FD FANS

[Venkat162]

Hi all,
I am currently working with a FD Fan for Co-Incinerator application. Kindly provide your views on the possibility of reverse rotation of such fans and how to prevent the reverse rotation? Further, would like to know what happens if the FD fan rotates in reverse direction for the subject application. Thanks in advance.

 

[Tmoose]

When a direct drive device with large diameter is rotating free-wheeling backwards and is started, the motor applies immense torque to the shaft of the driven equipment. Belt driven stuff slips the belts like crazy. Some motors are not powerful enough to start a big fan "across the lines." without benefit of a slip coupling or a soft starter or VFD.

Some pumps have anti-rotation clutches to prevent just such problems.

 

[chicopee]

Get competent electricians that know the proper connections between feed lines and three phase motors. Improperly connected, fan motors will rotate in reverse.

 

[ScottyUK]

Chicopee - that's a typical mechanical thought process: how to blame the electricians for mechanical shortcomings.

Venkat162,

Have a look at cam clutches and sprag clutches to stop the fan rotating in reverse, or if you can't get a reliable one, then a DC injection brake might be an option. If the fan already has a VFD for process reasons then it should be able to either catch the windmilling fan during start or actively hold it at zero speed.