Motor curent distribuition
Posted by Grumpy Mike
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Motor curent distribuition August 23, 2011 11:14AM |
Registered: 14 years ago Posts: 24 |
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Re: Motor curent distribuition August 23, 2011 11:22AM |
Admin Registered: 17 years ago Posts: 7,879 |
Yes it is plenty as it is 96W. My machines take about 60W ignoring the heated bed. The motors take less current from the supply rail than the set coil current.
[www.hydraraptor.blogspot.com]
[www.hydraraptor.blogspot.com]
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Re: Motor curent distribuition August 23, 2011 03:02PM |
Registered: 14 years ago Posts: 24 |
Thanks,
With 6A to divide over four motors with two coils per motor, that would see me setting all the motors to 0.75A.
However, I suspect that a bit more current in the X and Y and a bit less in the Z and extruder would make better use of the torque producing current I have.
That is I could move the X & Y faster at the expense of not moving the Z as fast as it doesn't change very often during the course of a print.
do you know how much less it takes.Quote
The motors take less current from the supply rail than the set coil current.
With 6A to divide over four motors with two coils per motor, that would see me setting all the motors to 0.75A.
However, I suspect that a bit more current in the X and Y and a bit less in the Z and extruder would make better use of the torque producing current I have.
That is I could move the X & Y faster at the expense of not moving the Z as fast as it doesn't change very often during the course of a print.
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Re: Motor curent distribuition August 23, 2011 07:06PM |
Admin Registered: 17 years ago Posts: 7,879 |
Sorry, 6A at 12V is only 72W, not 96W, I am not very well today!
If you set the current to say 1A using vref then that is the peak current with one coil on. When both coils are on it is 70% to each. Either way the power dissipation is the same. It is I^2R, so for typical motors with 1.65R coils, only ~ 1.7W. There will be some switching losses that make it a bit bigger, but you really don't need to ration current between motors with a 72W supply.
I set the current to 1A on all my axes and 1.3A on the extruder. My z-motors are wired in series. The machine only takes 60W when extruding, 20W of that will be the extruder heater. The 60W is measured at the mains and I am only using a cheap PC PSU, so the 12V power will be substantially less than that. I doubt it is even 80% efficient at such low powers, so perhaps about 4A @ 12V in total. 1.8A of that will be the extruder heater. leaving 2.2A for all the motors.
I run the heated bed from a 17V PSU and that takes about another 250W from the mains.
Edited 1 time(s). Last edit at 08/24/2011 03:37AM by nophead.
[www.hydraraptor.blogspot.com]
If you set the current to say 1A using vref then that is the peak current with one coil on. When both coils are on it is 70% to each. Either way the power dissipation is the same. It is I^2R, so for typical motors with 1.65R coils, only ~ 1.7W. There will be some switching losses that make it a bit bigger, but you really don't need to ration current between motors with a 72W supply.
I set the current to 1A on all my axes and 1.3A on the extruder. My z-motors are wired in series. The machine only takes 60W when extruding, 20W of that will be the extruder heater. The 60W is measured at the mains and I am only using a cheap PC PSU, so the 12V power will be substantially less than that. I doubt it is even 80% efficient at such low powers, so perhaps about 4A @ 12V in total. 1.8A of that will be the extruder heater. leaving 2.2A for all the motors.
I run the heated bed from a 17V PSU and that takes about another 250W from the mains.
Edited 1 time(s). Last edit at 08/24/2011 03:37AM by nophead.
[www.hydraraptor.blogspot.com]
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