

From a inherent safety viewpoint this is why a VFD is worse than a direct supply. Hitting a mushroom or kill switch does not break the supply to the motor it just tells the VFD to turn the motor off.


Fitz.
 

Ttrees

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It's worth noting that emergency stop might complicate matters also.
If you chose to stop the Startrite 275 very quick, beware that on my more recent machine anyways, there is a possibility of the blade becoming loose due to the thread on the arbor having right hand thread, so no use getting additional breaking resistor.

I have mine set to something like 7 seconds, (may have to double check this!)
 

Lightning bolt

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Much thanks for all the interesting & usefull info in your replies people.
Mr Bolt. Taking it back to basics so sorry if preaching to the choir!

Your VFD supplies direct to the motor, you can’t change that.

Your VFD will have options for control circuits. These can include start, stop, run, frequency etc.

These functions can either be controlled via the panel on the front or from add on switches and knobs in a location away from the unit.

The simplest to picture is a run circuit. The VFD will look for a closed circuit between two connections on its control bar. If you put a wire between these two connections the motor will run. You can then put any number of mushrooms, NVRs, and start switches as you want. See picture below.
View attachment 96943

Assume B and C are emergency stop mushrooms. You first have to reset these to close them, then when you push the start switch A the circuit closes and the VFD will run the motor. If any of these open the VFD stops the motor. This control circuit carries a nominal voltage.

Using an NVR in the control circuit you have to power it from the supply before the VFD. The 240v supply just holds the NVR closed as long as there is voltage.

From a inherent safety viewpoint this is why a VFD is worse than a direct supply. Hitting a mushroom or kill switch does not break the supply to the motor it just tells the VFD to turn the motor off.


Fitz.
Thanks fitz for taking it back to basics, that drawing has given me a clearer image in my mind of how the switching works.
I think i'll take the advice of contacting drives direct, it seems I can't go wrong there...sooo many options on ebay/amazon etc...could easily get the wrong switch...Ttrees I shall also take your advice & have the saw stop @ about 10secs. This is plenty as i'll be the only person using it 95% of time. My buddies wadkin saw used to take about 4mins to slow down for yrs! Dodgy...
 

Ttrees

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Nothings gonna blow up if you tried using unsuitable switches.
The wires are low voltage and won't shock you.
Many folks check the functions of the VFD are working before installation, and just join wire to wire without using buttons to check.
Once the circuit is broken the machine will stop, regardless of what basic system you would use, be it two or three wire control.

The important thing is not to have those switch wires touch the power input and output terminals,
And make note that these things need time to drain off after unplugging, as the capacitors hold a lethal charge!.
50/50 are the chances of your motor running in the correct rotation when you hook it up..
To fix this switch any two of the three wires from the motor over,
but wait for the caps to drain off for a good while first.

The next important thing is the parameters for speed,
make sure you enter the correct motor commands that relate to speed...
Selecting 50hz for a start, some cheap VFD's are setup default at 8 times this for use with CNC routers.

Making sure you know if its a two pole motor (running around 2840/3000 RPM)
or a four pole motor which runs about half that,
and keying in the correct RPM might be required on some drives,

Bob Minchin (Myfordman) has done this paper up regarding VFD's and his writings are about the best information you will find.;)

Induction motor information here https://drive.google.com/file/d/0B_GZrXNsNxTlQzd6aldlQjJtUDQ/view?usp=sharing

Tom
 

Lightning bolt

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Thanks for the info tom. Things gone hectic here, have to sideline saw for a bit. Will post success story when I have one!
 

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