What is phase reversal?

Electrical phase sequence can sometimes be incorrect (out of phase), causing an induction motor to run in the opposite direction from which the operator expects. This happens when the equipment is initially installed. It is possible to run into a situation where the electrical legs are out of phase with one another. With most electrical chain hoist, reversing the electrical phase will make the electrical motor run in opposite direction of what your controller is asking it to do. In other words, up is now down and down is now up.

Why do I care about phase reversal?

When phases are reversed, the upper and lower limits of the hoist will no longer work. Because the motor thinks it is going up when it is going down, it is no longer being signaled to stop at the upper and lower limit location that have been set. This can lead to a dangerous situation where the hook block is pulled up against the hoist body with the full force of the motor (sometimes called two-blocking). Because these limit switches protect operators from this, it is important to make sure the phases are properly sequenced at install.

My hoist is reverse-phased. Now what?

Electrical phases need to line up accordingly to how the windings of the motor are built, so that it can function in a clockwise or counterclockwise manner. If you find your hoist is reverse phased, switch your L1 and L2 wire placements in order to correct the problem.

Share This