SCR Four Quadrant Regenerative Drive provides smooth motoring and braking torque for brush-type DC motors. It controls motors from 1/20 through 1 HP for single or bi-directional variable speed, without using mechanical contactors. It can be operate in all 4 quadrants of power. It has two complete sets of power bridges or twelve controlled switching devices.
Selective catalytic reduction units introduced ammonia into boiler flue gas and pass it through a catalyst bed, where the ammonia and nitrogen oxide gas (NOx) react to form nitrogen and water vapor. These are used to reduce automobile emissions. These are used in chemical plants and utility power plants. It utilizes post-combustion technology and is used in coal burning and petrochemical processing applications to reduce NOx emissions.