2 pole or 4 pole for Myford ML7R

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2 pole or 4 pole for Myford ML7R

This topic has 83 replies, 14 voices, and was last updated 20 September 2023 at 21:36 by noel shelley.

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24 August 2023 at 08:38 #657719
Chris152
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@chris152
Thanks Robert (I also thanked you in my previous post, I should have thanked Noel in that one – apologies Noel!). That's interesting about 6-pole, I'll remember that for the future. And I guess I'll leave the Revolution setting alone – I thought maybe it was going to try running the motor at 2800.

One final question, I hope – am I ok to fit a regular NVR switch between the plug that's in the wall socket and the inverter? And if so, am I correct thinking that I can connect the earths within the switch using a simple block connector/ barrier strip?

Edited By Chris152 on 24/08/2023 08:38:56
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24 August 2023 at 17:42 #657778
Chris152
Participant
@chris152
ps – I was thinking of an NVR with emergency stop, which is more important to me than the NVR. Since my last post I've read inverters don't like power supply just switching on/ off, so it'd be an NVR switch with emergency stop, after wall plug and before the inverter. I'll use the control panel for starting/ stopping the inverter.

Something like this:
https://www.axminstertools.com/kedu-kjd17b-nvr-switch-230v-1ph-102532?utm_source=tag&utm_medium=affiliates&utm_content=2266&tagrid=58983622&glCountry=GB

Is that an option?

Edited By Chris152 on 24/08/2023 17:58:24

Edited By Chris152 on 24/08/2023 17:59:35
24 August 2023 at 20:07 #657802
Robert Atkinson 2
Participant
@robertatkinson2
Hi Chris.
You don't or should not need a NVR with a VFD. The VFD whould have a input for an E-Stop switch and a setting for the amount of active braking applied. This is much faster stopping than just cutting power on a standard motor. Just cutting the input to the VFD means it will take LONGER to stop due to the stored energy in the internal "bridge" capacitor(s).
There should also be a parameter to select if the VFD restarts on power-on. This should be set to NOT re-start on power on. The start and stop buttons need only be low voltage / current momentary switches.

You should have an isolator. If the power socket is eassily accesible then pulling the plug covers this. I like to put a IEC 60320 C13/14 "kettle lead" plug and socket on the enclosure so you can instantly see that it is unplugged.

Robert.

Edited By Robert Atkinson 2 on 24/08/2023 20:08:16
24 August 2023 at 22:52 #657815
Chris152
Participant
@chris152
OK, I've spent the evening reading and watching on how to set this up Robert – I've not sorted it yet, but things are slowly starting to fall into place, I think. By that, I mean I'm starting to understand how external controls are attached, tho the parameter specs are pretty confusing to me.

I've also realised, after reading another thread on here, that I need to create/ buy some kind of metal, ventilated enclosure for the inverter. So external controls become a must, I guess.

Thankfully I'm in no rush and quite enjoying learning all this, tho it doesn't come naturally to me.

Thanks again Robert.
24 August 2023 at 23:14 #657819
duncan webster 1
Participant
@duncanwebster1
I strongly suspect there isn't a lot of difference in the rotor and bearings of a 1500 and 3000 rpm motor, so I have no compunction in running a 1500 rpm motor at 75 hz. It hasn't done mine any harm.

Mine is set up for braking via the VFD, so it stops more quickly using the normal stop button, but I have a second Estop which cuts the power to everything, VFD, ELS etc. You never know, the VFD might have a fault which keeps it going even if you've hit the stop button. Unlikely I know
25 August 2023 at 10:23 #657872
Chris152
Participant
@chris152
Where did you place the second Estop, Duncan?

I think I've figured how to attach and program external on, off and potentiometer, following this link

**LINK**

(it covers both wiring and parameter setting clearly, which many don't), but am unclear about an emergency stop – is it any different from the normal stop? I'd really like one we could operate with a hip or whatever's nearest to it, so not a regular size button – I think they're called mushroom buttons?
25 August 2023 at 11:00 #657878
noel shelley
Participant
@noelshelley55608
One point to remember with some emergency stop buttons is they may latch ! This means that to reset the button must be turned to pop out – the circuit is now reset ! Noel.
25 August 2023 at 14:27 #657915
duncan webster 1
Participant
@duncanwebster1
Posted by Chris152 on 25/08/2023 10:23:26:

Where did you place the second Estop, Duncan?

It's on top of the headstock utilising a hole which I suspect was for a machine light mounting. It cuts off the mains supply to the vfd and to a 4 way adapter into which are plugged the low power things, DRO, ELS etc. I think ideally the Estop would cut supply to the main contactor, but I haven't got one. The Estop is not intended to regularly interrupt the power, it's there so if all else fails and I'm in panic mode I can switch everything off.

I did once spend an unhappy half hour trying to work out why everything was dead, yes I'd leaned on the latching Estop.

Edited By duncan webster on 25/08/2023 14:28:55

Edited By duncan webster on 25/08/2023 14:31:09
25 August 2023 at 21:05 #657978
old mart
Participant
@oldmart
I chose a 6 pole 1hp motor for the Tom Senior light vertical R8 conversion, it can reach 2000rpm, but has been programmed to no more than 1500rpm, which gives a maximum spindle speed of about 3000rpm, which seems a sensible maximum. The benifit of 6 poles is that it looses less torque at lower rpm which with the pulley combinations gives a really good range. I bought from the inverter supermarket and would do so again.
25 August 2023 at 21:08 #657979
Howard Lewis
Participant
@howardlewis46836
Failing to notice that I had somehow latched my E stop cost me time circuit checking until I msaw my silly mistake of leaning on the button!

"Experience lets you recognise the mistake the next time that you make it!"

Howard
25 August 2023 at 21:25 #657986
old mart
Participant
@oldmart
I have two e-stops on the Tom Senior, both latching and turn them both off to make it harder for unauthorised people monkeying with it. There is a window in the metal box that the VFD is housed in and NST (no start) shows when the e-stops are active and RDY (ready) when the green button can work.
25 August 2023 at 22:01 #657990
Chris152
Participant
@chris152
OK, progress of some sort, albeit perhaps a bit of a cop out. I discovered by accident, amid the day's searching for VFD connection info, an extension cable and mount for the control panel on the inverter – £12 delivered on ebay. With that mounted on a small tv lever arm which I have, and the inverter further away on the wall in a wall box, that's almost me sorted for the time being.

I'm struggling to find the emergency stop parameter, tho P58 ('Multi function input,' SP1), option 5 does say 'Emergency stop'; P12 ('Stopping modes' ) option 3 has 'Emergency brake' (alongside Inertial stop, Deceleration stop and Brake stop options); and finally, p50 (Multi function input 1 X1 binding post' ) seems to have option 19, 'Emergency stop' ('seems', as the layout is confusing and p51-55 appear to occupy the same space as 50).

So I'm confused as to which is the parameter I need to set – I'm assuming the Estop button is wired as per any external stop button?

Finally, reading around the net on metal enclosures for VFDs I read that the metal enclosure needs to be earthed – any suggestions as to which earth cable from the VFD connects to the box?

Apologies for so many very basic questions.

Edited By Chris152 on 25/08/2023 22:07:15
26 August 2023 at 13:11 #658060
Chris152
Participant
@chris152
A brief one –

Apparently the Estop switch for the VFD needs to be Normally Open. Is that because when activated, it completes the circuit and sends a signal to the VFD to operate the brake?

Looking at Eswitches online, some are NO/ NC, and inside have one pair of contacts marked NO, the other marked NC. Will I be wiring to just the NO pair (3 and 4) and leaving the NC pair empty? Here's an example switch:

Link

I can't find a parameter that indicates that the power won't return to the motor once the Eswitch is released, so assuming the programme requires pressing the start button to get going again. We'll see.
26 August 2023 at 15:14 #658067
Robert Atkinson 2
Participant
@robertatkinson2
I can't comment on the paramrters as I don't have the same model drive.
The mains earth coming into the enclosure should go to a earth stud on enclosure and a separate earth lead goes from the same stud to the earth termainal on the VFD.
If the enclosure does not have a built in stud. use a 4mm bolt. don't forget to remove any paint under it. Use one nut to secure the bolt through the enclosure wall and a second to secure the earth cables. Ideally use ring tags.

For the E-Stop, yes just use the NO contact.

Robert.
26 August 2023 at 15:29 #658070
Chris152
Participant
@chris152
That's great – thanks Robert.
27 August 2023 at 18:56 #658236
old mart
Participant
@oldmart
VFD's can be programmed for switches to work both ways, my two e-stops are in series with the normal stop button. The VFD is set for normally on, and to stop when the circuit is broken so all three switches have to be set at normally on for the motor to work. I have used two e-stop switches as they are much more prominant than the stop switch and also latch off. One is on a mag base and extension cable so it can be set in a position suitable for the particular work setup.

Edited By old mart on 27/08/2023 19:00:13
28 August 2023 at 07:56 #658261
Chris152
Participant
@chris152
Thanks old mart, I had a hunt through the parameters but couldn't find anything relating to NO/ NC, so best work with it as is I guess. Magnetic base for the Estop sounds useful, I'll take a look

The earth connection on the inverter is already really crowded with two wires connecting and I'll struggle to get a third in there (it's very small) so I was thinking an oversize (40 x 30 x22cm) flame retardant ABS enclosure would be easier as it needs no earth. I know it won't transmit heat as a metal case would but we only use the lathe for short periods of time and it'd be an option, with the inverter well away from flying chips, to open the door if we needed to use it longer. Plus we could easily drill a few holes and cover with mesh to keep insects out. Any other reason not to use a plastic enclosure?

Edited By Chris152 on 28/08/2023 08:03:03
28 August 2023 at 10:00 #658274
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Chris152 on 28/08/2023 07:56:13:

Thanks old mart, I had a hunt through the parameters but couldn't find anything relating to NO/ NC, so best work with it as is I guess. Magnetic base for the Estop sounds useful, I'll take a look

The earth connection on the inverter is already really crowded with two wires connecting and I'll struggle to get a third in there (it's very small) so I was thinking an oversize (40 x 30 x22cm) flame retardant ABS enclosure would be easier as it needs no earth. I know it won't transmit heat as a metal case would but we only use the lathe for short periods of time and it'd be an option, with the inverter well away from flying chips, to open the door if we needed to use it longer. Plus we could easily drill a few holes and cover with mesh to keep insects out. Any other reason not to use a plastic enclosure?

…

Don't overcrowd the earth terminal : one big wire with an eyelet is best. The problem is dealt with by an earth block like this example from Screwfix:

Ideally the block is bolted to the metalwork near the VFD, but it can be free-standing. The main requirement of earthing is that all connections be secure – you don't want earth wires vibrating off an overcrowded terminal screw. Insulated terminal blocks are available too:

ABS if you must, but metal cases are stronger, fireproof, and shield Radio Frequency emissions. An unfiltered, unshielded VFD is a potent source of electrical filth. Putting the VFD inside an earthed metal box helps contain its anti-social output.

Dave
28 August 2023 at 10:45 #658282
Chris152
Participant
@chris152
Aha, I'd not seen an earthing block before. All clear.

Would the correct thing now be to remove all the connections from the inverter and recut them, leaving extended earth cables and the other cables normal length, allowing the earths to connect to the block/ enclosure?

It'd be easier if I could post pics when trying to explain things – do I need to find a photo hosting site and put them there, then link to them from here in my posts? I'm sure there's a guide somewhere on here, I'll take a look now.

Thanks.
28 August 2023 at 10:49 #658285
Chris152
Participant
@chris152
Got it!
28 August 2023 at 12:45 #658298
Emgee
Participant
@emgee
If you are going to earth the cable screens at the VFD you need to use the correct earth bonded gland or other suitable arrangement.

Emgee
28 August 2023 at 13:07 #658301
Chris152
Participant
@chris152
I didn't even think of earthing the screen wiring. I've just searched earthing gland and see it can be an earth tag or gland – presumably this connects to the same earthing block that will be attached to the metal wall enclosure, and that the cable earths attach to before connecting to the inverter?

Thanks for pointing this out.
28 August 2023 at 13:32 #658304
Robert Atkinson 2
Participant
@robertatkinson2
A metallic case also reduces interference. You can use an ABS box but you should fit the VFD and any filters onto a metallic plate that is then installed in the ABS cox. All earths, includng cable screens / armour, should be connected as directly as possible to the plate.
With plastic box the best way to cround the screen is with a metallic clamp. You need 360 degree contact. Even an inch or two of tail reduces the effectiveness of the screen.
If your VFD does not explictly have an EMC filter you should fit one. it also needs to be mounted on the plate.

Ther are two disadvantages to putting the E-Stop in series with the normal stop input:
1/ The machine will not stop as quickly.
2/ if ther is a fault in the normal stop circuit the E-Stop won't work either.

Robert.
28 August 2023 at 14:55 #658307
duncan webster 1
Participant
@duncanwebster1
Mine stops more quickly using the normal stop as that brakes the motor electrically. Using the Estop to cut all power means that it will stop no matter what the fault.
28 August 2023 at 15:10 #658309
Chris152
Participant
@chris152
I'm now more or less decided we'll use a metal box.

Concerning EMC filter – the description of the inverter states:

"PWM CONTROL:
By optimizing PWM control technology and electromagnetic compatibility, it satisfies users' requirement of low noise, low electromagnetic interference."

Under the specs, it says "Filter – Fitted", but it doesn't specify what kind of filter.

Is that sufficient to control EMC or should I fit a filter?

Thanks.

Edited By Chris152 on 28/08/2023 15:18:34
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