Oklahoma unlimited journeyman's

[larmee]

I recently took the OK unlimited journeyman's exam. One if the questions was on a motor and the best I can remember it asked the maximum current rating of a 6.5 amp motor with a service factor of 1.15. I know that the service factor is used to size the overloads using the nameplate amperes and the service factor is directly related to HP. What is its relationship to the maximum amperes? There were 4 answers available with only 2 logical possibilities. 6.5 and 7.5.
Thank for an explanation and correct answer

 

[bob]

Was one of the answers a 15 amp or 20 amp?

 

[larmee]

Was one of the answers a 15 amp or 20 amp?

To be honest I do not remember what all the answers were I wish that I could.

 

[larmee]

To be honest I do not remember what all the answers were I wish that I could.

15 or 20 amps doesn't seem to ring as one of the choices. Seems like all the values were 10 of less.

 

[texie]

I recently took the OK unlimited journeyman's exam. One if the questions was on a motor and the best I can remember it asked the maximum current rating of a 6.5 amp motor with a service factor of 1.15. I know that the service factor is used to size the overloads using the nameplate amperes and the service factor is directly related to HP. What is its relationship to the maximum amperes? There were 4 answers available with only 2 logical possibilities. 6.5 and 7.5.
Thank for an explanation and correct answer

7.475 amps or rounded to 7.5.

 

[larmee]

7.475 amps or rounded to 7.5.

That was my answer choice.
Thank you for your response.

 

[bob]

I misread your question. I thought you wanted the max overcurrent device.

 

[larmee]

I misread your question. I thought you wanted the max overcurrent device.

Thanks for the responses. I was curious as whether I had the correct answer.

 

[J.P.]

I remember a question that read "which is better a 12v or 24v transformer?"

I still don't get what they were after. Did you see that one?

 

[kwired]

A motor with 1.15 SF should be able to deliver 115% of its rating without damaging the motor is the basic idea of service factor.

You typically see SF or 1.0, 1.15, or 1.25, and does not matter how big or small the motor is.

Motors with SF of 1.15 or greater can have overload protection set at 125% of FLC, all other motors can have set at 115%. See 430.32(A)(1)

Most motor overload charts or dials on adjustable overloads are set to trip at 125% of the listed current in the chart/value on the dial. If you have a motor with less then 1.15 SF you usually need to select or set your device for 90% of the FLC to provide proper protection. (many forget or do not realize they need to do this with a low SF motor)