Brief Description of Voltage Drop Course

This is a four hour course on Voltage Drop and Calculations. The first 10 tests for this course consists of 10 questions each for a total of 100 questions. Test 11 has only four question but they are multipart requiring more complicated calculations. The eleven Final Tests must be taken and passed with a 70 per cent or higher score. Each time you submit a test the server grades, records and then sends the grade back to the test page for the student to see. 

Tests cannot be submitted for grading until after 1200 seconds (20 minutes of cumulative time.) The lapse time for each test is recorded at the server and so is the time that the test was submitted.  

After the recorded tests are completed and passed a link for the notification of completion permits the student to notify that they have completed the material. The notification of completion form is automatically emailed to when the submit button is clicked. After the notification is received by email the instructor reviews the records to ensure that the tests have been passed and the required time taking the tests is acceptable and payment has been made. The instructor then sends a certificate of completion to the student by email and updates the student's record for continuing education in the State of Washington L and I database for Washington persons and sends a certificate by email and US mail for Alaska persons. This is usually done within 24 hours after the notification of completion is received. 


This course covers the following:

Voltage drop for 2 wire DC, single phase 2 wire, 3 phase 3 wire and 4 wire circuits where loads are balanced and not balanced.

3 phase circular mil area of conductors to satisfy given conditions, maximum length for given conditions, circular mil ohms per foot, power factor using cosines, and many other variables associated with voltage drop.

How to use Tables 8 and 9 in Chapter 9 of the NEC are covered for finding voltage drop.

How to use a voltage drop calculator built into the Test 11 that does 8 different types of voltage drop problems at once for comparisons including those for power factors other than one.

How to perform segmented voltage drop as applied to R/V Park feeders.

How the Neher McGrath formula is used to develop equations for finding the actual operating temperature of conductors then finding the circular mil ohm resistance for that temperature.

Some subjects covered are:

1.  Voltage Drop can be lowered for phase to neutral by balancing the load.

2.  For underground installations voltage drop can be lowered by using 20 degrees C ambient instead of 30 degrees C.

3.  Segmented voltage drop calculations for R/V and mobile park Feeders can result in using smaller conductors.

4.  A Low Power Factor results in a much higher voltage drop for conductors larger than 4/0.



This course requires students to have some background in Algebra, Vectors, and Trigonometry. This course is mathematically intensive, but the various mathematical subjects are reviewed for any one that may have forgotten their math.