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Motor selection suggestions needs.

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Member level 4
Feb 24, 2002
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In a project I need two motors to drive an object. The motors always have same directions and speed. The object's weight is below 100-kg. Control system and motors should be cheap.

My problem is which kind of motor should I use: dc, ac or step motors. If I choice dc or ac motors it needs a lot of electronics and software developing. If I choice step motors it is easier to make software and not much electronic, but step motors costs more.

Could you experts please give me some advices? Thanks in advance!

Best Regards,

regular motors

It all depends upon the need or not to precisely control the position. If there is a need and you use a regualr AC or DC motor, you will need some form of measuring device and a feedback loop which will make the total cost more in line with the stepping motor and give you some design headaches involving a nonlinear feedback system.

If you do use a regualr motor, the DC type will usually have a higher starting torque and more precise control of speed by pulse width modulating the power.

First of all you must determine the power needed ( speed of motion of you charge ) and the precision needed. Step motor are more easy if you need precice movment, but are not very efficient in term of power and subjet to resonnance.
So if you need a quite fast movment, look at DC motors, otherwise step motors are good.
In both cases the drivers are very important.
I use allegro ICs.

Well talking about carry a 100kg load then DC geared motor will be a good choice, you can add encoder if you need precision movement. Although stepper motor is easy to control but the power and motor size will be large and expensive.

100kg mass ok but what is the speed ? Speed importand parameter.

For example you cant use step motor for higher speed. (Not practice)

Do you use position, torque and/or speed control ?

DC Brush motor
Simple motor driver. High speed, high torque, simple speed control, cheap.

Disadvantages : finite Brush life,
precision position controls applications needs complex controller.

Brushless motor
High speed, high torque, precision speed control
Disadvantages : Cost, complex control, complex motor driver.

Step motor
Simple motor driver for low speed applications.
Simple precision position control
Disadvantage : low torque and speed (usualy), expensive for high power.
high speed applications not practice.

Induction motor
Advantages: Simple construction, cheap

Disadvantages : speed and position control need complex controller and driver. precision position control not possible.


Thanks very much for your suggestions.
Here are the parametras:
load = 90Kg,
speed = 0.25m/s
Power supply = 24V AC
efficiency = 60%

After calculation I got around 7.0A of current for each motor. It is a huge of current for one motor. Is this possible?

Best Regards

Ok but we must know another parameters.

What is the accerelation and deccerelation time ?
Friction ? Inertia ? Travel direction vertical or horizontal ?

This is a physisc problem.

I add good pdf for motors and motor selection.

You can find here a flowchart to help you to choose the right motor.
There is also a lot of explanation about motor theory (stepper, dc, brushless)

**broken link removed**

Look at this page for motor needs calculation :

only for DC and.. in french.. :oops: sorry

:roll: :roll:

I think that the motortec doc I mentioned is in fact the original pdf of the
docs posted by Bunalmis :eek:

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