# What is time delay an AC and DC current and how do I calculate it (in terms of period)?

Discussion in 'Homework Help' started by hmcdo43, Mar 5, 2016.

1. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
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I have graphs such as (there is a factor of 250 implemented on current for ease of comparison). I am asked at what frequency produces the smallest time delay (in a range of 200Hz to 2000Hz). However I do not know how to define time delay as the internet cannot give me a straight answer. I know that by logic it is either:
- Time taken to reach maximum magnitude of amps
- Time take for the magnitude of amps to stabilize
- The difference in phase shift between current and voltage

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2. ### WBahn Moderator

Mar 31, 2012
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What and how you measure all depends on what, exactly, is important.

So, what is important?

3. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
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the time delay is important?
The time delay is important?

4. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
How can I know?

First, what time delay are you talking about, and second, is it important for YOUR application?

5. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
8
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Okay, for the graph above is there a time delay present within the current?
Because I am unsure of what to look for when looking for a time delay.

6. ### #12 Expert

Nov 30, 2010
16,685
7,323
Look at the graph. Is one axis labeled, "time"?

7. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
8
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yes the x-axis is labelled time

8. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
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Are there different types of time delay?

9. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,500
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It seems to me that you need multiple graphs. Your minimum frequency is 200 Hz. Your maximum frequency is 2000 Hz (2 kHz). So first step would be to do multiple graphs, every 400 Hz to start with: 200, 600, 1000, 1400, 1800, 2000. This will give you idea where the delay is smallest. Once you know the delay is smaller at the specific interval, then you can do multiple plots for that interval.

It seems to me that you are looking at the delay between voltage and current. If you are using simulation software, there should be traces that you can place on the simulated oscilloscope and they will give you values of time. Normally people place traces on some easy to track points on the graphs, for example peaks. You have current peak next to the voltage peak, put one trace on current peak, record the time, put trace on the voltage peak next to the current peak, record the time. Subtract one time from the other, now you know the delay between current and voltage.

Also. Looking at the pic you uploaded, you need to let the signals stabilize, it seems to me that in that pic 0 to 0.0075 seconds is unstable. After 0.01 second signals seem to be stable.

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10. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
8
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THANKYOU!!

okay i am not using simulation software do you know of any i could use easily?
Im currently just working on excel

11. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,500
511
You can do it in Excel too, it is just a lot more work.
Did your instructor give you set of data to plot?

You can look at the very last set of peaks. Since you are in Excel, you know exactly the time when each peak is occurring.

12. ### WBahn Moderator

Mar 31, 2012
18,087
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Well, in your very first post you mentioned three, so I would say yes.

Where did the data you are plotting come from? I know you said you are using Excel. Did you get a bunch of raw data or do you have equations that you used to generate the data?

My guess (and that's all it really is) is that you are asked for the frequency that gives the smallest absolute time delay difference (equivalent to phase shift) between the voltage and current waveforms (essentially the time difference between peaks). If this is the case, then you want to look far enough into the data that the waveform as stabilized reasonably well.

Do you have different data sets for different frequencies? Or do you have a parameter that you can use to change the generated data?

If so, then you can built up an equation that gives the time difference for the data at a given frequency and then build up a table of time differences as you change the frequency.

13. ### hmcdo43 Thread Starter New Member

Mar 4, 2016
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I believe I am on track now thanks heaps

14. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
Good luck to ya!