We usually use induction motors to turn electrical energy to mechanical, however synchronous motors are the machines on the other side of the grid (generation).

A week ago we had a student visit to the hydroelectric and ... centrals and afterward we paid a visit to a steel company. I noticed that they use the combination of the synchronous and induction motors to do the exact same job, so the output power of the motors were exactly the same so the task and the hours of operation.

Why just not using induction motors ?


As the name suggests, induction motors are inductive, it means they require inductive power input, or reactive power.

The problem with reactive power consumption is, if you max the monthly limitation out, the providers are going to charge you a lot. Why? then this is another question. Hint: Think about the phase relationship in AC circuits.

The synchronous motors can receive active power from the grid, and at the same time (under some circumstances) generate reactive power and inject it into the grid.

Usually, by this method engineers can compensate for almost all reactive power that those induction motors consume so, the units don’t have to pay any fine to the provider, and providers will be happy.

  • $\begingroup$ Sam, great points you make here- just to be clear, then, using a combination of these motor types can correct the load phase angle in the plant to minimize the reactive component, similar to the practice of adding capacitor banks or inductors to perform the same sort of task? This sounds very clever! -NN $\endgroup$ Nov 19 '19 at 8:13
  • $\begingroup$ @nielsnielsen Yes, that's is exactly what I mean. Synchronous machines do the mechanical job while delivering reactive power to the grid. $\endgroup$ Nov 19 '19 at 8:30
  • $\begingroup$ yes yes!!! -NN. $\endgroup$ Nov 19 '19 at 19:22

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