Motors & Drives Information

Each stage must behave as expected for the startup to be successful

COMMISSION: "TO PUT INTO ACTIVE SERVICE (usually said of a ship)." That's one dictionary definition. For rotating electrical equipment, the term often used is startup. Getting any drive up and running, however, means more than just being able to push "start" and see it come up to speed.

It's said that flying a plane is no big deal; it's the takeoffs and landings that cause trouble. With land-based, stationary machines, an analogous concern is making sure the equipment starts and stops successfully over a reasonably long period, as well as continuing to run under whatever operating conditions may exist during that period.

So . . . what is needed to successfully commission a new three-phase electric motor? Foremost is the recognition that drive performance is what the pump industry terms a wire-to-water issue. From the upstream electrical supply system to the output of the driven process, each intermediate stage must behave as expected for the startup to be successful. In theory, whoever furnishes and installs the motor itself isn't responsible for anything either upstream or down.

When is it 'the motor's fault"?

Nevertheless, as any experienced service technician knows, when a motor-driven system malfunctions, it's commonly seen as "the motor's fault" until proven otherwise. That, plus the trend towards "turnkey" jobs, means that the motor supplier/installer's best defense is to possess-and use-at least some basic knowledge of how the rest of the system should work. Equally important, of course, is an even more complete awareness of safety regulations and safe work practices.

To put any new motor in service, then, here's what to consider:

* The motor itself.

* The electrical system.

* The connecting circuit.

* The motor controls.

* The motor mounting.

* The coupling between motor and load.

* The driven machine.

Obviously, some overlap will exist among these items.

Know your motor

Start with the motor. Why? Because you will need the motor nameplate information, the motor enclosure identity, and the motor instruction sheet or manual to begin evaluating several of the other conditions on the above list. Some of what comes next here will seem too obvious to include in any list of do's and don't's. Yet failures continue to occur because just such simple matters have been neglected.

# posted by Medical Information : 4:14 AM