Power calculation disagreement

Good afternoon,

I tried what I thought would be simple power calculations, but the calculations are not balancing.  It seems that I'm doing something fundamentally incorrect.  Here's a hypothetical situation that illustrates the problem.

There is a new 120/208 panel that has only one 2-pole breaker installed.  The load is 208 and the neutral is not used by the load.  The panel power meter shows line currents of 10, 10, 0.  The power factor is .90.  With the above readings, I believe the power for the panel (which represents only the one load) would be:

Average of line currents * line voltage * power factor * sqrt(3)

6.67 * 208 * .9 * 1.732 = 2,162 Watts

Then I go out to the field with my multi-meter and calculate power at the load:

Line current * line voltage * power factor (assumed to be same as panel)

10 * 208 * .9 = 1,872 Watts.

Why do I calculate ~15% lower power at the load?



asked 6/30/2018

0 Answers

Your Answer

In order to provide an answer to this question, you must Login

I am flagging this question because...

10 inform moderator flags remaining

I am deleting this question because...

I am flagging this answer because...

10 inform moderator flags remaining

Flagging a Post

You have already flagged this post. Clicking "Remove Flag" below will remove your flag, thus reducing the count by one as well.

I am deleting this answer because...

Introduction to Lighting

When looking at the design of a lighting scheme it is useful to have an understanding on the nature of light itself and some of the basic theory associated...

Lightning Protection and Earth Electrode Resistance

Most installations involve some form of lightning protection system which is connected to an earth electrode.  The function of the earth electrode is to...

IEC Document Designation

Often document control is dictated by project requirements, for example a particular organisation may have an existing numbering system. Existing company...

Hazardous Areas – IEC and NEC/CEC Comparison

Depending where in the world you work, you are likely following one of two standards International Electrotechnical Commission (IEC) National...

Material Properties

Everything physical in electrical engineering from insulations to conductors revolves around materials. Here we are listing common materials along with...

LED Replacement Light Bulb

The inventor of the first visible light-emitting diode makes history again this year as it begins to show customers a 40-watt replacement GE Energy Smart...

Power Factor

Power factor is the ratio between the real power (P in kW) and apparent power (S in kVA) drawn by an electrical load. The reactive power (Q in kVAr)...

Load Flow Study – how they work

A load flow study is the analysis of an electrical network carried out by an electrical engineer. The purpose is to understand how power flows around...

Voltage Levels to IEC 60038

The standard aims to consolidate AC and traction voltages within the industry and defines the following bands: band 1 - A.C. systems 100 V to 1...

Induction Motor Calculator

Just added a page to the tools, which will allow you to calculate the synchronous speed, slip and rated torque for an induction motor. Not a particularly...

Our website uses cookies so that we can provide a better experience.
To learn more about what cookies are and how to manage them visit AboutCookies.org