Dear All;

Our ID fan (110 KW) of Boiler tripped on low water level of steam drum. Again started in auto mode as per logic sequence. however it is observed that direction of rotation is reversed. (Clockwise from original anti-clockwise).

We have stopped ID fan manually & MCCB of VFD were made OFF & then ON. Again started ID fan in manual mode & found direction of rotation in correct manner i.e. anticlockwise.

We haven’t done anything in VFD setting / tampering by any means. What will be the reason for change in direction without changing phase sequence electrically as well as in VFD & any remedial suggestion to avoid such things.

 

Sounds to me like there is something that causes your fan to turn in the reverse direction after the initial trip...maybe a reverse air flow or draft. Then when the VFD starts up after the trip, the fan is already turning in the reverse direction. It will then continue to turn in that direction. However a standing start from full stop, will always start in the desired direction.

 

Hello;

But We have tried with other motor (FD Fan) we rotated it in opposite direction (manually with @ 5/7RPM) & given a start command from VFD. First It's speed became zero & it start rotating in correct direction. So this seems impossible that motor is running in reverse direction & continues in same direction (i.e. reverse) after getting start command.