AM2 DOL Motor

[Pete999]

Trying to get my head around something for a youngster I know about to study for AM2. Someone mentioned that one of the faults has something to do with the Motor running in the wrong direction and what is the way to reverse the rotation, I take it that the Motor is 3 phase am I correct? Not done the AM2 far to old and decrepit.

 

[ElectroChem]

If I recall, the 10% was a fudge factor for when things like motor nameplate current, power factor, overload setting and supply voltage were... less than precise.
With modern motors, you should set the overload to the FLC of the motor.

 

[Lucien Nunes]

isn't that equation missing the motor efficiency

Indeed it is. That was part of my question about the 10%. Guess the pf, ignore the efficiency, but then add 10% for luck. Seemed like a less than ideal way to teach people to do things.

 

[davesparks]

Indeed it is. That was part of my question about the 10%. Guess the pf, ignore the efficiency, but then add 10% for luck. Seemed like a less than ideal way to teach people to do things.

They get away with it as the average electrician doesn't get anywhere near a motor or setting the overloads these days.

 

[Lucien Nunes]

To be fair, the setting will come out about right, but it's hard enough getting people to correctly interpret motor input and output power ratings. Suddenly making the distinction between the two disappear must be confusing.