Torque and speed estimation for line-start IM using dot-cross Products of current and voltage vectors

The IM has been adopted widely as the driving sources of the industrial machine and the plants. That reason is that IM is robust and easy to drive. A typical line-start drive system is a motor operated valve arranged to the power plants, the chemical plants. These valves are used for application that energy supply is shut down in an emergency. So, the IM which makes valve operate is connected to 3-phase power supply directly and used. Because of this, the drive system heart of an IM has very high reliability. However, mechanical deterioration is problem. Routine inspections are carried out to those valves and reliability is secured.