### Author Topic: Selecting the Right Motor Driver/Speed Controller  (Read 1725 times)

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#### Builder1

• Jr. Member
• Posts: 46
##### Selecting the Right Motor Driver/Speed Controller
« on: January 27, 2009, 08:33:41 PM »
Hello All,
Up until now I've been doing mostly other things which are not related to electronics like planning my course of action and building the body of my robot. Now that I'm done with all the non-electronic tasks, I will need your help in choosing the right electronic components. Suppose I have a DC motor with the following specs.

Voltage: DC24V
Rated speed: 2600R/MIN
Rated current: 28A
Output:50W

How do I Know how to pick the appropriate motor driver for this particular motor? Is 28A the peak amperage and 50W the peak output of this motor? I would like to know 'cause I don't want to burn up my motor driver just to find out what it can or can not handle. Thanks in advance.
« Last Edit: January 27, 2009, 09:22:36 PM by Builder1 »

#### ArcMan

• Supreme Robot
• Posts: 519
• Mmmm... Plasma
##### Re: Selecting the Right Motor Driver/Speed Controller
« Reply #1 on: January 27, 2009, 09:00:27 PM »
Hello All,
Suppose I have a DC motor with the following specs.

Voltage: DC24V
Rated speed: 2600/MIN
Rated current: 28A
Output:50W

How do I Know how to pick the appropriate motor driver for this particular motor? Is 28A the peak amperage and 50W the peak output of this motor? I would like to know 'cause I don't want to burn up my motor driver just to find out what it can or can not handle. Thanks in advance.

Somethin' ain't right with those numbers.
DC motor output power = V * I * Efficiency.  V * I is 672 Watts (almost 1 hp).  Unless your motor's efficiency is 7.4% (which it's not), that current must be 2.8A, not 28A.  Maybe it's a label misprint.  How big is the motor?  Give us a picture with something in it that shows scale and we'll be ablle to tell you whether it's a 28A motor or a 2.8A motor.

#### Builder1

• Jr. Member
• Posts: 46
##### Re: Selecting the Right Motor Driver/Speed Controller
« Reply #2 on: January 27, 2009, 09:21:37 PM »
Hi ArcMan,

Thanks for responding, here is the pic of the motor.
« Last Edit: January 27, 2009, 09:24:50 PM by Builder1 »

#### ArcMan

• Supreme Robot
• Posts: 519
• Mmmm... Plasma
##### Re: Selecting the Right Motor Driver/Speed Controller
« Reply #3 on: January 27, 2009, 10:01:52 PM »
Ah.  That explains it.  The motor is 500W, not 50W as stated in your OP.
I would say that the 28A is the rated full load current.  So you will need a drive capable of driving 28A @ 24VDC.
Most of the inexpensive drives for our hobby only go up to 25A.  You'll need to step up to something bigger, like a couple of the drives on this page:
http://www.robotmarketplace.com/products/speed_controllers_main.html

There are probably cheaper commercial drive options that will work for your motor.  I just don't know of any.
« Last Edit: January 27, 2009, 10:14:54 PM by ArcMan »

• Supreme Robot
• Posts: 11,658
##### Re: Selecting the Right Motor Driver/Speed Controller
« Reply #4 on: February 07, 2009, 07:25:28 AM »
Quote
I would say that the 28A is the rated full load current.  So you will need a drive capable of driving 28A @ 24VDC.
Not really sure about that . . . 28A at 24V is 672W . . . perhaps that's output power, after subtracting efficiency?

Some motors are rated by no-load, while others are rated at stall. 90% of the time they are rated at no-load. You can't really know without using the motor or seeing torque/current curves in a datasheet.

It appears to come from China, and no datasheet available, at least with google . . .