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14th Sep 2020, 06:15 PM #1Most Valued Member
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VFD Input to flip between FWD/REV
Hi Everyone.
Im building a small control panel for my little home lathe. I have most of the VFD digital inputs set up okay but there is one thing frustrating me. I can get it to toggle between Forward run mode and reverse. i can command the spindle run in either direction but i would prefer a separate direction switch and a single run switch (so i can leave direction permanently set) this is a screw on spindle that can do up to 4000 rpm so id like to be able to lock out reverse.
Its a powtran PI500 vfd, ive scoured the manual. the pendant does have a way to do this i just cant find out how to do it with the digital inputs.
Any help appreciated!
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14th Sep 2020, 06:21 PM #2Member: Blue and white apron brigade
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There should be a VFD parameter that allows you to lockout reverse if you want.
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14th Sep 2020, 06:27 PM #3Most Valued Member
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I was hoping to do it with physical controls if possible but thanks for the thought its a good backup.
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14th Sep 2020, 06:38 PM #4Member: Blue and white apron brigade
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Let me get this right, you just want into run fwd - ie no reverse?
If so - why not just physically remove the reverse switch?
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14th Sep 2020, 06:48 PM #5Most Valued Member
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Sorry i should have been clearer.
I want to run in FWD 95% of the time. But reverse is handy for screwcutting.
I only want to have one Run pushbutton, the direction of which is determined by a two position switch.
Thanks again.
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14th Sep 2020, 06:50 PM #6Diamond Member
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Sounds like he want's a 2 position selector switch for FWD and REV and then a single push button switch for Start and I guess another for Stop?
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14th Sep 2020, 07:06 PM #7Member: Blue and white apron brigade
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OK I get it.
Did you look at 3 wire control options?
I know some people like push buttons but I like visual verification of what the machine is supposed to be doing so I use a single toggle switch for all 3.
Up = fwd, stop middle position, Down = rev.
One look at the switch tells me visually what is suppose to be going on - this comes in very handy - like I might have accidentally put the Hz down to zero
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14th Sep 2020, 07:10 PM #8Most Valued Member
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I would love to do that but im a touch limited by the buttons etc i have at hand. I only have some telemechanique buttons and panel i pulled off an xray machine and we are in full lockdown. I only have two position latching switches and momentary pushbuttons at hand. as well as no relays to do any latching.
Another way to solve my issue would be if i could get a momentary button to latch the start relay in the VFD but i cannot find a way to do that (the start button on the pendant does this)
The manual is extremely unclear about how the three wire method is used unfortunately.
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14th Sep 2020, 07:45 PM #9
Should not be hard to set up a relay to latch on from a NO momentary and release with a NC momentary. This is the basis of all NVR switches etc. You just need the two switches and a dpdt relay with a coil voltage equal to the DC control voltage output from the VSD.
Connect from the DC+ve output to the common on the Stop switch, then from the NC Stop switch terminal to one end of the relay coil. Connect the other end of the relay coil to the Common on the START switch, and the NO START switch to DC -ve. Connect one set of NO relay contacts in parallel with the start switch, and the other set between either the DC +ve or -ve terminal and the run terminal, depending on whether the VSD expects active high or active low inputs.
When you press the momentary START switch allows current to flow through the coil and engage the relay. As the relay engages, the relay contacts in parallel with the START switch will latch the relay when you release the START switch. At the same time, the second set of contacts will pull the VSD Run terminal either up if connected to DC + or down if connected to DC -, and maintain that state as long as the relay remains engaged. Pressing the STOP button removes the DC+ from the relay coil and releases the relay, opening the relay contacts that are controlling the VSD and latching the relay.
A separate switch controls the direction of rotation.
If the VSD requires separate Stop and start commands, this can be achieved by using a 3PDT relay with a contact set for latching, one for stop instruction, and one for start instruction.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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14th Sep 2020, 09:27 PM #10Most Valued Member
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Thanks everyone for your help. With a bit more reading I got a combination of a two position with neutral switch running forward reverse fine.
Thanks everyone for your advice. Only thing left is getting all the 24v lights wired up.
Sent from my SM-G973F using Tapatalk
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14th Sep 2020, 10:11 PM #11Most Valued Member
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Be careful you don’t set your deceleration time too short or your chuck may unscrew itself when you stop the machine. It’s happened to me and it’s no fun.
Chris
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