2 pole or 4 pole for Myford ML7R

Both wires I have are stranded.

I don't recall the size of the mains input wire, but just measured the diameter as about 1.8mm, which makes it about 2mm2 - but that doesn't seem to be a standard size, so I'm measuring wrong! But clearly it's at least 1.5mm2.

The three phase wire is 2.5mm2.

So I'll use 13A. I'll look into the remainder of your last sentence and see if I can understand (as you've gathered, I really don't know about electrics at all)!

Thanks Robert.

Robert is correct in his comment and I had made the fatal mistake of assumption - that in wiring up a machine tool one would use at least 1.5 flex or cable. I tend to use 2.5 flex but that is because I can, though things get tight in some 13a plugs !

Chris, to find the sectional area of a wire or flex take 1 strand accurately measure the diameter in mm then use the formula Pi R squared. If a single conductor then that will be the answer, if flex then multiply the answer by the number of strands. Since in the main there are standard sizes of flex or cable if the answer looks near it should be right - or way out and obviously wrong ! Good luck. Noel.

Thanks Robert - I'd remembered Pi x r2 from O-Level maths in my approximate calculation, quite surprised myself!

I'm trying to figure the parameters I need to set and would appreciate any advice:

1. Maximum operating frequency is preset to 65Hz - should I change that to 50Hz here in the UK? (A separate parameter says 'Working Frequency - Default 50Hz.'

2. Revolution for 50Hz is stated as 2800 - as this is 4-pole, should I change this to about 1500 for mine? (I've read around the net and some parameter specs for XSY AT1 specify 2, 4 or 6 pole, this doesn't appear in my handbook, will it be automatic?)

I can't find any others that look as if they need changing at this stage, let me know if anyone thinks I'm wrong?!

Edited By Chris152 on 24/08/2023 07:25:01

I'd leave the maximum frequency (speed) at 65Hz. This gives you a bit more operating speed range but is well within the limits of your 50/60 Hz motor. As an aside, often the best utility can be had from a motor/VFD set up by arranging for the motor to run at higher speed than it's name plate rating. This is why I recommended, and fitted on my own ML7, a 6 pole motor. On a VFD this motor can easilly run at 4 pole motor speeds. It has the same rotor, bearing and fan construction as the 4 pole. It prodces more torque at low speeds than a 4 pole. I also fitted a larger motor pulley to reduce stress on the belt.

The revolution for 50 Hz probably only affects the RPM indication or parameters set in RPM. It should be set to the value for your motor but does not affect actual operation of the motor.

Robert.

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

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

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

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.

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

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?

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.

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

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.

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

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.

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

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.

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.

That's great - thanks Robert.

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