solved here!

Problem Solving

Problem Solving can require multiple skills in motor design and performance as well as a good understanding of the application of that motor.


For example:


A set of 5 synchronous motors were supplied power from one transformer in a large Municipal setting which provided a high volume of air for the end process.  These units had been installed in the 1960’s and had run successfully for many years.  One of these motors was replaced by an Induction motor to reduce the replacement equipment cost.  The induction motor rating was increased 20% above the synchronous motor ratings.


A second synchronous motor was overhauled with the idea that the induction motor would provide the base capability with the synchronous machine providing whatever additional air flow was necessary.  While the induction motor was installed, the synchronous motor provided the necessary process air.


All was working well until the induction motor was in operation.  Then difficulties were found in synchronizing the synchronous motor.


During the investigation of the problem, the induction motor which together with its blower put a high noise level into the machinery room, was shut down to permit communication.  When the induction motor was shut down, the synchronous machine worked very well.


The findings were that the induction motor produced a higher voltage drop at the transformer secondary and the synchronous motor could then not accelerate high enough in speed to synchronize.  In the prior configuration, after the first synchronous motor had been started, that first unit would supply the reactive current required to start the next unit, and so on.


It’s not clear at this time how this will be resolved although some suggestions have been made.  Using one of the idle synchronous motors as a condenser, when the induction motor is running, is probably the best arrangement.