braking of an ac motor


Thread Starter


the 3 phase slipring induction motor is used in a crane for hoisting a paper roll. now mechanical braking is applied by using thrustor.

i want to apply the brake without this mech brake.the motor stops suddenly if electric braking is applied, because of that the papaer roll it hoists swings.

i need the solution for smooth braking.
help me please!
Had a similar problem years ago with a 5hp 3phase manual industrial table saw. Wanted to stop the 12inch blade quickly for operator safety. Ended up apply DC thru an interlocked relay to 2 of the phase.

I do recall under estimating the amount of current required and had to increase the DC power supply and relay. Worked well, stopping the blade with in a few seconds.

But it was very hard on the relay causeing failures every two to three months. Adding snubbers across the relay contacts improved reliability greatly.