The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
Texas_Ranger 8
Trumpy 8
sparkyinak 7
Who's Online
1 registered (sparkyinak), 220 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#128632 - 08/07/03 09:34 PM Reactive power/Energy?
PowerMonitor Offline
Junior Member

Registered: 08/07/03
Posts: 2
Loc: Gandhinagar,Gujarat,India
What meaning of reactive power in electrical system?and how it creating and where it goes?
please explain me inductive load and capacitive load properties which creates reactive energy.
Thanks.

Top
#128633 - 08/08/03 10:27 PM Re: Reactive power/Energy?
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
To answer PowerMonitor's post: (or at least try to...)

 Quote:
What's the meaning of reactive power in electrical system?


Reactive Power is the "Other" power flowing within the complete Apparent Power figure.

True Power (Wattage) + Reactive Power (Volt-Amps Reactive, or VARs) = Apparent Power (Volt-Amps, or VA).

The AC Power can be figured by applying the Pythagorean Theorem, created by the Triangle dude, Pythagoras

This is a simple formula, which is:

A²+ B² = C²

If you have values for any 2 of the 3 sides, this calc will give value for the unknown side.

Looking at the AC power triangle per function, here's the breakdown:

SIN: True Power (Wattage),
COS: Reactive Power (VARs or KVARs if 1000 or more),
TAN: Apparent Power (VA or KVA if 1000 or more).

The Power Factor is the relationship between the True Power and the Apparent Power.

For a simple example, let's say the power figures are:

True Power (SIN) = 4 Watts,
Reactive Power (COS) = 3 VARs,

This would result in an Apparent Power of 5 VA, which equals out to be an 80% Power Factor.

Here's how it was done:

C² (TAN) = A² (SIN) + B² (COS)

4² = 16 (A),
3² = 9 (B)
16 + 9 = 25 (C)

Square Root of 25 = 5, so C (TAN) = 5

Power Factor was figured by getting the percentage between True Power and Apparent Power.

4 (watts) is 0.8 - or 80% of 5 (VA), so the Power Factor in this example is 80%

 Quote:
and how it creating and where it goes?


This may sound funny, but VARs are created by the Reactive Elements themselves, when an AC is applied to them.
VARs shuttle between the Reactive Elements of an AC Circuit - and are stored within them.

A simple example using a single core, single layer Inductor (coil) and a step down Transformer would show the Reactive Power stored in the Inductor, with Reactive Currents "Shuttling" between the Transformer and the Inductor.

 Quote:
please explain to me inductive load and capacitive load properties which creates reactive energy.


This is a little beyond simple examples and descriptions - especially using only text! Here, you're best options are to read a few Tech Manuals in order to get the basic ideas of all the principles and such.

In a nutshell, one has an effect on the AC wave, which causes the Current to LAG behind the Voltage, at a certain degree.
This one would be - of course - Inductive Reactance (XL).
The other Reactance effects the AC wave so the Current LEADS the Voltage, at a certain degree.
This one would be - of course - Capacitive Reactance (XC).

The thing about Reactances is they cancel each other out (generally speaking), so to combat an excessive LAGGING (XL) problem, XC is added to the circuit. The same goes for the opposite.

When figuring a Circuit's Impedance (Z), the total Reactance (X) will be a result of subtracting the lower Reactance from the Higher Reactance.
Example:

XL = 10 Ohms, XC = 8 Ohms.
Total X = 2 Ohms (Inductive)
Z = total Reactance, so Z = 2 Ohms

When applying a fixed pure Resistance (R) into the total Z figure, use the Pythagorean Theorem once again. In this case, figure the total Reactance before running the calc.
Example:

R = 4 Ohms,
XL = 9 Ohms,
XC = 6 Ohms.



    [*]Find total X: 9 - 6 = 3 Ohms.

    [*]R² = 16, X² = 9.

    [*]R² + X² = 25

    [*]Square Root of 25 = 5


Circuit's Impedance (Z) = 5 Ohms.

p.s. see any kind of a relationship here???

Applying Inductive and Resistive elements in a series circuit across different types of power supplies will result in different readings.

Example:

3 Ohm Inductor + 4 Ohm Resistor in series;

Connected to DC power supply: Total = 7 Ohms.
Connected to AC power supply: Total = 5 Ohms.

 Quote:
Thanks.


No problem!
Just hope this stuff answers your questions!

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#128634 - 08/09/03 06:19 AM Re: Reactive power/Energy?
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
That’s a good, concise overview, Scott. Supporting text may be something like www.ibiblio.org/obp/electricCircuits/AC/AC_11.html, but it’s written from a college-freshman-lecture-with-300-other-students perspective. {Be very careful about relying solely on slasher-grade capsulized web-based technical material.}

Bench testing various meter forms will reinforce these concepts and better tie them to real-world equipment and measurements that energy and demand metering make.

[Fair warning, though—when nonsinusoidal waveforms are introduced, it a while new ball game with a more complex set of definitions.] The EEI handbook is a root reference.




[This message has been edited by Bjarney (edited 08-09-2003).]

Top
#128635 - 08/11/03 01:18 AM Re: Reactive power/Energy?
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Bjarney,

Thanks for the reply.

Hope the info I presented in this thread is useable! The topic(s) are kind of advanced, and my responses are kind of ... basic!

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals