# Thread: MI PSI Practice Exam Question

1. Junior Member
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Jun 2015
Location
Muskegon, Mi, USA
Posts
16

## MI PSI Practice Exam Question

Hey everyone,

My apprentice is about to take his Journeyman's test this Thursday through PSI. He got a question wrong on his PSI Practice Test and asked me for input. I'm embarrassed to say I couldn't see how they came up with their answer.

Q: What is the motor nameplate FLA rating for a 5 HP single-phase motor, 230 volt with an efficiency rating of 95% and a power factor of 90%?

A: 8 amps
B: 16amps
C: 19amps
D: 25amps

My apprentice chose the answer D, but the correct answer is C according to the practice test. Can anyone explain the formulas needed to come up with the answer? Any help would be appreciated!

2. Originally Posted by Padilla616
Hey everyone,

My apprentice is about to take his Journeyman's test this Thursday through PSI. He got a question wrong on his PSI Practice Test and asked me for input. I'm embarrassed to say I couldn't see how they came up with their answer.

Q: What is the motor nameplate FLA rating for a 5 HP single-phase motor, 230 volt with an efficiency rating of 95% and a power factor of 90%?

A: 8 amps
B: 16amps
C: 19amps
D: 25amps

My apprentice chose the answer D, but the correct answer is C according to the practice test. Can anyone explain the formulas needed to come up with the answer? Any help would be appreciated!
5 HP is 3.73 kW or 3730W. The factor is 0.746.
Divide that by the pf and efficiency and you get 4363 VA
Divide that by 230 V to get Amps.
So call it 19A.

3. Originally Posted by Padilla616
Hey everyone,

My apprentice is about to take his Journeyman's test this Thursday through PSI. He got a question wrong on his PSI Practice Test and asked me for input. I'm embarrassed to say I couldn't see how they came up with their answer.

Q: What is the motor nameplate FLA rating for a 5 HP single-phase motor, 230 volt with an efficiency rating of 95% and a power factor of 90%?

A: 8 amps
B: 16amps
C: 19amps
D: 25amps

My apprentice chose the answer D, but the correct answer is C according to the practice test. Can anyone explain the formulas needed to come up with the answer? Any help would be appreciated!
The question makes no sense.

4. Senior Member
Join Date
Nov 2010
Location
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2,419
Originally Posted by Padilla616
Hey everyone,

My apprentice is about to take his Journeyman's test this Thursday through PSI. He got a question wrong on his PSI Practice Test and asked me for input. I'm embarrassed to say I couldn't see how they came up with their answer.

Q: What is the motor nameplate FLA rating for a 5 HP single-phase motor, 230 volt with an efficiency rating of 95% and a power factor of 90%?

A: 8 amps
B: 16amps
C: 19amps
D: 25amps

My apprentice chose the answer D, but the correct answer is C according to the practice test. Can anyone explain the formulas needed to come up with the answer? Any help would be appreciated!
Are you certain the question and answers are correct? I don't think the correct answer is listed. From a code standpoint the info about the PF and the efficiency is irrelevant and is just part of the question to confuse you. The code would require the use of Table 430.248 which would be 28 amps.

5. I just Googled a couple 5hp motors and checked the nameplates. One had an FLA of 22, the other 25 at 230 volts.

Besoeker's math makes total sense to me. I don't understand where the NEC came up with 28 amps.

6. Originally Posted by K8MHZ
I just Googled a couple 5hp motors and checked the nameplates. One had an FLA of 22, the other 25 at 230 volts.

Besoeker's math makes total sense to me.
Ok I guess that makes sense: its more of an electrical calculation question not an NEC question. I still think it is a horrible question to put on an electricians test because it would never be calculated that way. IT should have some wording to distinguish it from an NEC question.

7. Originally Posted by electrofelon
Ok I guess that makes sense: its more of an electrical calculation question not an NEC question. I still think it is a horrible question to put on an electricians test because it would never be calculated that way. IT should have some wording to distinguish it from an NEC question.
I think that 'FLA' should not be part of the question. Instead why not just ask what the current draw of the motor under a full load would be? The only reason I could think would be that somewhere in the course, 'FLA' was defined in a different manner than standard use.

8. Junior Member
Join Date
Jun 2015
Location
Muskegon, Mi, USA
Posts
16
All together the question did not make much sense to me, but I've never actually had to make that calculation before. Thanks for the quick replies and feedback!

9. Originally Posted by K8MHZ
I don't understand where the NEC came up with 28 amps.
The NEC is generous with amp ratings in the tables in 430 because FLA can vary between motors of the same horsepower and conditions of use vary greatly. If everything but the overload rating gets sized for worst case scenario then a motor can be swapped out with no danger to the premise wiring.

10. Junior Member
Join Date
Mar 2017
Location
Cloverdale,Va.
Posts
7

## FLA calculation

Originally Posted by Padilla616
Hey everyone,

My apprentice is about to take his Journeyman's test this Thursday through PSI. He got a question wrong on his PSI Practice Test and asked me for input. I'm embarrassed to say I couldn't see how they came up with their answer.

Q: What is the motor nameplate FLA rating for a 5 HP single-phase motor, 230 volt with an efficiency rating of 95% and a power factor of 90%?

A: 8 amps
B: 16amps
C: 19amps
D: 25amps

My apprentice chose the answer D, but the correct answer is C according to the practice test. Can anyone explain the formulas needed to come up with the answer? Any help would be appreciated!
Mike Holt covers this in a video called Motor Nameplate Full Load Amps. the formula is

(1x746)/(ExEFFxPF)

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