Dear Mr. Chafekar,

The motor nameplate rating is the power output at motor shaft. Hence, motor efficiency is not part of the drive efficiency. However, if you want to know, power input to the motor terminal then motor electrical cum mechanical efficiency will come into picture.

It is difficult to indicate the drive efficiency values in this forum, because it will have many subjective statements and conditions. However, if you inform your email, it can be informed to you. It is one page table and one page statements.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Dear Mr Chafekar

I see you did not get a strong answer to your question.

What you do is calculate the absorbed power of the conveyor using ISO 5048 in the normal way.

divide the absorbed power by .97 if you have a fluid coupling

divide again by .98 for 2 stage gearbox or .97 for 3 stage gearbox to suit the number of stages (i.e. 1% loss per stage).

Select the next motor size up, making sure yoy have about 10% excess power. If you have a multiple drive it is not easy in practice to share the power, so allow a further 10%

Good luck

Graham Spriggs

LSL Tekpro ■

Dear Mr. Chafekar,

it is not just so easy to divide by 0.97 for a fluid coupling. This gravely depends on the actual coupling size in combination with effective power. Also there is an influence of manufacturer of fluid coupling.

The slip of a coupling could vary from 2 to 6 %.

If you could e-mail detailed project data I will let you know more acurate data.

For gear box I agree to approx. 1% loss per stage assuming good conditions (clean oil, ambient temperature not too low...).

For installed power you also have to take into account possible overload conditions. Then a 10 to 20 % increase is correct. ■

I note that Mr. Spriggs' reply and Mr. Obser's differ only by the efficiency attributed to the fluid coupling. I agree with Mr. Spriggs. While acknowledging Mr. Obser's point that slip at the fluid coupling can vary from 2 to 6%, if you are giving up much more than 3% to coninuous coupling slip then you should probably choose another soft start or load sharing method.

Joseph A. Dos Santos ■