High frequency drives and coreless motors?

[rrinker]

 High frequency "supersonic" or "silent running" or (pick a specific brand's name for it) PWM doesn't hurt coreless motors. It's the LOW frequency form that does, used on cheaper decoders (but you can't determine that by price alone - the NCE D13SRJ is $12ea in a 10 pack, and has high frequency PWM drive. The actually more expensive Bachmann DCC on-board decoders do not).

                       --Randy

 

[fwright]

 Only the "silent drive" decoders have high frequency output.  Be aware that the problem area is not the very lowest speed operation, but more mid-range, especially under load. 

At the very slow speeds, the pulse duration is very, very short; and there is time between pulses to cool. 

At mid-range speeds, the pulse is theoretically on 50% and off 50%.  Now there is a lot more time at full voltage and current, and a lot less time between pulses to cool.  The lower RPM at mid-speeds allows greater current during the pulse.

Many DC throttles use pulse injection - replacing pulses with DC once out of the slow speed range to avoid overheating issues with coreless motors.  But these throttles also typically use much lower base pulse frequencies than a silent drive decoder. 

At the near top speed end, PWM looks pretty close to ordinary DC.  The higher RPM of the motor limits the current during the pulse duration.

If you look at the links Rich gave you, there is obviously a mix of opinions out there.  The problem is - as you have apparently discovered - that many of the decent HOn3 remotoring options are coreless motors because of their size.  Many of LocoDoc's remotor kits contain coreless motors.  I am installing one in my FED 2-6-0.

ESU claims their silent drive decoders will work with coreless motors; that the base pulse frequency is high enough to prevent overheating of coreless motors.  I'm pretty sure many decoder manufacturers will say the same thing.  But that's theory to me, since I'm still in DC.

You might get more real world experience at the HOn3 Yahoo Group.  A fair number have been experimenting with installing sound (usually with micro-Tsunami decoders) in their HOn3 locomotives.  All the HOn3 modular groups I know of use Digitraxx or NCE DCC as their standard power.  Surely some of those brass locomotives have coreless motors installed.

A final word of caution that you probably have already thought of or are aware of - make real sure the mechanism is free running before installing a coreless motor.  Some of the HOn3 loco builders I know use a cheap can or open frame motor for testing the mechanism before they risk a $50+ coreless motor.

hope this helps

Fred W

[Hamltnblue]

 Basically coreless motors aren't used because of heat issues.  some decoders can handle them but why have to bother with matching a decoder to the motor?  It's best to just go with a caned and not worry about decoder or heat issues in the future.

[richg1998]

 Go look at the links in the below link, Try to separate fact from opinion. usually fact will be from those who successfully operate coreless motors using DCC. The link will also be a lesson how how you can find answers using Google. Just remember to separate opinion from fact.

I do not use coreless motors so I have no experiences with them.

http://tinyurl.com/2vlzz9t

Rich

[tbdanny]

Hi,

Just wondering, does the high-frequency output from DCC decoders damage coreless motors?

Thanks in advance,

tbdanny