Large Scale Central

Why are power packs with pulse modulation bad for some brands of

Electronics Power and Sound
#1

Hey Y’all;

After looking at the 13 pages for this topic, did not see subject heading sounding like it would answer this question -

Why are power packs with pulse modulation bad for some brands of motors in G scale locos?
All the manufacturer’s paperwork says is that it is, there is no why.
For example, the HLW 4-4-0 I got last month. Apparently Bachmann loco is okay with it.

I come from scales and gauges where they have been the norm for 3 decades and don’t understand why they have suddenly become bad.

#2

Its not the motors. Its some of those fancy DCC and/or sound chips that have issues.

-Brian

#3

Well, in the HLW directions, it did specify the motor, and there is no sound system or DCC in it.
Not even a smoke unit.
Those are all purchaser provided and installed, if desired.
http://www.h-l-w.com/Products/Manuals/440%20Manual.pdf

Quote:
[u]Motor and Power Specifications[/u] Your HLW Locomotive is equipped with a 12 V DC precision, industrial-grade motor. The motors are mounted in a weather resistant housing and are intended to be waterproof. We recommend using a 2.5 amp power pack with variable speed control. Avoid using "pulse power" as it will eventually harm your motor.
#4

Whilst generally the caution is for the electronics associated with electric locos, it could be the motors depending on the sort of motor and the pwm frequency.

When you burn energy you generate heat.
In the case of Linear filtered DC, that heat is generated at the output transistor and requires heat sinking.
In the case of PWM the heat is generated in the motors.
It is best that for regular iron cored motors that the motor is open to the air for cooling purposes. Most LGB motors are sealed in plastic boxes.
AristoCraft, USAT and some Bachmann motors have air vents in the motor blocks.
So called core-less instrument motors cannot dissipate the heat as well as iron cored motors.
According Faulharber it is OK to use pwm with coreless motors provided the PWM frequency is over 5 KHz.

Then you have “Pulse” power which is different from PWM.
Pulse power usually means injecting some AC onto the DC voltage to improve low speed control. This can possibly cause irreparable damage to pretty well any sort of DC motor.

#5

Okay, motor would be sealed in as HLW does say loco is pretty much waterproof.

#6

Always good info to have and thanks for the descriptions Tony!