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Max Current Not Being Reached Using PWM Controller

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BobsBurgers12

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I have a simple setup of a 12/24V brushed motor (max 120W) being powered through a 12/24V PWM Controller (max 200W) using a 10k Pot. The power supply is a 24V 6A brick.
For some reason I don't understand, the current (measured from the PWM controller to the motor) never goes above 2A, regardless of what I do with the pot. I have verified that the pot is, in fact, 10k ohm. For a test, I stepped down to a 12V 10A wall brick power supply to test and that also maxes out around 2A. I tried getting a different and more expensive PWM controller for testing and the max current draw seems to be only slightly higher.
By my understanding, I should be able to get the full 120W to the motor (and then some). What am I missing?
The wire gauge from the PWM to the motor looks to be at least 16ga, possibly 14ga. Wire from power supply to PWM is 20ga.

Thanks
 
The power the motor takes depends on it's load - if the load only requires the motor to draw 2A then that's all it will take.

What load do you have on the motor?, and what isn't working? - the current is irrelevant.
 
Clamp the motor shaft in a vice and then turn it on and measure the current. That is called the stall current. If it really is a 24v, 120w motor, I think you'll see more than two amps.
 
Clamp the motor shaft in a vice and then turn it on and measure the current.
Also ensure that the body of the motor is clamped solid,
otherwise you will see something far more entertaining than 2 amps on the meter!

JimB
 
Also ensure that the body of the motor is clamped solid,
otherwise you will see something far more entertaining than 2 amps on the meter!

JimB

I assumed it was attached to something, but, you're right. After he would do that, Newton wouldn't have to explain anything to him.
 
The start-up/stall current of a motor is several times the normal full-speed running current. It may be that your power supply (144W) struggles at motor start-up and goes into self-protection mode, limiting the output current to a safe level.
 
The power the motor takes depends on it's load - if the load only requires the motor to draw 2A then that's all it will take.

What load do you have on the motor?, and what isn't working? - the current is irrelevant.
That makes perfect sense. The current draw is dependent on the load. For testing, I had it attached to a small belt-driven fan. I can't imagine that it was much load. I'll try increasing the fan size to see what happens to the current.

Thanks for the explanation.
 
That makes perfect sense. The current draw is dependent on the load. For testing, I had it attached to a small belt-driven fan. I can't imagine that it was much load.

It wouldn't be much of a load. The motor will take a certain amount of power with no load at all, but above that the power consumption will increase as the load increases. Obviously a BIG fan will take more power than a small fan, as will driving the fan faster - I've just checked my 8 inch desk fan, and it's rated at 28W maximum.
 
If using PWM, you should not see the high current inrush seen with a direct supply.
I did an empirical test on a 2hp 90v DC motor and bringing the rpm up slowly with no load drew 2amp throughout the range from 0-3000 rpm.
Max.
 
And what is seen built in, in the typical T.M. controller, you don't want the belt to go from 0 to 60 in 1 second! :eek:
Max,
 
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