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23rd March 2015, 03:00 AM  #1 
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Join Date: Feb 2012

Do real people actually use radians/sec instead of Hz
Outside of academia I have NEVER seen people talk in terms of radians/sec when discussing AC signals. Why do so many books use radians/sec and why do most spice simulators have radians as the default unit?

23rd March 2015, 03:04 AM  #2 
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Join Date: Feb 2004
Location: Silicon Valley

Depends on whether you're doing an integration, where radians might work better...

23rd March 2015, 03:06 AM  #3 
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23rd March 2015, 07:25 AM  #4 
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Join Date: Feb 2001
Location: USA

The values for power supply capacitance can be realistically determined by a consideration of the numerical value of W C R where W is the line frequency (377 rad/sec), C is the power supply capacitance, and R is the load resistance. An WCR value of 10 yields about 10 per cent ripple (pk.pk. ) and a value of 100 has about two percent. Below 10, the power supply will have serious problems and values of about 100 will achieve diminishing performance returns. The minimum value then, for each of the four power supply capacitors should be about 3,000uF and the maximum about 30,00OuF. Capacitances above this value may cause diode bridge failure due to turnon surges and are not recommended.
(http://www.passdiy.com/pdf/a40.pdf) 3,300µF x2 for one channel at 8Ω with 60hz line (3,900µF for 50hz), double for 4Ω, double again for 2Ω. Example: Crest CA9 has a tiered supply and 120,000µF total capacitance. This is 15,000µF per channel, per tier, the 10% ripple point. Remember, stored energy increases with the square of the voltage, so a 3,300µF cap with 100V on it stores 4x the energy that a 3,300µF cap with 50V on it stores. radian per second = W f*2Pi=W 377 (60hz) 314(50hz)
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23rd March 2015, 12:27 PM  #5  
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Quote:
J/K. When doing math with phasors, as in standard AC analysis, calculus is converted into algebra. Differentiation is multiplying by jW, integration is dividing by it. Frequency almost always needs to be in radians in the math. The equations tend to read better (fewer factors of two pi to keep track of). 

23rd March 2015, 01:28 PM  #6  
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Quote:
I was just working on an article where I decided to consider the audience and present things in terms of actual Hz and not normalized frequency. The complex math automatically does the phase book keeping, you would do well to understand both approaches and remain unconfused. Next folks will ask why sometimes we just throw away the imaginary part.
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23rd March 2015, 01:31 PM  #7 
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Did you ever take Prof. Kraut's class? I still don't quite get the "magic" residue stuff.
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23rd March 2015, 04:39 PM  #8 
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Join Date: May 2007

Radians are the natural way to measure angle if you are doing mathematics, therefore radian/sec are the natural way to measure rotation. People in academia use mathematics, and write (and read) books. That is why you will see radians used in books.
If you want to use some other measure then you will always be needing to convert to radians anyway  that is why you get lots of 2pi scattered around EE equations. Use radians and the 2pi mostly disappear. 
23rd March 2015, 05:05 PM  #9 
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Join Date: Nov 2005

On the other hand a lot of old practical manuals expressed frequency as cycles per second, c.p.s., and if that's the only point you're trying to convey, Hz became more handy.

23rd March 2015, 06:30 PM  #10 
diyAudio Moderator

I have a spreadsheet calculator for conversion between cycles per second and Hertz. Works great!
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