Preventing mains contamination from PWM DC Motor Controller

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stebbo

Member
Location
Sydney
Situation: household treadmill taking out DSL internet when motor running.

A bit of research on it has revealed it's quite a common problem. Noise from the chopping back into the mains, mains acts as an antennae throughout the entire house and it's picked up by the phone lines. I even read one case where the neighbor's treadmill was taking down his internet.

I called a well-known manufacturer of surge protectors/isolators as to what exactly I'd need but generic support staff just tell you the obvious.

Any suggestions as to what is needed?
 

robbietan

Senior Member
Location
Antipolo City
Situation: household treadmill taking out DSL internet when motor running.

A bit of research on it has revealed it's quite a common problem. Noise from the chopping back into the mains, mains acts as an antennae throughout the entire house and it's picked up by the phone lines. I even read one case where the neighbor's treadmill was taking down his internet.

I called a well-known manufacturer of surge protectors/isolators as to what exactly I'd need but generic support staff just tell you the obvious.

Any suggestions as to what is needed?

equipment grounding comes to mind. a faulty grounding system may result in the mis-operation of sensitive electronic equipment.

otherwise, a filter or a choke coil on the line side of the PWM may lessen the problem.
 

stebbo

Member
Location
Sydney
I can't fully answer your question because the technical aspects of your problems are not in my real of expertise, but I would think a UPS backup device would solve this problem. I have a a few UPS's for my computers and surveillance system to eliminate line interference like this.

http://www.newegg.com/Product/Produ...m_sp=ProductSpotlight-_-42-102-070-_-06012011

The interference is being picked up in the phone line, causing errors on the dsl connection so powering the modem off the UPS I can't see solving the problem. Or do you mean running the treadmill off the UPS? That would provide isolation I guess, but they'd have to be simpler way. The treadmill has a 3.5HP motor in it, that's a getting quite expensive for UPS. Thanks for your thoughts.
 

ELA

Senior Member
Occupation
Electrical Test Engineer
With noise interference the first questions to answer are:
Is the noise radiated (broadcast through the air) or conducted through the wiring , or both?

The interference most likely starts out as conducted noise and then radiates from the home wiring into the phone lines.

You need to stop the noise at the source. First make sure you have a good ground and then add an EMI filter as close to the treadmill as possible.
 

kwired

Electron manager
Location
NE Nebraska
The interference is being picked up in the phone line, causing errors on the dsl connection so powering the modem off the UPS I can't see solving the problem. Or do you mean running the treadmill off the UPS? That would provide isolation I guess, but they'd have to be simpler way. The treadmill has a 3.5HP motor in it, that's a getting quite expensive for UPS. Thanks for your thoughts.

Maybe getting a treadmill would be the best solution, and may cost the least. You can still charge customer for figuring out the problem or tell them how much more it will cost to fix what is there.
 

stebbo

Member
Location
Sydney
equipment grounding comes to mind. a faulty grounding system may result in the mis-operation of sensitive electronic equipment.

otherwise, a filter or a choke coil on the line side of the PWM may lessen the problem.

I checked the grounding on the treadmill and all seems intact. I guess the grounding in the household wiring could be amiss but I've tried it on two sub-mains with similar results.

I bought a Belkin filtering power board today, it supposed to contain power contamination within it. It seems to have helped as you suggest above, the internet is functional at least although at about half the speed as normal. Need to do some more testing though.

It definitely looks like the interference is coming through the phone line. There is a 10 inch concrete slab floor lined with galvanized iron between the modem and the treadmill so I've ruled out interference radiating from the treadmill through the air.

Frustrating. Cheers.
 

kwired

Electron manager
Location
NE Nebraska
How often is this treadmill used that it is such a problem? Or do they use web videos or music while excersing?

What equipment is connected to phone line? maybe something on the line is what is picking up interference. Most premises phone wiring should be twisted pairs to help reject interference. The cord from the phone to the phone jack is not typically twisted. If they have a long extension of this type it could be an antenna for the phone system.
 

stebbo

Member
Location
Sydney
With noise interference the first questions to answer are:
Is the noise radiated (broadcast through the air) or conducted through the wiring , or both?

The interference most likely starts out as conducted noise and then radiates from the home wiring into the phone lines.

You need to stop the noise at the source. First make sure you have a good ground and then add an EMI filter as close to the treadmill as possible.

Yes, I totally believe what you're saying is the case, that it enters the mains from the treadmill and radiates into the phone line. The treadmill has about a 10 foot power cable that I've plugged into the EMI filter I brought today. Half fixed. Radiation through the air I've pretty much ruled out due to a dividing concrete slab which severely attenuates WiFi frequencies passing through and a few crude experiments like encasing the PWM board in a cast iron dutch oven :))) and listening with an AM radio. The modem is powered by a DC adaptor so can't really visualize noise being passed through it to cause sync problems.
 

stebbo

Member
Location
Sydney
How often is this treadmill used that it is such a problem? Or do they use web videos or music while excersing?

What equipment is connected to phone line? maybe something on the line is what is picking up interference. Most premises phone wiring should be twisted pairs to help reject interference. The cord from the phone to the phone jack is not typically twisted. If they have a long extension of this type it could be an antenna for the phone system.


The treadmill is used for 5-12 hours per day as part of walk-while-you-work office desk, so reduced internet speed is an issue.

The phone line has a single phone connected with a 6 foot cable to the wall jack via a DSL line filter. The DSL modem is the only other equipment on the phone jack, again about a 6 foot cable. I might check the wall jack where the modem is connected tomorrow now that you bring it up, it looks to be an afterthought, possibly home handyman and might not be twisted.
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
The treadmill has about a 10 foot power cable that ...
PWM variable speed drives often use line reactors to minimize similar problems.

I don't know what you are allowed by your local codes to do.

First, is the power cable shielded? If not, are you allowed to replace it with another which is? Could the cable be disconnected and be run inside a flexible metallic raceway with a good ground?

Second, can you put your filter IN the treadmill housing; that 10 ft cable is a pretty good antenna for some frequencies.

Filters are often not symmetrical ... there is a line side and a load side. I'm not sure the device you have is optimized for oyur situation; but not many consumer devices will be.
 

stebbo

Member
Location
Sydney
Maybe getting a treadmill would be the best solution, and may cost the least. You can still charge customer for figuring out the problem or tell them how much more it will cost to fix what is there.

This is happening with a commercial treadmill I've purchased primarily to estimate motor loadings in order to develop my own range of office treadmills. The interference issue was totally unexpected, but crucially important I understand and eliminate it if I'm to pass local EMI compliance testing and provide a product that doesn't cause people issues.
 

stebbo

Member
Location
Sydney
PWM variable speed drives often use line reactors to minimize similar problems.

I don't know what you are allowed by your local codes to do.

First, is the power cable shielded? If not, are you allowed to replace it with another which is? Could the cable be disconnected and be run inside a flexible metallic raceway with a good ground?

Second, can you put your filter IN the treadmill housing; that 10 ft cable is a pretty good antenna for some frequencies.

Filters are often not symmetrical ... there is a line side and a load side. I'm not sure the device you have is optimized for oyur situation; but not many consumer devices will be.

The power cable is a standard IEC power cable so easily disconnected. I can't say I've cut one open recently but I bet it's not shielded. Good point.

The device I purchased primarily because I read it cured a treadmill users woes with his wired internet also going down. But I can appreciate every set up is different.

The literature on the filter power board says it contains power contamination within it so I'm assuming that it both stops noisy power being delivered to devices plugged into it as well as noisy devices plugged into it contaminating the house wiring. But it's hard to get a helpful answers from the manufacturers.

I see if I can track down line reactors in the code.
 
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