Max Current Not Being Reached Using PWM Controller

[BobsBurgers12]

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

 

[Nigel Goodwin]

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.

 

[gophert]

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.

 

[JimB]

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

 

[gophert]

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.

 

[alec_t]

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.

 

[BobsBurgers12]

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.

 

[Nigel Goodwin]

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.

 

[MaxHeadRoom78]

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.

 

[Nigel Goodwin]

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.

That's what 'soft start' is all about

 

[MaxHeadRoom78]

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!
Max,