brushless vs brushed motor

[Electro nS]

i donot know if this is the right place to ask this question or i should move it somewhere else:

which is better for high inertia servo position control : brushed or brushless motor (sensored or sensorless)

i donot care about service life ( 100-150 hour max) and heating is not a problem ( not continuous duty)

i care about achieving precision for large loads and holding torque and starting torque , speed regulation , response time .....

 

[schmitt trigger]

By brushed, I assume that you are talking about a "standard" DC motor, and by brushless, you are talking about BLDC motor?

The answer to your requirements: neither one. You should be using a stepper motor.

 

[FvM]

Servo drive involves a closed loop position control, independent of motor type. Achievable precision is primarly a feature of the position sensor and feedback system.

If long motor lifetime isn't an objective, brushed DC is the easiest way to achieve high torque and dynamic.

 

[Electro nS]

By brushed, I assume that you are talking about a "standard" DC motor, and by brushless, you are talking about BLDC motor?

The answer to your requirements: neither one. You should be using a stepper motor.

ok , can u explain a little more why ??

 

[schmitt trigger]

ok , can u explain a little more why ??

The answer is complex, butI'm going to explain the basics only. I'm sure that other poster will want to add further detail
It has to do with the rotor/stator design.

First: True "stepper motors" have castelated (toothed) poles, which will self align to minimize reluctance. Castellation does create significant ripple torque, which is why most other motors use smooth poles.

Second: Holding. BLDC and brushed can be made to hold, by shorting the windings, but steppers tend to hold better in a fixed, low reluctance position.

Third: Available hardware. Stepper motor are so ubiquitous for precise position and motion, that there is lots and lots of ready-to-use hardware. There are literally dozens of driver ICs, that will do all the hard work for you. There are complete plug-and-play boards available online very cheaply.


Now...something that steppers don't do very well is high speed rotation. In that instance you may want to use something else.

 

[Electro nS]

.

Third: Available hardware. Stepper motor are so ubiquitous for precise position and motion, that there is lots and lots of ready-to-use hardware. There are literally dozens of driver ICs, that will do all the hard work for you. There are complete plug-and-play boards available online very cheaply.
else.

if i choose to design my own controller and use a pre-driver with integrated microstepping (which does all the hardwork for me ) .
Now for the motor , I choose nema 51 ,130X130mm . but what really dazzels me is the rating of these motors, please check the attachment :

these motor have different torque but same current rating ( I thought current controls torque) !! how am i going to get this toruqe, from more voltage ?? and why there is no voltage rating (except insulation is 500vAC) . how can i get the most out of the motor . I donot want to get a 50Nm motor but get 10nm because of current limitaion in controller ?! I am lost please guide me

 

[schmitt trigger]

Indeed, current is one of the variables that controls torque, but not the only one.
The actual pole reluctance (which is dependent of actual pole and rotor design) is another.

The table shows the actual rated torque the motor will produce at its rated current.
If you know your actual mechanical requirements, choose a motor which satisfies those requirements.

 

[Electro nS]

Indeed, current is one of the variables that controls torque, but not the only one.
The actual pole reluctance (which is dependent of actual pole and rotor design) is another.

The table shows the actual rated torque the motor will produce at its rated current.
If you know your actual mechanical requirements, choose a motor which satisfies those requirements.

SO for the same current and voltage (power), each motor is producing a different torque amount (depending on internal structure), and what regarding the voltage , is 24v enough for all these motors , is it enough to provide fast energizing of the coils for micro-stepping and getting the rated torque ? is there any formula that tells u how much voltage is enough for a stepper driver ??