If all else fails, feed the inverter via suppressed power socket . Hopefully, this will prevent the replacement from sending any nasty spikes back up the mains.

Don't know what my inverter does in the way of EMI, since it has always been fed from such a socket, and there have been no problems seen or reported..

Howard.

Contact Newton Tesla about sending it back as not fit for purpose / defective.

Mmm, not sure abt that…It all depends…Most reputable VFD suppliers manuals give reasonable guidelines towards appropriate installation. Generally this includes size and max lengths of wiring, routing guidelines for the wiring from VFD to motor, etc. Are such guidelines in the NT VFD manuals and have they been reasonably adhered to?

Almost all cases of excessive LOCAL EMI from VFD's stems from the wiring from VFD to motor – not from VFD to mains supply. The level of EMI in the wiring tween VFD and Mains plug is orders of magnitude less that in the wires to the motor.

The motor wiring carries 400volt peak, PWM switched voltage, with very fast rise times and high peak currents – these currents can be 2 to 10 time the RMS current flowing in the motor winding circuit. It is precisely those PWM volts/currents that are the culprit in most cases. The mains side is supplying said current peaks as well, but the mains is converted to DC inside the VFD and feeds large electrolytic and Mylar or Polypro capacitors. These do a not to shabby job of filtering out most of the serious peaks, leaving the mains lead EMI 'tolerable' for home workshop applications.

If you route the motor wiring circuit at all near the DRO circuits, you will have trouble. It you have long wire lengths you increase the radiated EMI field greatly. The wiring is the antenna and the bigger the antenna, the further the filed can reach.- 1 meter of wire between VFD and motor should be an easily achievable limit ( try for less), grouped tightly together, away from all DRO or other machine electronics, and if still a problem, enclose the motor wiring in a shield – the outer braid from some heavy coax cable, copper or aluminium tape wound around the wire, and ground the VFD end to the VFD ground.

Joseph

Good points with which I entirely agree with for a VFD box bought as a stand alone unit for customer installation.

However Newton Tesla supply the motor, inverter and pendant as a complete kit with all wiring save for the power input to the VFD. As such the EMC issues should have been dealt with as bought and no problems ought to occur so long as the VFD to motor wiring isn't modified or, if not already pre-wired, not installed as per the instructions.

If the controls are on a separate pendant it would seem to take some seriously misguided creativity to get the VFD and its output wiring close enough a reasonably made DRO box for it to be affected by radiated EMC.

Obviously given the price / performance limitations of anything sold on the consumer market there will be edge cases where ambient sensitivity to EMC may be such that a normally acceptably low level of emissions may still be too high making extra filtration and installation precautions needful.

Lathe plus DRO is pretty much standard these days for anyone whose pockets are deep enough to buy an off the shelf motor and VFD kit. So it should just work.

Newton Tesla have earned a decent reputation for supplying workmanlike equipment so it sounds as if something is seriously wrong.

SOD

Having had some experience with sorting EMC issues back in the days when it first became a thing it really isn't something where individual experimentation beyond simple cook book add ons is likely to be rewarding. Bottom line is that the rules for decently well behaved equipment design are now well established as are those for proper installation.

A kit of decent quality equipment from a reputable supplier should  "just work" unless there is something seriously odd going on or if you want to use it for duties its not made for. This is a bread and butter product for Newton Tesla and the expectation is that any EMC issues will be minor and associated with something unduly sensitive. Modern DROs should cope with any emissions from a reasonably positioned VFD just fine.

Clive

Edited By Clive Foster on 17/04/2022 16:36:20

As far as I recall the EM noise emissions allowed for industrial installed equipment is far more that that allowed for Laboratory/Domestic installation. So Newton-Tesla may say their kit is designed for industrial installation. To meet domestic requirements they may say you need to buy a filter. An extremely crude filter can be made by simply winding the mains lead around a lump of steel rod and this may be sufficient to prove that conducted EM noise is causing the issue with the DRO.

CS

REO UK Ltd Filters are a good point to start with (if you have to)

/www.reo.co.uk › emc-filters1

I've recently installed the same setup and had no problems with interference. Did find NT very helpful (and quick) in sorting a couple of other minor issues.

I agree with some of the replies in that you should first check the earthing of everything, cable routing etc to eliminate the obvious. If all Ok, what about lashing up a temporary 'faraday' metal screen box for the inverter to see if that improves things and if it does you can build / get a proper one later?

regards Mike

.

The items shown on this page would appear to fit the description “kit”

**LINK**

https://www.newton-tesla.co.uk/product-category/lathe-speed-controls/inverter-motor-packages/

“ … for you to build into your own system.”

MichaelG.

Indeed, and a dialogue with Newton Tesla, who I've found to be most helpful, would seem more appropriate than sending it back as not fit for purpose.
This is particularly so, as they also advertise a fully pre-wired kit, which they state is "EMC / CE Compliant. Designed and manufactured here in the UK."
I have one of these on my Warco 720 (Myford S7 clone) and it works well; I've not noticed any interference on other kit or the radio.
https://www.newton-tesla.co.uk/product/av750-1-0hp-package-for-myford-super-7-raglan-mk5-boxford-aud-cud/

Bill

Thanks peak4,

We still don’t know what the kit included (not from the OP, who is the only important source of info). I’m not into guessing if someone has cobbled together a possibly dangerous arrangement.

IIRC, one recent wiring error included using an earth connection as a neutral – or something like that.

Possibly the opening line should have read ‘I have tried to’?

I had to earth both ends of the shielded cable on mine.