How we classified resistive , capacitive & inductive loads ? thanks

Status
Not open for further replies.
D

danishdeshmuk

Advanced Member level 1
Joined
Aug 17, 2011
Messages
426
Helped
35
Reputation
70
Reaction score
35
Trophy points
1,308
Activity points
4,001
How we classified resistive , capacitive & inductive loads ?

What are advantages & disadvantages of each of these ?

thanks
 

RESISTIVE LOAD (heaters and incandescent lights)

The voltage and current peaks coincide and are therefore in phase and the power factor is in unity.

INDUCTIVE LOAD (Motors and transformers)

With an inductive load the current waveform is lagging behind the voltage waveform, therefore, the voltage peaks and current peaks are not in phase. The amount of phase delay is given by the cosine of the angel (Cos) between the vectors representing voltage and current.

CAPACITIVE LOAD (Capacitors, wiring, cable)

The capacitive load has a current waveform which is leading the voltage waveform, therefore the voltage peaks and current peaks are not in phase. The amount of phase delay is given by the cosine of the angle between the vectors representing voltage and current.




Additional on that try to read this (about POWER FACTOR) :
Power factor - Wikipedia, the free encyclopedia
 

Can we calculate the power for capacitive load as well as for inductive load by just multiplying the voltage, current & power factor ?

thanks
 

Inductive loads exhibit higher Inductive reactance (XL) at higher frequencies and Capacitive loads exhibit higher capacitive reactance (XC) at lower frequencies. So, first calculate XL (=2.Π.f.L) and XC (=1/2.Π.f.C) at the frequency of your interest. Then calculation of power dissipation is these loads is same as power calculation of resistive loads.

Hope this helps...
 
Reactions: munzir

    M

    munzir

    Points: 2
    Helpful Answer Positive Rating
Calculating Reactive Power in AC Circuits

The reactive power is the power returned to the source by the reactive components of the circuit. This type of power is measured in Volt-Amperes-Reactive, abbreviated var.

Reactive power is calculated by using the voltage and current associated with the circuit reactance.

Since the voltage of the reactance is equal to the reactance multiplied by the reactive current, reactive power can be calculated by the formula:



Another way to calculate reactive power is to calculate the inductive power and capacitive power and subtract the smaller from the larger.



Either one of these formulas will work. The formula you use depends upon the values you are given in a circuit.
For example, find the reactive power of the circuit shown :



Since this is a series circuit, current (I) is the same in all parts of the circuit.




Read this in your spare time:
Inductive Reactance Tutorial

:wink:
 
When do we say or use the term impedance rather than resistance ?

Can we calculate output power (utilized power) by measuring the amperes measured by a normal AC clamp meter knowing the voltage ?

How to calculate the power factor then ? if not mentioned on the motor's plate or the device's plate

thanks a lot tpetar
 

Can we calculate output power (utilized power) by measuring the amperes measured by a normal AC clamp meter knowing the voltage ?
Click to expand...

Yes. Additional read material about current transformators in devices for measuring power.

How to calculate the power factor then ? if not mentioned on the motor's plate or the device's plate
Click to expand...

I send You material for inductive load. Motors are inductive load.

Here is other material :

Motor Efficiency Depends Upon Power Factor

Power Factor Correction
**broken link removed**
 

Attachments

  • Motor_PowerFactor_WP.pdf
    718.4 KB · Views: 193
Last edited:
When do we say or use the term impedance rather than resistance ?
 
Reactions: munzir

    M

    munzir

    Points: 2
    Helpful Answer Positive Rating
danishdeshmuk said:
When do we say or use the term impedance rather than resistance ?
Click to expand...

In a DC circuit, the ratio of voltage to current is called resistance. However, in an AC circuit this ratio is known as Impedance, Z with units again in Ohms. Impedance is the total resistance to current flow in an "AC circuit" containing both resistance and inductive reactance. If we divide the sides of the voltage triangle above by the current, another triangle is obtained whose sides represent the resistance, reactance and impedance of the coil. This new triangle is called an "Impedance Triangle"

Read all article what I give You:
Inductive Reactance Tutorial


Please read and this as new:
Resistance vs. Impedance
**broken link removed**

:wink:
 
Last edited:
Can a normal watt-hour meter measure the utilized power by the load (device) ?

thanks
 



thanks a lot

why wiring & cables are capacitive loads ?

What does it mean by " use motor cable which is shorter or of lower capacitance ? "
 

why wiring & cables are capacitive loads?
Click to expand...
Mutual capacitance is a elementary property of adjacent conductors. You can either take it as a fact or e.g. calculate the amount based on the known cable geometry and isolator permittivity.

What does it mean by " use motor cable which is shorter or of lower capacitance ? "
Click to expand...
You're apparently referring to a VFD inverter manual. Inverters usually have a maximum accepted cable capacitance.
 

thanks a lot, you're absolutely right . i'm referring toi a VFD inverter manual .... LENZE Servo Drive 9326

How to calculate or evaluate the maximum cable capacitance ?

thanks

---------- Post added at 19:10 ---------- Previous post was at 19:09 ----------

How to do that " calculate the amount based on the known cable geometry and isolator permittivity. " ? thanks
 

I found the below specification in a Siemens inverter operation manual.
In other words, they are not referring to exact capacitances rather than typical cable lengths.

Formulas for capacitance of parallel wires can be found in theoretical electrical engineering text books, see also Capacitance of simple systems in Capacitance - Wikipedia, the free encyclopedia The exact values for stranded, multi phase cable are of course a bit more difficult to determine. Thus I think, measuring it with a multimter is probably a more simple way.
 


What to measure with multimeter ? capacitance of each wire inside the cable ??
or of each cable used in the inverter ?

and how to do that ?

thanks
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…