Short-circuit calculations using transformer and source impedance

An infinite bus short-circuit calculation can be used to determine the maximum short-circuit current on the secondary side of a transformer using only transformer...

PV Modules Part 2. Calculations, This Won’t Hurt—Much

DC Modules Output varies.  As addressed in the previous article in this series, the direct current output of a dc PV module varies with the...

Basic three-phase power measurements explained

Although single-phase electricity is used to supply common domestic and office electrical appliances, three-phase alternating current (ac) systems are almost universally used to distribute...

Load Calculations for Services and Feeders. Are we consistent on this...

Section 8 of the Canadian Electrical Code is absolutely critical to the Code users, as the accurate load calculations in accordance with this Section...

Voltage Drop Formulas

Voltage drop is only mentioned in some sections of the NEC as informational notes, and is required to be calculated in other sections of...

Service Equipment Labeling [ NEC 2017 100.16(B)] Part 2

Practical Example The following is a real-life example of a church supplied from a 208Y/120 VAC, 300 KVA, 3-phase pad mount utility transformer. The published...

Box Fill Calculations

One of the most frequently encountered Code violations, in my experience, would have to be those concerning box fill requirements. More conductors, devices, fittings,...

Service Equipment Labeling — NEC 2017 110.16(B)

Prior to the 2002 version of the National Electrical Code® (NEC®), incident energy and arc flash requirements were found in NFPA 70E, “Standard for...

100% vs 80%: Choosing the right OCPD solution

We make decisions every day, both personally and professionally, with our checkbook in mind.  When decisions are made to “value engineer” or cost out...

Calculating Short-Circuit Current

One of the most fundamental calculations made on a power distribution system is that which yields available short-circuit current. The September – October 2012...