Will a 220v to 110v stepdown transformer like this cause noticeable Electro-Magentic Interference?

[Rjdnfnfn]

I hired an electrician to do some electrical work for a job I am at. I put in the SOW that I wanted the stepdown transformer installed in a seperate enclosure, but he did this instead. Not only is this more hazardous, but it could cause interference since things like transformers are well known for making EMI.

 

[Smilingreen]

Not sure why he decided to use a Machine Tool transformer? I can't read the label real well, but chances are, your 48VDC power supply would have accepted 220VAC as a input voltage. That would have eliminated the need for a transformer. Most din rail mounted power supplies can do this, now days. But, as far as a hazard, they make finger safe, snap on terminal covers for transformers. That would have eliminated a possible hazard around the transformer. EMI can be greatly reduced by simple wire routing practices. Don't run CAT cables parallel with power cables. Use shielded CAT cables.

 

[TonyR]

+1^^.
I'd be even more concerned if the pole is for 208 or 220VAC street or parking lot lighting with no neutral and if so.....how'd he derive that white neutral that's on the 120VAC input to the 48VDC power supply? Surely it's not tied to the pole along with that green conductor........

FWIW, I don't think a 240 to 120VAC stepdown xfmr will be a big EMI issue as it is being deployed there....that being said, if you put something in the plans/specs (like the separate enclosure) and he failed to follow, I'd hold his feet to the fire.

 

[Smilingreen]

+1^^.
I'd be even more concerned if the pole is for 208 or 220VAC street or parking lot lighting with no neutral and if so.....how'd he derive that white neutral that's on the 120VAC input to the 48VDC power supply? Surely it's not tied to the pole along with that green conductor........

FWIW, I don't think a 240 to 120VAC stepdown xfmr will be a big EMI issue as it is being deployed there.

One would hope he grounded the neutral wire coming off the secondary side of the transformer. Hopefully, the backplate is bonded, also.

 

[TonyR]

One would hope he grounded the neutral wire coming off the secondary side of the transformer.

I installed a transformer and a 120VAC GFI outlet on a 240VAC parking light pole to charge a speed radar in a police dept.'s parking lot once; ran a neutral about 50 ft. to a panel so I could tie one of the transformer's secondary legs to the panel neutral, the pole had a ground rod in its foundation for the protective earth ground.

 

[Rjdnfnfn]

Unfortunately the stepdown was required for the smart PDU. I think I will just get the electrical contractor to redo it since they made me go through a lot of BS by creating an account with them just to do one small job.

 

[BORIStheBLADE]

At one of my campus at the base of light poles with cameras they have installed this kind of transformer. They have ran 277 and 480 as primary feeds to these transformers and I haven't heard about any EMI. I don't know for sure if its just the transformer creating the EMI. I'm wondering if all that stuff in the same box could be the issue?

 

[Rjdnfnfn]

At one of my campus at the base of light poles with cameras they have installed this kind of transformer. They have ran 277 and 480 as primary feeds to these transformers and I haven't heard about any EMI. I don't know for sure if its just the transformer creating the EMI. I'm wondering if all that stuff in the same box could be the issue?

I guess I will fire it up and then let it run for a few days with network monitoring tools and see if there are problems. Maybe I can install shielding around the transformer and re route the cables to avoid close contact with it.

 

[TonyR]

I guess I will fire it up and then let it run for a few days with network monitoring tools and see if there are problems. Maybe I can install shielding around the transformer and re route the cables to avoid close contact with it.

Frankly I'll be surprised if you read anything of real consequence.

Now if the primary AC voltage frequency was much higher than 60Hz or if the transformer primary was being rapidly switched off/on then the subsequent field collapsing of the primary or secondary may, respectively, impress back EMF and/or healthy spikes on the line.

 

[alastairstevenson]

Maybe I can install shielding around the transformer and re route the cables to avoid close contact with it.

You'll get more high-frequency EMI mush from the switched-mode power supply than from the mains-frequency magnetic field of the transformer.
They can be pretty bad for that.
Just pass a small loop of wire around a switched-mode PSU and observe the pickup on an oscilloscope and you'll be amazed.