3 phase - radio puzzle

I have a old shortwave receiver in the shed, normally on the 20 meter amateur band. I noticed the other day when i powered up the vfd on the mill, it sent the receiver haywire, couldn't hear a thing.

The spec should be written on the cable sheath.

My compressor has a screened power lead with a clear sheath so you can see the braided shield.

So it is sounding like I need a filter at the inlet but not knowing what type/spec of filter I need I would appreciate some guidance at what I should be looking for.

Thanks

Ron

Look for IEC (International Electrotechnical Commission) EMI (Electro-Magnetic Interference) power line filters, about £10, they plug in, you don't need to open them up.

Businesses that sell VFDs often also sell suitable filters and should be able to advise.

I would recommend speaking to Inverter Drive Supermarket. When I did my 3phase conversion on my lathe, they were incredibly patient in specifying a solution and answering my novice questions, all for a single one off order.

Hi Ron,

What is the full model number of your CUB VFD? With that information I can recommend a suitable EMI filter.

The manual can be downloaded here https://inverterdrive.com/file/IMO-Jaguar-Cub-Manual

Robert G8RPI.

Hi Robert, thanks the model number is CUB3A-1

Ron

Hi ,

The Ideal solution is a two stage block filter like this

uk.farnell.com/corcom-te-connectivity/3eq1/filter-3a-1-phase/dp/9586210

But they are not cheap .As Geoff suggests a IEC mains input connector with built in filter is a lower cost ooption. It also has lower perfomance but one like this

uk.farnell.com/epcos/b84771m0006a000/filter-inlet-iec-medical-6a-250v/dp/2317950 should cure your problem and provide a handy inlet connection.

I could dig out a used filter if you don't want to order one.
Is your VFD in any kind of enclosure?

Robert G8RPI.

Thanks for this Robert, really helpful. No my VFD is not in an enclosure, it is mounted on a bracket under a shelf with space all around it, it is out of the way of swarf/coolant and in a clean area.

Ron

I find it odd that the issue is still present on different bands and only on one radio , are any of the radios the same brand and model ? Does the offending radio do the same if you change bands and frequencies? Does the interference change pitch in tune with the vfd setting?

I’m asking this because i am curious as to where the signal is getting into the receiver , if you can tune it out it is via the antenna / tuning circuit and if not maybe via the IF or audio sections that may not be screened properly .

Either way you are producing some EMI which needs to be addressed .

I had a problem recently with a couple of dab radios , every time i would turn on my switchmode power supply they would go insane if they were any closer than a few metres away from it .

The IMO part can be found here **LINK**

Thanks guys for your help and suggestions, I will order the cheaper EMI power line filter as suggested by Geoff and Robert and give that a try to start with.

Ron

Similar to my experience, found that the cable sheath had come away from the earth point at one end!

Hi,

The issue is present on two different radios on different bands but only in one of two locations. The oddity is that it's the location remote from the VFD that has the problem. see my earlier posts.

Robert G8RPI.

Generally if you have a VFD with fitted filter it will trip your RCB which is why a lot of suppliers sell them without for home use.

regards Martin

Not had a problem with mine fitted with a filter and property on RCBO's on each individual circuit.

I think you said one radio was a battery one. It might be interesting to use it as a detector and walk around the garden and house finding the hot spots. If it is ok in the middle of the garden and you run an extension lead out to it does that bring the interference with it.

Hi guys,

Just to sum up, all the radios are battery operated and all tuned to BBC Devon, though I have tried the channel on both MW and FM. I have tried a radio in the bathroom, in the bedroom, the workshop, the lounge and the kitchen and all are fine except for the one in the kitchen. I have just thought of something though, the electric comes into the property in the kitchen, on the end wall are the meters / consumer units etc, is that where the problem is i.e. the kitchen radio been in close proximity to those.

As well as the EMI power line filter I have ordered, would there be any benefit in fitting Ferrites to the motor cable. I watched an American video last night and a power line filter cured the problems that a guy had in his workshop. He then fitted ferrites to the motor lead simply because he had them in the drawer but when measured with good equipment the ferrites reduced the interference levels even more, just wondered..?

Ron

Hi Ron,

You appear to have a similar setup to mine. I have fitted the VFD in a die cast box with a EMI filter as described by Robert A and ensured a good ground/earth from the motor and remote controller. I have not had any EMI or EMC issues. Checked with my SDR as spectrum analyser small amount of noise was detected.

If you fit the VFD in case make sure it has good heat sinking qualities.

Hugh