90 degrees phase shift
in [DSP]
|
From: Giuseppe Sbarra on 1 Jul 2005 12:27 Hi, I'm an hold analog engineer , actually developing a DSP based application and I need to change of 90 degrees the phase of a signal on the range of 50 - 250 Hz aving the system a 200uSec sampling rate. I have considered the Hilbert FIR filter but for the moment I cannot get it to work not even reducing the sampling rate. In particular I nedd to phase shift by 90 degrees a signal (voltage) respect to another (current) in order to calculate the instantaneous REACTIVE power by a simple multiplication. Any suggestion would be very appreciated. Thanks everybody
From: Tim Wescott on 1 Jul 2005 12:58 Giuseppe Sbarra wrote: > Hi, > I'm an hold analog engineer , actually developing a DSP based application > and I need to change of 90 degrees the phase of a signal on the range of > 50 - 250 Hz aving the system a 200uSec sampling rate. > I have considered the Hilbert FIR filter but for the moment I cannot get it > to work not even reducing the sampling rate. > In particular I nedd to phase shift by 90 degrees a signal (voltage) respect > to another (current) in order to calculate the instantaneous REACTIVE power > by a simple multiplication. > > Any suggestion would be very appreciated. > Thanks everybody > > I'm not sure why your hilbert transform wouldn't be working so I can't comment on it. On the other hand, if you were to compute the RMS value of the voltage and current and compute the mean power then the reactive "power" should be Vrms * Irms - real power. That's how I'd do it. -- ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com
From: Pierre de Vos on 1 Jul 2005 17:33 "Tim Wescott" <tim(a)seemywebsite.com> wrote in message news:11cath1cpvl3i29(a)corp.supernews.com... > Giuseppe Sbarra wrote: > >> Hi, >> I'm an hold analog engineer , actually developing a DSP based application >> and I need to change of 90 degrees the phase of a signal on the range of >> 50 - 250 Hz aving the system a 200uSec sampling rate. >> I have considered the Hilbert FIR filter but for the moment I cannot get >> it >> to work not even reducing the sampling rate. >> In particular I nedd to phase shift by 90 degrees a signal (voltage) >> respect >> to another (current) in order to calculate the instantaneous REACTIVE >> power >> by a simple multiplication. >> >> Any suggestion would be very appreciated. >> Thanks everybody >> >> > I'm not sure why your hilbert transform wouldn't be working so I can't > comment on it. > > On the other hand, if you were to compute the RMS value of the voltage and > current and compute the mean power then the reactive "power" should be > > Vrms * Irms - real power. > > That's how I'd do it. > Surely that is'nt true V*I=S=sqrt(P^2 +Q^2) so reactive power = Q = sqrt(S^2 - P^2) > -- > ------------------------------------------- > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com
From: Tim Wescott on 1 Jul 2005 17:52 Pierre de Vos wrote: > "Tim Wescott" <tim(a)seemywebsite.com> wrote in message > news:11cath1cpvl3i29(a)corp.supernews.com... > >>Giuseppe Sbarra wrote: >> >> >>>Hi, >>>I'm an hold analog engineer , actually developing a DSP based application >>>and I need to change of 90 degrees the phase of a signal on the range of >>>50 - 250 Hz aving the system a 200uSec sampling rate. >>>I have considered the Hilbert FIR filter but for the moment I cannot get >>>it >>>to work not even reducing the sampling rate. >>>In particular I nedd to phase shift by 90 degrees a signal (voltage) >>>respect >>>to another (current) in order to calculate the instantaneous REACTIVE >>>power >>>by a simple multiplication. >>> >>>Any suggestion would be very appreciated. >>>Thanks everybody >>> >>> >> >>I'm not sure why your hilbert transform wouldn't be working so I can't >>comment on it. >> >>On the other hand, if you were to compute the RMS value of the voltage and >>current and compute the mean power then the reactive "power" should be >> >>Vrms * Irms - real power. >> >>That's how I'd do it. >> > > Surely that is'nt true > > V*I=S=sqrt(P^2 +Q^2) > so > reactive power = Q = sqrt(S^2 - P^2) > Well, I'll be dipped in shaving cream. Thank you for finding my error. It's still an easier calculation than the Hilbert Transform, though. ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com
From: Erik de Castro Lopo on 1 Jul 2005 18:11 Giuseppe Sbarra wrote: > > Hi, > I'm an hold analog engineer , actually developing a DSP based application > and I need to change of 90 degrees the phase of a signal on the range of > 50 - 250 Hz aving the system a 200uSec sampling rate. > I have considered the Hilbert FIR filter but for the moment I cannot get it > to work not even reducing the sampling rate. > In particular I nedd to phase shift by 90 degrees a signal (voltage) respect > to another (current) in order to calculate the instantaneous REACTIVE power > by a simple multiplication. If you are using an FIR hilbert transform, you need to remember that there is a transport delay in the FIR filter and you need to delay the unfiltered version as well. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam(a)mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ Saying Python is easier than C++ is like saying that turning a light switch on or off is easier than operating a nuclear reactor.
|
Next
|
Last
Pages: 1 2 3 4 5 Prev: Who Invented the Z Transform Next: What is the most effective way to do a zoom FFT |