Pulse voltage on motor

[windtakers]

I am working on a test program to see if you can use a square waveform graph as the signal on a motor(window motor). I am using a victor as the motor controller, and if the goes well i will move on to other motors, and motor controllers. My hopes are that the motor will run at half speed, but still have full torque. If you have any input or experience to this kind of experiment I would love to hear what you have to say. If u would like to see the code just ask.

Graph specs
-Duty cycle 50
-frequency 5
-amplitude 1
-off set 1( so the graph doesn't go from 1 to -1)

[Jim Wilks]

For a DC motor torque is directly proportional to current (T=kI). Since you are only permitting current for 50% of the time, you will yield 100% torque for 50% of the time. The result is 50% average torque.

[EricVanWyk]

Be careful about how you set up your experiment - there are a lot of other variables in the equation that can throw you off track.

For example, if you test torque while the motor is stalled "cogging (http://en.wikipedia.org/wiki/Cogging_torque)" will dominate. Different runs of the experiment may have the motor stalled in different positions, which will affect how much torque the motor can produce.



I would be interested to see what effect frequency has on your measurements.

[windtakers]

For a DC motor torque is directly proportional to current (T=kI). Since you are only permitting current for 50% of the time, you will yield 100% torque for 50% of the time. The result is 50% average torque.

Is there a way to control speed, and still yield max torque?

[Alan Anderson]

Is there a way to control speed, and still yield max torque?

Yes. Use gears.

I'm confused about what exactly you're proposing to do. The Victor speed controller already gives a variable duty cycle pulse of voltage to the motor. How does your scheme do it differently?

[windtakers]

Yes. Use gears.

I'm confused about what exactly you're proposing to do. The Victor speed controller already gives a variable duty cycle pulse of voltage to the motor. How does your scheme do it differently?

i didn't know the victor could do that, but what i was trying to do was find a different way of controlling the speed of a motor, and still save torque. Without have to attach different gears.

[PAR_WIG1350]

i didn't know the victor could do that, but what i was trying to do was find a different way of controlling the speed of a motor, and still save torque. Without have to attach different gears.

For a brushed motor, this isn't really possible, but there are other types of motors. I believe steppers can do that, but they have not been competition legal so far.

[Ether]

i didn't know the victor could do that, but what i was trying to do was find a different way of controlling the speed of a motor, and still save torque. Without have to attach different gears.

Use a closed-loop speed control algorithm. Then the voltage (current) delivered to the motor will be whatever is required to achieve the commanded speed.

So for example, when the load on the motor is light, only a small current will be delivered to the motor. When the load increases, the controller will automatically increase the current to maintain the commanded speed.

[windtakers]

does anyone know were i can find an example of a closed-loop speed control algorithm for labview.

[Ether]

does anyone know were i can find an example of a closed-loop speed control algorithm for labview.

Here (http://www.chiefdelphi.com/forums/attachment.php?attachmentid=10797&stc=1&d=1309478962).