I use a contactor to switch off the brake off an 3x380V electrical hoist.
Becouse there are only 3 phases and no control signals, I use two phases to feed the coil (380V). When the motor turns left or right, the contactor switches. So far, no problem.
When lowering the load, the moment the power is cut, the contactor closes with a delay of a few ms. This couses the load to accelerate for a moment before the brake turns on.
Is there any simple modification or sollution for this ?
Maarten.
Just as WAG does this idea meet with the approval of your governing safety people?
"When lowering the load, the moment the power is cut, the contactor closes with a delay of a few ms." That is interesting how do you get the coil to pull in when there is no power? Latching relay would not work cause you still need a signal to force the latch.
Sounds to me like you need to install a break. That would certainly solve the dropping issue.
A second contactor whose coil is wired in parallel with the brake. When the brake coil is energized, the second contactor energizes. The circuit presently in use to cut power will have to be modified so that when the second contactor's normally closed contacts open, they interrupt power to the hoist motor. There may be some local safety regulations that apply, so you need to check into that.
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