power supply problem

[rashdan]

Hi all,
I've built 3 axis stepper motor driver. This is I've built Tach42 3 axis board. And i changing irfz44n to irf3205. I have 24v 720 watt transformer and 3.7amp 2.5v stepper motor.
when i connect the transformer with driver and stepper the motor heats up.
i don't now what is the problem. what can i do for resolve this problem.
thanks.

[doorknob]

Did you build the "3 axis stepper driver board" shown at the top of this page?

Tach42 3 axis board

If so, did you also build the 3-axis chopper board circuit shown at the bottom of that page?

If you did not build the chopper circuit, and you are using a higher voltage power supply than the motors' rated voltage, then it appears that you will need to add a "high wattage power resistor (sometimes referred as a ballast resistor)" to the circuit shown at the top of the page for each motor.

[rashdan]

No i did not build 3-axis chopper board circuit. Is this important?
And is this work with 31.25 amp?

[doorknob]

I do not have direct experience with this driver circuit, but my understanding of its operation from reading the schematic is that the basic circuit is a very simple one, and so if you are going to use a higher voltage than the motor's voltage rating, then you will have to add a series power resistor to drop the voltage to the motor, otherwise you will be applying too much voltage to the motor, which will draw too much current through the motor.

My understanding of the chopper circuit at the bottom of that page is that you can add it to the circuit shown at the top of the page - that will let you use a higher voltage than the motor's rated voltage, and the chopper circuit will be responsible for limiting the motor current. That may allow you to run the motors at a higher maximum speed.

I did not find a written description of the circuit operation on that web page, but you might want to do a search to see if you can find one that explains the circuit operation and the need for a series current-limiting resistor if you do not use the chopper circuit.

>>And is this work with 31.25 amp?

I do not understand that question, sorry.

[KOC62]

The document states that the 3-axis FET unipolar driver uses 50A FETs but has only heatsinking to handle 50watts. As doorknob explaned you need power resistors to limit your motor current to their designed values. The documentation tells you how to calculate the resistance value for your motors.

If you want a more efficient driver then you can build the additional chopper circuit. This will eliminate the power resistors. It's your choice.

Any design changes you make may make the circuit unstable. You would be better to talk to the designer of this board if you change the output FETs for higher power units. There could be a larger FET input capacitance that you may have overlooked, and which could affect the drive circuitry. There could be PCB tracks that are too small for the additional current and who know what other "gotchas".

A 31amp power supply is a whopper. I'm not sure that your motors are that big, are they? This may assume that all motors are on at full power for several minutes? For more information read this.. Support

Also note that this stepper driver is very simple and does not do micro-stepping to provide smooth low motor RPM. Secondly, it has no protection against a stepper motor's resonance where the torque becomes too low to spin the motor. Hence the motor stalls at a certain RPM - and is motor dependent, so I can't tell what that RPM is. Quality does have a price.

[rashdan]

hi
My stepper motor 3.7Amp 2.5Volt.

[KOC62]

That's fine.