Need help with phaser diagram

Thread Starter

apache4trak

Joined Jul 26, 2020
9
to be honest im lost with last three questions can someone point me to a straight for tutorial or video to explain phaser diagrams first please and how to calculate cos . ive done a and b but c onwards im stuck and need guidance for dummies .

task 5.PNG
work so far

a)impedance Z = 100.0032 ohms current 0.009999amps
b) voltage drop Vc = 0.0079992 , Voltage drop Vr = 0.9999
 

Thread Starter

apache4trak

Joined Jul 26, 2020
9
sorry i was wrong i use 200k instead of 2k

a) = 128.062485 ohms - 0.0078 amps
b) = voltage drop Vc = 0.624v Voltage drop Vr = 0.78v
 

Thread Starter

apache4trak

Joined Jul 26, 2020
9
update

capacitive reactance

1 / 2 x pi x 2000 x 0.000001= 80ohms

Z = square root of 100squared + 80squared

= Sqroot of 10000 + 6400 = 128.06ohms

current = 1v / 128.062485 ohms = 0.0078 amps

voltage drop Vc = 0.62

Voltage drop Vr = 0.78

tan(-1) x 0.8 = 38.6 degrees I leads voltage
 

Thread Starter

apache4trak

Joined Jul 26, 2020
9
No i do not understand to be honest but slowly learning , i think .

ok great so ill include angles in my answer .

So if the phaser diagram above is ok , all i need now to complete is the last one.

e) show the voltage and current mathematical sinusoidal expressions
 

WBahn

Joined Mar 31, 2012
26,068
One problem you are going to have is that the diagram doesn't properly specify the reference phases for any of the voltages, including Vs. Since there are three different voltages each of which can have one of two different polarities and be consistent with the diagram, there are eight different defensible solutions. So the first thing you need to do is clearly define the polarities of the voltages you are going to be working with. Are you familiar with the passive sign convention?
 

Thread Starter

apache4trak

Joined Jul 26, 2020
9
No im not @WBahn , i took a electrical engineering online course , enjoyed all the rest of the 9 topics but im on last unit last assignment with 3 week till deadline and they drop the hardest one on me .
 

Thread Starter

apache4trak

Joined Jul 26, 2020
9
@Zeeus thanks i am getting there ill update my work tomorrow . Yeah read loads of book on motor and electronics but
bit admit I am a bit lazy with the maths , I have got 2 books on order now Electrical fundamentals and basic electronic theory . Unfortunately I am having to rush this last unit of my last assignment to avoid having to repay .
 

WBahn

Joined Mar 31, 2012
26,068
Voltages are always differences in potential between two points. Whether a voltage is positive or negative depends one whether you are taking the difference of side A relative to side B or the other way around. You need to clearly indicate which you are doing for every voltage you are using. It is a simple matter of putting a '+' sign on one end and (optionally) a '-' sign at the other.

The passive sign convention says that the voltage across a passive component is defined as the voltage on the side the defined current enters relative to the side that it leaves. For active devices the reverse is often taken to be the case as that generally results in the fewest negative quantities at the end of the day. So taking that into account, we have the following:

phasorproblem.png
You should also start tracking your units throughout your work. It will save you LOTS of grief, both now and later.
 
Top