Spot the connection

[john fletcher 1Participant @johnfletcher1]

I have three inverters all of different make. I have wired each of them via a 20 amp relay to give No volt release. Each station has a large red e stop button together with a local stop, start, reverse and jog buttons. The control wires are screened ex computer cables and fortunately I don't have a interference problem. I have used Sy screened cable from the inverter to the motor and all three inverters are now mounted in ventilated steel boxes, trying to stop interference escaping. When I set things up I walked around the workshop with a radio seeking out any leakage. I wouldn't consider interrupting the inverter output in anyway the energy has to go somewhere and why should anyone need to disconnect the motor from the inverter output, am I missing some thing? . Anyway that is my experience with inverters and I'm pretty pleased with the inventers. John

[Mark CParticipant @markc]

John, SY is not really a "screened" cable. You need CY which is classed as a screened cable rather than the steel braid used in SY which is armour rather than screen.

Mark

[Neil WyattModerator @neilwyatt]

I've just realised this thread should probably be moved to the Astronomy topic…

Neil

[Mark CParticipant @markc]

Neil,

That would confuse matters and Steve is unlikely to get any help from me setting his inverter up as I would only look at a post under that heading if it is either very popular or of some intriguing subject.

However, I might be missing the point of the comment completely, or is it a Bill moment?

Mark

[Neil WyattModerator @neilwyatt]

Sorry Mark,.

Though many people seem to enjoy astronomy as an adjunct to model engineering, there are a few people who feel that if it is to be discussed it should be shrouded like a victorian table leg.

This morning I twigged that this thread was subtitled "Help needed to locate the star point", and I desperately wanted to get some levity back into the issue… hence the attempt at humour…

Neil

[Steve PaveyParticipant @stevepavey65865]

I think there is a difference between thread drift and legitimate thread development. In this case, I have (I very much hope!) sorted out the star point and have now re-installed the motor and in the middle of removing the old wiring and working out how to use as much of the existing control gear as I can. All related to the installation of the VFD (which has now been stuck 6 miles away at a parcel depot in Gatwick for the last 36 hours thanks to Yodel).

Anyway, it looks as though the re-wiring is going to be considerably simpler than it was – particularly enabling the fwd/rev switch – compared to the previous 3phase setup. I'm slowly starting to understand what Mark meant by 2-wire control I think!

The advice has been invaluable so far, thanks to everyone, but I'm sure there are more questions to come.

[Mark CParticipant @markc]

Neil,

As a sad social outcast (mechanical engineer) the link was slightly to obtuse for me without you pointing it out, but now I see your point (he types with a smile)

Steve,

Yes, wiring an inverter is much easier – nothing like the amount of wiring or requirements of a 3 phase installation and much easier to add controls etc at a later date. It mostly needs almost no current (apart from the supply to and from the inverter) so you can almost make money cashing the scrap copper in (you might need to do more than one mind).

Mark

[john fletcher 1Participant @johnfletcher1]

To Mark ,I got it wrong it is CY cable which I used, its a long time ago since I did the wiring and got mixed up. Its all very good reading here and it is also good that people are prepared to share their knowledge and experiences. John

[Mark CParticipant @markc]

John, I agree, you might not always get the "book" solution but often people will talk from their own experience which is often far more valuable than the theory.

As a point of interest (and I thought I typed this already but can't find it, perhaps a senior moment), did you ground both ends of the screen on the output cable? Normal practice is to ground just one end but that is to keep interference out, you want to keep it in so both ends need doing.

Mark

[Steve PaveyParticipant @stevepavey65865]

Partial success, thanks to all the help. I've removed all the original wiring from the lathe as it is all redundant, but I will be keeping the switchgear and using it to control the vfd in due course. I decided to get a new dol starter as the original had the wrong coil and overload for the 240v supply. I already had a convenient 16A outlet wired as a radial circuit with a 16A mcb.

I really struggled with the manual – it omits basic information, has no logical order to it and assumes that you've set up dozens of the things already, but I found a few useful forum threads on a cnc website explaining which parameters are important and what the settings are for this type of induction motor. Happily, my star to delta conversion seems to be ok and the motor spins happily at 2900 rpm. More wiring to do after I install the motor, and then I'll sort out the control switching.

[Mark CParticipant @markc]

Steve, sorry it took so long but here are the settings I used:

1. PD 001 = 1
2. PD 002 = 2
3. PD003 = 50Hz
4. PD004 = 50Hz (MOTOR FREQUENCY FROM MOTOR PLATE)
5. PD005 = 50Hz
6. PD014 = 4 SECONDS (START ACCELERATION TIME TO SET SPEED)
7. PD015 = DECELERATION TIME IN SECONDS (not required if coast to stop set)
8. PD023 = 1 (ENABLE REVERSE ROTATION)
9. PD026 = 1 (COAST TO STOP, UNCONTROLED DECELERATION)
10. PD044 = 2 (RUN FORWARD)
11. PD045 = 5 (CHANGE DIRECTION FORWARD/REVERSE)
12. PD046 = 4 (STOP)
13. PD141 = VOLTAGE FROM MOTOR PLATE IN DELTA (PROBABLY 240/250 VOLTS)
14. PD142 = AMPS FROM MOTOR PLATE IN DELTA (THE BIGGER VALUE)
15. PD143 = MOTOR POLES ( IF IN DOUBT, SEE BELOW)
16. PD144 = MOTOR RATED SPEED RPM FROM MOTOR PLATE

Motor pole count = 6000/(motor rpm x 1.0526)

EG. For 50Hz motors, 2850 rpm = 2 pole, 1425 rpm = 4 pole, 950rpm = 6 pole & 700rpm = 8 pole

This is the switch wiring I have and remember that the speed pot needs its own ground separate from the digital input ground (in other words you need 7 wires). The settings I used give a 10 volt signal on the speed pot (10k ohm) but you can change it to 5 volt or current sensing with PD070 and you can set/change a filtering function on the analogue input with PD071 (factory setting is 20).

How does it compare with your settings?

Mark

[Steve PaveyParticipant @stevepavey65865]

That's really useful Mark, thanks. I think most of the settings are the same, but I need to check PDO 26 as I have set 14 and 15 to 10 seconds. One thing that I didn't check on my first test was 143 and 144 – I have now changed them to suit my 2880 motor but they were set for a 1440 4 pole. Strangely it made no difference (checked with a hand held tacho) but at least it is now correct for the motor.

PD142 is set at 11A – as it was originally a star motor it doesn't have the delta info on the plate of course, and I have no real idea what the current should be now except that it will be higher than the 5.8A shown.

Neil mentioned that the control inputs are configurable for either latching or non-latching switches (I guess he may have been thinking of his own IMO inverter) and I can find no reference to this in the manual or with a Google search. I already have a 3 position 4 pole rotary switch on the lathe, but my tests with a multi meter indicate that it is not making very good contact on any of the 4 poles so I may have to buy another one. If someone can confirm that I can use a latching switch, and if there are settings relating to this on the inverter I would be very grateful. I would also like to get a nice big chunky 10k linear pot (or one that will accept a big chunky operating knob in true Harrison style) so again, any recommendations will be welcome.

[Mark CParticipant @markc]

Steve,

You can set the digital inputs in a number of modes but to answer your specific question, if you have the inputs wired and configured like mine you can't use a latching start switch otherwise the machine will start up when you turn off the stop button (or release it if it is momentary). The direction switch can be latching (mine are).

If you are using a rotary switch you can wire it such that turning it one direction provides both the stop signal (which is inverted – no signal = motor off) and the run signal with a separate contact for forward and reverse (no signal = forward). Turning it the other direction gives the run and stop signals and also a signal on the reverse input to make it rotate in reverse.

I have my Boxford VSL wired like this on the original rotary switch but I have a spring return "start" position in forward and reverse directions and have the start input wired to the momentary positions. In other words, my rotary switch has a central "off" position and two forward positions (direction forward and start) along with two reverse positions (direction reverse and start) so a five position switch with the two "end" positions being spring return "momentary" positions.

Mark

[John RuddParticipant @johnrudd16576]

Fwiw,

I have my HY inverter wired like this:

Three position switch wired so that it is FWD-OFF-REV, then my speed pot has a switch wired such that when turned anti clockwise to the off position the m/c stops….

I could if I chose to, with direction sw set FWD, then set speed, the use the direction sw to stop start….

I prefer to set the direction, then stop/start ramp up/ down as needed…,

[Mark CParticipant @markc]

Just to complicate matters further, if you want to you might set up a forward, off, reverse switch as John above and then set the pot to have a mid point bias so that in the middle of its range you get 0 revs (stop) and twiddling the pot forward or reverse gives motor speed proportional to forward or reverse rotation position…. you might want a positive detent for the pot so you can easily find the off point!

Mark

[Mark CParticipant @markc]

Steve,

I noticed you did not know what the amperage was as you converted from star to delta. You can work it out by dividing the original voltage (380V) by the single phase voltage (240V) and multiplying the original amperage by the result.

so: (380/240) x 5.8A = 9.18 amps in your case.

Mark

[Steve PaveyParticipant @stevepavey65865]

 

Up and running successfully at last. I've tidied up the wiring into the inverter, adding the screened cables for the controls and routing all the cables properly. I removed all the old wiring from the control panel on the lathe cabinet, along with the old duff fwd/rev switch and welded up all the mounting holes, drilling new ones for the new switches and buttons. Final touch was to make a control knob for the 10k potentiometer in the style of the existing (give or take – I had to use what bits and pieces I had lying around). I've now had the lathe running for an hour or two, with everything working as it should and better than I expected, given my complete ignorance about VFD's before this little project.

Edit – I still have to find a tiny brush and a splash of red paint to touch in the symbols on the panel, which will probably take a few months to get round to!

Edited By Steve Pavey on 19/10/2015 21:21:18

[Mark CParticipant @markc]

Steve,

Can I take a guess that your new red button is possibly an e stop? If it is, you really want to change it for the type that sticks out rather than a "shrouded" type so if you have to press it you can strike it effectively without taking to much of an aim with a digit!

Mark

[Steve PaveyParticipant @stevepavey65865]

I was rather hoping that no-one would notice that – unfortunately I was seduced by the quality of these switches (from RS) and they don't do a mushroom version. If I can find a bit of red plastic rod of some sort I will turn up an appropriately shaped button and superglue it to the top of the existing.

[Mark CParticipant @markc]

Steve,

If you pop into your local CEF (city electrical factors) they should have one like that with the correct business end – probably a less than a tenner especially if it is a standard fit back.

I always hate getting switches from RS, no matter how hard I try to get all the bits I always seem to be missing something important or order too many bits etc. Why they cant simply list all the bits needed for a simple switch configuration (a switch configurator, like the systems pneumatic companies use) is beyond me. The cynic in me thinks it is so they can make more money from me having to order lots more stuff than I originally thought – goes along the lines of;

"ok this is the right price, I will get some of these switches" – parcel arrives, "oh bugger, there are no locking rings/contacts or whatever else is needed in the box….."

Mark

[mick vannParticipant @mickvann94362]

Hi Steve,

Would you mind letting me know the sequence of your switch gear ( it looks an excellent setup ), is it isolator, DOL then VFD, or can you put the DOL between the VFD and Motor ? Any help you can give would be greately apreciated,

Mick

[Neil WyattModerator @neilwyatt]

As a general rule you shouldn't have any switching between inverter and motor.

Neil

[KWILParticipant @kwil]

Mick, the connections from a VFD must be direct to motor without any switching, you may put the DOL before the VFD.

[mick vannParticipant @mickvann94362]

Hi Chaps, thanks for the replies, can I ask why you would need a DOL before the VFD, what would this achieve ?

Sorry for been thick, I am but a lowly Plumber.

regards Mick

[Steve PaveyParticipant @stevepavey65865]

Sorry for nor replying sooner – yes, the supply is from a 16a commando socket to the DOL starter, then to the inverter. You don't actually need a starter, but because commando sockets are unswitched, and commando plugs are unfused I decided that the simplest method of isolating everything was using a dol starter. I could have used an industrial isolater, but they are just as expensive.

Since the last photo I have restored the LoVo light and fitted it with a 12v led lamp. This operates from a seperate 13 amp socket outlet, which also provides the supply to the coolant pump (or it will do when I get round to sorting the coolant pump out).

I have just bought a little Boxford shaper, also 3 phase, so I'm just about to repeat the process (when I find a suitable vfd in the classifieds). Hopefully I won't have to ask questions this time, but I will try to take some photos and post some details in case anyone is interested.

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