stepper motor need help...!!!

hi can any one plzz tell me how can i drive a stepper motor at high speed
with high torque....???

I have a 6 wire 2.5A stepper motor, when i rotate my motor at 150 to 200 RPM it draws only 0.5 - 0.6 Amperes hence it has lesser torque

What i need is that i can rotate it at even higher speed but it should draw the rated current and produce rated torque

plzzz help me...

If you think the two mid wires as one, and then you have four, then:

* Low maximum speed and torque when only one wire is active.

* When two wires is active, then you get more torque and you can get a higher rpm.

* When three wires is active, then it probably would draw more current. Probably same torque as when one wire active. But when rpm increases, the inductor inside would make the current decrease.

So - baseline is: Make a driver circuit/program that can shift to three active wires when rpm reaches a given threshold.

Another thing. If you have a torque sensor then you should be able to run the stepper with minimum power required. That is have only one wire active when torque is low and slow rpm.

With avtive wire I mean having the physical wire from the stepper connected to an open collector for example. And the two middle wires connected to voltage source.

Another thing you can do is to simply increase the voltage when the rpm increases. Remember that a stepper motor consist of inductors. More rpm will lead to increased inductive reactance, and less actual power.

i can not understand what are you trying to say in the following lines

* Low maximum speed and torque when only one wire is active.

* When two wires is active, then you get more torque and you can get a higher rpm.

* When three wires is active, then it probably would draw more current. Probably same torque as when one wire active. But when rpm increases, the inductor inside would make the current decrease.

So - baseline is: Make a driver circuit/program that can shift to three active wires when rpm reaches a given threshold.

Click to expand...

you say we have 4 wires if we consider both common wires as one. it means that we now have 4 active wires. is it right..??
if yes then we have to manipulate all four wires one by one in order to rotate the motor
so how can i shift to three "ACTIVE WIRES" when my motor reaches a certain RPM..?? and what are those 3 active wires..??


by the way
thanx for your keen interest

My bad english. Sorry.

Active wire = it simply goes current through it. Not native english.

You have a picture of your motor? Then i might explain better.

When you start talking about sqeezing performance out of stepper motor, it might get complicated.

These are some of ideas:

First is selection of the motor, you would want as low voltage motor as possible, so you could apply much higher voltage and limit current of the coil. That way current in coil reaches maximum level faster allowing maximum torque.

You should operate motor in bipolar mode (using only 4 wires)

Generate sinewave current waveform with PWM

Use rotor position device like hall sensor or encoder to maximize torque and prevent position error due to missed steps. Essentially you would use this as servo motor and do electronic commutation.