Lastspikemike My only point about stall current load is that it occurs when motor torque equals load. While it is correct that you will find this number if you momentarily lock the armature that is not the definition. The number is the current draw just as the armature stalls.
My only point about stall current load is that it occurs when motor torque equals load. While it is correct that you will find this number if you momentarily lock the armature that is not the definition. The number is the current draw just as the armature stalls.
But, you still disagree with Ed and dcciwiki that it is the definition of stall current. So, how do you define stall current?
Alton Junction
Lastspikemikehe number is the current draw just as the armature stalls.
why is that current not the same a moment after it stalls, or 10 sec later? what changes?
greg - Philadelphia & Reading / Reading
In my experience, 'locked-rotor' means keeping the armature from rotating in response to magnetic torque -- it doesn't matter whether instantaneously or for some more extended period of time. There is something of a distinction without a difference in trying to make 'instantaneous' and 'locked' mean two different things in this context.
On the other hand, there may be a difference between momentarily stalling a turning motor and applying voltage to one that is not turning. In the current (no pun intended) context, we are applying external force to a turning motor that 'causes it to stop turning' and reading the current it draws at that moment. That is the point at which stall torque can be measured, or stall current measured. I would argue that it is the way it ought to be measured experimentally in the current situation, whether by bringing a locomotive to a halt or pinching the shaft of a motor.
In my opinion the IMPORTANT issue for the OP is that the amount of current that makes a decoder 'melt' is larger, perhaps wildly larger than the 'stall current' observed from stopping shaft rotation. The procedure we were recommending was that the motor stall/locked/whatever current be MEASURED as an early step in diagnostics, to confirm there isn't some issue that might cause high current -- to me, this problem sounds like there is some kind of induced short, probably through the motor somewhere, that passes enough current to roast part of the decoder but not show obvious, visible damage on some other part of the locomotive.
A surprising thing about the story 'so far' is that the OP reports no overcurrent protection 'firing' to keep the decoders from melting. This would tell me there is a high current from 'whatever is melting' but it isn't high enough to trip protection -- someone 'in the know' might advise him to install one of the fast-acting adjustable breakers in his power supply system...
Lastspikemikebemf stops and heat resistance starts.
there is always heat generated by a motor due to a current flowing thru the wires. the difference between that power when moving and stopped is that the bemf reduces the effective voltage across the windings. the current equals the applied voltage - the bemf due to the armatures turning in a magnetic field divided by the wire resistance which is a constant.
so the maximum current is when the bemf is zero
the other aspect of a turning armature is that it moves the air which helps dissapate the heat.
LastspikemikeA motor or engine stalls when the load exceeds the torque the motor or engine can exert.
on most model locomotives, the motor has more torque than traction and when the load exceeds the traction the wheels simply spin. (see my original post). the traction is typically ~25% of the weight on the drivers.
the wheels would slip if you simply blocked a model locomotive from moving. you would have to press down on the locomotive to stop the wheel from spinning and stall the motor, as you said
LastspikemikeThe OP made no mention of his locomotive stalling anyway.
the OP said his decoder melted. the decoder needs to have a sufficient current rating. stall current is typically the value the decoder should be rated at or exceed. it shouldn't "melt" if is does, even when stalled
LastspikemikeLocking the armature and applying voltage may not yield the stall current.
may not but close enough. why not make some measurements yourself
Lastspikemike The OP made no mention of his locomotive stalling anyway. I think this speculation involves the pursuit of red herrings.
The OP made no mention of his locomotive stalling anyway. I think this speculation involves the pursuit of red herrings.
elmertc19 I bought it new off E-bay a little more than a year ago and in that time, it has melted two decoders. Is there something I should check for or do to prevent this from happening again?
I bought it new off E-bay a little more than a year ago and in that time, it has melted two decoders.
Is there something I should check for or do to prevent this from happening again?
True, the OP made no mention of his locomotive stalling. What he did mention was that the loco has melted (fried) two decoders. In trying to determine if excess current is being drawn by the motor, you measure stall current. If the OP had mentioned that his loco was stalling, you woudn't measure stall current. Two different things.
If there has been a pursuit of red herrings in this thread, it has been the continuing attempt to redefine stall current.
richhotrainIf there has been a pursuit of red herrings in this thread, it has been the continuing attempt to redefine stall current.
Sometimes I wish there was a "LIKE" option to thread replies. Rich has made an excellent summary here. I like it.
Regards, Ed
gregc Lastspikemike It should be simple enough to build a decoder that won't accept more than x amps. you say it's simple. what do you think it would take?
Lastspikemike It should be simple enough to build a decoder that won't accept more than x amps.
you say it's simple. what do you think it would take?
rrebellThat one is easy, a reseting thremal breaker which do exist, but do they in the size ect. thjat we need.
Broadway Limited Paragon 3 decoders have motor protection built in, customizable using CVs, however, when they install motors that are too close to that limit it results in stuttering and shutdowns that become very annoying pretty quickly.
CV247
This value sets the length of time in seconds that a motor over current condition is allowed before removing motor power. This condition exists when the motor is supposed to be moving, but is not. A value too small may cause the over current circuit protect to falsely activate, while too long may cause damage to the motor or decoder if the motor is jammed from moving and motor power is applied. Once the circuit is activated, simple set your throttle to zero momentarily, than throttle up (assuming the problem was removed) and the motor will receive power again. If backEMF (CV10) is disabled, the over current is also disabled. Setting the value to 255 disables this function.
Good Luck, Ed
wrench567 I believe the OP has left the building.
Once again. I wonder if some of these posters get flustered at all the extraneous responses that really do not help them?
If you are still out there, please read the posts that are helpful (ie: is the decoder rated for the locomotive, is the loco running properly). Some of the folks here really want to help you.
LastspikemikeThe stuff you are all complaining about we learn at law school...
Mike, it should come as no surprise that you are not the only lawyer in this group.
I am not going to "out" any of the others. I correspond off the forums with many of the people in here, and have developed several strong friendships. The other people in here that share your profession are enjoyable, non-argumentative, and even helpful when they know the answer.
What you are, is the only person in here who behaves like you do. You argue so many sides of every topic, and you rarely have any understanding of what you are saying. You disagree with long-established truths of model trains. You ignore knowledgeable people that know the real answers. Then in the end, you just copy-and-paste something that someone else said and act as though you have some sort of deep understanding.
You especially love to do this in threads posted by new participants. This just gives them a sour experience and they do not come back. I personally know of one great person you ran off with your act. That was a tragedy.
I assume you do this to be destructive and chaotic.
How come all the other lawyers in here never say things like this? How come they can just talk about our model trains, share pictures, share experiences, and learn from one another?
What are you trying to do in here?
SPIKE went another thread.
And I know by typing this I gave you some of the attention you so desperately crave.
-Kevin
Living the dream.
Interesting, what kind of lawyers? Studyed real estate law some for writing and reading contracts and dealing with cities along with tenent landlord law, now you can proubly guess what I used to do.
looks like some decoders montor BEMF and recognize when the motor has stopped turning and may shut down or at least cycle power.
they don't explicitly monitor current like boosters, circuit breakers or auto-reversers, so are still prone to damage if the motor's normal operating current exceeds the rating of the decoder.
LastspikemikeI'd buy and install an ESU decoder. https://www.esu.eu/en/news/read-news-entry/article/lokprogrammer-5012-verfuegbar/3/
https://www.esu.eu/en/news/read-news-entry/article/lokprogrammer-5012-verfuegbar/3/
your link is not to a decoder
(1) I can't see the pictures he posted of the damaged decoder. Has anyone actually identified the section that 'melted'?
(2) If I were the one 'troubleshooting', right after I measured the stall current, I would let the motor slowly turn through a few rotations and see whether there was a bad commutator or fault in the winding insulation that was causing high current in only a particular position. It might at some point be valuable to look at the armature to see if there are any signs of shorting or burning -- this is something of additional concern if he has a coreless motor.
It is my considered opinion that Ed's advice in the first reply in this thread and in the post concerning the CV adjusting overcurrent protection have given the OP as much assistance as this thread needs, or is likely to, supply... and the OP needs to find out what is cooking decoders before putting in a different manufacturer's product.
Lastspikemike All new ESU decoders are equipped with output current overload protection, motor, lights everything.
All new ESU decoders are equipped with output current overload protection, motor, lights everything.
gmpullmanBroadway Limited Paragon 3 decoders have motor protection built in, customizable using CVs, however, when they install motors that are too close to that limit it results in stuttering and shutdowns that become very annoying pretty quickly.
ESU decoders use CV247 as one of the automatic-uncoupling functions. So we need to look elsewhere. In the latest manual I have for LokPilot v.5, the "Motor Overload Protection" is bit 5 of CV124, the "Extended Configuration #2) which means that you'd increment the value by 32 if the protection is OFF and you want it ON, or decrement the value by 32 if... well, suppose you wanted to stall-test your motor and didn't want it to automatically cut off.
This is on p.81 of the version 7 edition of the LokPilot manual from ESU (dated May 2021), available via this link.. You can select both the LokPilot and LokSound manuals from this page, and I presume as later versions become available they will become listed here.
Be advised that I had to scroll the license agreement down to the bottom for the first manual to be able to click the actual 'download' button.