5000 cars cause AM interference

I wanted to post about a random issue I’ve discovered now that the Red Line is running again. Whenever I get close to a set of 5000 cars along the Dan Ryan, I get a humming which overpowers any AM radio station I happen to be listening to. I’ve had it happen in two different cars, and on every AM station I’ve tried. The other day I was sitting in traffic, and “heard” the train approach from quite a distance behind me and then the noise went away after it passed. Any idea what it could be? The lighting system perhaps? I think it is also happening at the newly renovated stations but I’m not for sure yet.

Chuck

INteresting you note this - the 1500DC on the IC used to cause total problems with a factory nextdoor that used radio control cranes in the plant. We had to eat a lot of money in troubleshooting that one, and then eat an entirely new wireless system before I figured out what it was.

It could be the inverters that power the AC traction motors. Does the hum change in pitch and/or timbre?

spRocket wrote:It could be the inverters that power the AC traction motors. Does the hum change in pitch and/or timbre?

After hearing it a couple of times, it is more of a ringing than a hum. Imagine hearing the ringing bell from a freight train under a radio broadcast. I suppose the traction motors seem to be the likely culprit, it's just strange that I get zero interference from the older train sets?

Chuck

Older trainsets are not AC with inverter control. They're DC motors with analog control - resistors and contactors. I bet the hum you hear is awfully similar to the sine wave hum that you hear from an electric traction motor when starting/stopping.

I've been on the Dan Ryan twice in the past weeks, listening to AM radio, and there was no interference.

AC inverters are about the best EMI generators ever invented. Actually, they're pretty much the best way to turn electricity into annoying noise, period. Harmonic filters help, somewhat. The newer drives are a bit better than the older ones - there's also some leeway in the setup that can help out.

My company did a pumping station once where the old GE drives (REALLY old ones, actually out of Erie, I think) were replaced with newer ones (Eaton), when the station was transferred over to the new drives, the folks in the office next door popped their heads in, wondering if the pumping station was being closed down - it was THAT much quieter. Old drives you could hear a block away. New ones you could stand next to the pumps and carry a normal conversation...

Interesting you mention that - the new Metra and South Shore bilevel cars are almost silent while the 10-year old South Shore 100-series cars are fairly loud.

Phil, did you ever work on Thor drives? I never had the pleasure but some of the older guys I used to work with told me horror stories of trying to program them in an effort to replace 5-speed crane controls or static stepless.

No - I never saw them. The bulk of what I've seen have been ABB, GE (Fuji rebadge, and the lone weird thing from Erie), Telemechanique, AB, Siemens (yuck) and Eaton. And a few Benshaw softstarts. Previous employer used a lot of Delta and Mitsubishi.

Older drives tended to be less, err, full featured than current ones. I'd be surprised if anyone had any trouble integrating something made in the last 5 or 10 years. Today's drives pretty much do everything but program themselves, and I'm sure ABB will have that one figured out next year...

We're also typically 4-20ma loops and hard contacts - if a well runs at 52.3 hz instead of 52.2hz, it's ok. Though we did have one where we used Profibus to link something like 20 drives to a PLC. BTW, Profibus sucks....