Motor Hum

Model Railroader Electronics and DCC
1

Hello;

I have a low hum in a can motor in a brass engine at low speed. The decoder is a Soundtraxx Tsunami. Any hints as to which CV’s to adjust that may help?

Thanks in advance.

Mark

2

Perhaps it motor is receiving AC current. Does it sound like a 60 cycle hum?

ROAR

3

Mark,

Two types of hum are possible – electical hum and vibrational/mechnical hum. Is this a recent conversion? If so, did the motor have to be isolated before/during the conversion? Or was the hum not present with the Tsunami already installed and now is?

4

Mike;

Good questions. I did not notice the hum when I operated on DC, though in all likelihood, if it was there I would not have noticed it. It is a brand new conversion to DCC. I believe it is an electrical hum. Need to be pretty close to notice it and at low speed. My concern is that I may be doing damage if I continue to operate that way.

Thank you,

Mark

5

Mark,

if this is „electrical“ hum, then it is very possible it is caused by BEMF motor control. Hum to some extent is normal, and it depends on motor but also on CVs that are related to motor control.

In general, if you decrease BEMF intensity (Soundtraxx calls it „load compensation“), motor hum should decrease.

In fact, you can fine tune “load compensation” to achieve best possible running at low speeds. You can use this procedure:

http://mrdccu.com/curriculum/soundtraxx/tsunami.html (go down to “I Can’t Get My Loco to Run Well Slowly“)##### I used this procedure, but in addition to that, in most cases I also decreased CV 212, because rarely it is necessary to keep it at value 255.##### While fine tuning, mute the sound with F8 and LISTEN to motor in very low speed steps. While changing different CVs you will notice that hum changes too
6

Open frame and coreless motors can be a real @#$@# for DCC decoders to control due to current surge issues. They are more prone to overheat as well.

Of the decoders available on the market, Lenz (non sound) is regarded as the best in terms of these types of motors. They even have a parameter allowing you to specify the type of motor you have to adjust feedback parameters. However LokSound also does very well in controlling those old motors.

7

Loksound also has a motor type CV - actually, most of the Euro decoders do, because I’ve also worked with CT and Zimo decoders and they have such a setting as well. Really does make a difference when set to the suggested range for each type of motor, even an old 3 pole motor can run well.

–Randy

8

Mark,

You getting some good advice here. The procedure Hrvoje referenced is part of a sheet of info on sound and slow speed adjustments I’ve collected for the Tsunami. I’ll tack on the rest of what I have below this. It is oriented twoards steam, but there are similar diesel “cheat sheets” out there, too.

Since yours is a new install, it’s possible that there may be something the motor is pressed against, trasmitting motor noise to the boiler or elsewhere on the shell via mechnical means.

Either way, I doubt you’ll damage anything, but it can be irritating. Here’s the rest of my collected wisdom, these excerpts from Steve Hatch and Jim Betz. Because of the complex nature of the interaction between many variables, they’re all slightly differents ways to achieve similar results.

Steve Hatch wrote:
Tsunami Steam CV Settings [Note: These set

9

I made the experiance that a low hum of the motor at low speed is a signal of a hard working motor powerful forced by the decoder to overcome a (small) mechanical problem. You can test that easy by switching BEMF off and run the engine at low speed. It should run as smooth as with enabled BEMF.