Best method of entry.
02-23-2016, 03:26 PM
Post: #1
 NewMC Junior Member Posts: 9 Joined: May 2014
Best method of entry.
What is the best way to enter the following integral into the Prime?

1/2pi * integral of i(wt) dwt from alpha to beta (this is formula for average current in 1/2-wave, single phase rectifier with inductive load)

Known from i(wt) formula: i(wt)=6.78*sin(wt-0.646)-2.67e^-(wt/0.754)
Given alpha=0.785 and setting wt=beta and i(wt)=0 in above equation I find beta=3.785.

I want to make sure I'm inputting the integral correctly to confirm my answers.

Thank you
02-24-2016, 12:23 AM
Post: #2
 roadrunner Senior Member Posts: 306 Joined: Jun 2015
RE: Best method of entry.
I'm not sure I understand your question. Do you want to find beta such that the integral from alpha to beta of i(wt) is zero? If so, this is what I did:

There are many solutions, one of which is about 6.446126.

Here is a plot of that solution:

If I am misunderstanding , please clarify.

02-24-2016, 04:03 PM (This post was last modified: 02-24-2016 04:04 PM by NewMC.)
Post: #3
 NewMC Junior Member Posts: 9 Joined: May 2014
RE: Best method of entry.
Thanks for the response roadrunner. Alpha was given and I have already solved for beta > pi by setting wt=beta (in i(wt)) and i(wt)=0. Now I'm just looking for the best way to input into the calculator the following in order for the calculator to solve it:

integral i(wt) dwt from 0.785 to 3.785

So: integral (6.78*sin(wt-0.646)-2.67e^-(wt/0.754)) dwt from 0.785 to 3.785

Does this help to clear up what I'm looking for?

It looks like this is close to what you've done but when I input the first line from your picture: ii:=(wt)->(xxx) in Function/CAS I get an unspecified error, when I choose OK it puts the cursor between the first w and t in the statement. Maybe there is something wrong with my key sequence for the input? Keystrokes: alpha, i, alpha, i, shift, Vars, :, enter, shift, ., (), alpha, w, alpha, t, right on directional pad, shift, 9, right arrow, (), then input expression.
02-24-2016, 07:51 PM
Post: #4
 Terje Vallestad Member Posts: 145 Joined: Dec 2013
RE: Best method of entry.
Hi,

Is this what you mean?

∫(6.78*sin(wt-0.646)-2.67*e^(-wt/0.754),wt,0.785,3.785)

Returns around 12.797 with radians set

Use the template on the "C" button to assist with inputting the integral

Cheers, Terje
02-24-2016, 10:56 PM
Post: #5
 roadrunner Senior Member Posts: 306 Joined: Jun 2015
RE: Best method of entry.
(02-24-2016 04:03 PM)NewMC Wrote:  when I input the first line from your picture: ii:=(wt)->(xxx) in Function/CAS I get an unspecified error, when I choose OK it puts the cursor between the first w and t in the statement

Do you have the latest firmware version? Try it this way:

ii(wt):=-2.67*e^(-1.32625994695*wt)+6.78*sin(wt-0.646)

Or just cut and paste the line above into the emulator.

then type or cut and paste:

∫(ii(wt),wt,0.785,3.785)

You should get the same answer as Terja