About DCMotors

[heavenly]

Hi,
Most of DC Motors ,starts from speed from 1000pm onwards..
why cant we get 100rpm with 10Nm Torque capacity motors
any problem making such motors without gear head


Thanks in befor

John

 

[drawoh]

heavenly,

Look for direct drive rotary motors. The following website is the first thing I thought of. A Google search will produce many more.

http://www.danahermotion.com

A low speed, high torque motor is going to be large, possibly larger than a conventional motor and gearhead. They tend to be expensive too, possibly more so again than a conventional motor and gearhead.

All of this depends massively on your requirements.

JHG

 

[heavenly]

Hi Drawoh.,
Thanks for ur message,well why cant we make small
size motor....with high capacity..for ex 100rpm with 20Nm torque capacity..sizes dia50 x 80mm length..?


Thanks in before


john

 

[drawoh]

heavenly,

I am a mechanical guy who looks in catalogues for motors that meet requirements. The actual motor design is not my department.

On a permanent magnet DC motor, the torque controls the motor current, and the stress on the shaft and motor housing. All this affects the wiring and the size of the mechanical hardware. Any high torque motor is going to be big.

Consider also that your maximum power occurs at half of your no-load speed, and your maximum efficiency occurs at quite a bit more than half of no-load speed. You are looking for a motor with a no-load speed of 150rpm, and 100Nm torque at 100rpm, unless you do not mind wasting power and dumping heat.

If you are looking for a constant speed drive, look into speed reduction from a gearhead, chains, timing belts or V belts. It will be way cheaper.

JHG

 

[sreid]

Torque production in a motor is limited by temperature rise and magnetic and electrical loading. T. J. E. Miller give number ranges for Torque per Unit Rotor Volume (TRV) for aerospace motors (continous torque)as

45 to 75 kN-m/m^3

Liquid cooling can raise this to

130 to 220 kN-m/m^3

 

[sreid]

A second thought; you might take a look at high pole count reluctance motors. They are basically variable reluctance (VR) stepper motors but they can be controlled using sine current drive. High torque at low RPM can be acheived. VR torquers are used as direct drive motors in robots.

 

[sreid]

A third thought-Ultrasonic piezoelectric wave motors.

https://dspace.mit.edu/handle/1721.1/16875