I have a 2800 rpm 1 hp ac motor with 2 big pulleys joined together with a belt, but the speed I get from the output it's too much how do I reduce it to 50rpm

change the pulley size

Do you want to change the motors speed from 2800 to 50 rpm or the device speed it's running to 50rpm? I don't think you can slow down the motor that much. If you want to slow down what it's running, like Steve said smaller pulley on the motor and larger pulley on the device.

BTW welcome aboard, did you read the thread you are asking about, it pretty much explains all the ways to reduce the motor and driven speed.

Your only other option is vfd control unit.

Expensive to upwards of $300 dollars, but available on amazon.

You have a VFD that works on a single phase motor? even if you did there would not be any torque to speak of at 50 rpm

There are also gear down systems to reduce speed. (search speed reducer and gear reduction) I have one in the shop that came from a motorized roll up door opener.  Note that there is a loss in efficiency(power) using one.

2800 rpm seems odd to me; was this a specialty motor or are you in a country that uses 50 hz?

I would like to create an account.