Though the king and queen were well loved by their people, they could not fight the sands of time.
As time progressed, the King and Queen of motor control got a little older and a little less popular…
While the newer and more advanced couple, variable frequency drives and induction motors, continued to drop their cost and their popularity began to grow.
Most people don’t really consider larger motor applications even being DC anymore, but this is where the old king and queen still have a place in the fractional/sub-fractional world and in existing DC brush/brushless applications.
In the early 90’s I witnessed this change in the conveyor industry. In just a couple of years the trend went from DC to AC almost overnight. One day our systems had 1/3-1 HP DC motor and DC speed controllers and then it was AC motors/gearboxes and variable frequency drives. This transition made us need to learn these new systems quickly.
In the beginning, the advantage wasn’t so obvious; but as time went on and the technology kept improving the “take-over” took place. The VFD & AC motor became more cost effective and the DC Speed Controller and Motor became more expensive and by then we forgot all about DC systems.