90 degree phase shift for capacitor heating

me

from

peak-

whatever

resistor

should

NEUTRAL

between

differently:

two

CCW?

I would stronlgy suggest adding a safety isolation step down transformer to derive the signal. (for safetys sake obviously)

Colin =^.^=

"Industrial Electrician"

The simplest way to get a 90 degree phase shift relative to the AC supply is to use a transformer with a secondary that has a centre tap and connect that centre tap to ground. Then you will have two, safe low voltage AC supplies to use. One will be in-phase with the AC supply and the other in exact anti- phase.

( I suggest you get a small ( ie 20 or 30VA) *toroidal* transformer with a

THEN, connect one end of 3.3 kohms resistor to one 7.5 volt supply and one end of a 1uF ( plastic film ) capacitor to the other, join the remaining cap and resistor leads, this point creates a 7.5 volt supply that is 90 degrees shifted.

Slight adjustments to the resistor or cap value will get the result spot on at 50 or 60 Hz.

The problem with using the AC supply as an input signal is the waveform is not a perfect sine wave - however it will likely be close enough or your purpose.

Good luck testing the temp rise of the filter caps - make sure to monitor the air ambient near the caps as well as the actual cap body temp.

....... Phil

Yes.

Not a bit. AC power conversion amplifiers can handle any power factor, including 100% capacitive, 100% inductive, and nonlinear (cheap) switching power supplies.

I know how to stay safe. This is in a controlled lab condition. We do things that we would b=never do in a real-world installation.

In addition, the amplifier input has an input transformer with a

Anti-phase is 180 degrees, not 90 degrees.

Ah. That is where you are getting the 90 degree shift?

So you are saying I got the component values wrong? That is the part I am unsure about, but I calculated 10 microfarads, not 1. I believe that the

-3db point (con=rner frequency) has to be at least 1/10 of my 50/60Hz.

"Industrial Electrician"

What you describe is a fatal shock hazard to any operator.

Bad thing in a electrician if he wants to stay alive.

Yours is the mad sparkys' damn dangerous way to do a very simple job.

....... Phil

Putting the capacitor to the hot line will give you a nearly 90 degree phase lead, but will also differentiate any noise spikes on the line and pass them to the resistor with little attenuation. Connecting the capacitor at the neutral side will integrate the line voltage, causing an almost 90 degree phase lag, but will low pass filter any noise, giving you a much cleaner sine wave signal.

A 10 uF capacitor has about 265 ohms impedance at 60 Hz. As long as the series resistor has a much higher resistance than that, the phase shift (across the resistor) will approach 90 degrees.

In order to have about 10 volts appear across the capacitor impedance, you need about .038 amperes to pass through it. A resistor of about

Then you could connect a 100k pot across the capacitor, and use the wiper to adjust the output voltage to exactly whatever value you wanted that any fraction of what is across the capacitor. That high resistance load will alter the phase shift almost not at all, but will provide a low enough impedance to drive the 1 meg input impedance with little sag (measure the final voltage while connected to the input, or substitute a 1 meg load across the pot to set the voltage).

It would be a very good idea to have an isolation transformer between the line and this circuit, so the output low side has no voltage with respect to the amplifier common.

I only had time for a quick test before we closed down Friday, but I did have time to try it both ways, and the noise is much, much lower doing it the way you suggested. Thanks! My oscilloscope trigger circuit thanks you as well. ;=)

That makes sense. Just to see if I understand, the above relates to what I read about the -3DB point because the bigger resistor moves that frequency down, and if I then lowered the signal frequency I would not only moving closer to the -3DB point but also lowering the impedance of the capacitor. Am I getting all of this right?

I see how that works. Just to see that I understand, that also means that the resistor/capacitor phase shift has a voltage loss, and that someone who needs the phase shift at the original voltage would need to use another technique such as an operational amplifier based circuit. Am I getting this right?

That's a great idea. All of my high wattage pots are much smaller in resistance but using a parallel pot like you suggest beans that I can use a regular pot. That's very helpful.

This is a temporary setup on a wooden bench, and I have separate

Isolation transformers are very useful if you are poking around inside a TV, but when working with high current and high voltage systems, you are far safer by enclosing everything in an earth-grounded case, having neutral connected to earth ground instead of floating, and never energizing the circuit without having everything closed up inside earth- grounded finger-proof grounded conduits and boxes. If you or "Phil Allison" disagree, please describe, in detail, the exact path that you think current will take through the human body from a system using the industry-standard grounding system I am describing. I am open to being shown that I am wrong, but not without a good explanation showing why I and everyone else in my industry is wrong.

I only had time for a quick test before we closed down Friday, but I did have time to try it both ways, and the noise is much, much lower doing it the way you suggested. Thanks! My oscilloscope trigger circuit thanks you as well. ;=)

That makes sense. Just to see if I understand, the above relates to what I read about the -3DB point because the bigger resistor moves that frequency down, and if I then lowered the signal frequency I would not only moving closer to the -3DB point but also lowering the impedance of the capacitor. Am I getting all of this right?

I see how that works. Just to see that I understand, that also means that the resistor/capacitor phase shift has a voltage loss, and that someone who needs the phase shift at the original voltage would need to use another technique such as an operational amplifier based circuit. Am I getting this right?

That's a great idea. All of my high wattage pots are much smaller in resistance but using a parallel pot like you suggest beans that I can use a regular pot. That's very helpful.

This is a temporary setup on a wooden bench, and I have separate

Isolation transformers are very useful if you are poking around inside a TV, but when working with high current and high voltage systems, you are far safer by enclosing everything in an earth-grounded case, having neutral connected to earth ground instead of floating, and never energizing the circuit without having everything closed up inside earth- grounded finger-proof grounded conduits and boxes. If you or "Phil Allison" disagree, please describe, in detail, the exact path that you think current will take through the human body from a system using the industry-standard grounding system I am describing. I am open to being shown that I am wrong, but not without a good explanation showing why I and everyone else in my industry is wrong.

I only had time for a quick test before we closed down Friday, but I did have time to try it both ways, and the noise is much, much lower doing it the way you suggested. Thanks! My oscilloscope trigger circuit thanks you as well. ;=)

That makes sense. Just to see if I understand, the above relates to what I read about the -3DB point because the bigger resistor moves that frequency down, and if I then lowered the signal frequency I would not only moving closer to the -3DB point but also lowering the impedance of the capacitor. Am I getting all of this right?

I see how that works. Just to see that I understand, that also means that the resistor/capacitor phase shift has a voltage loss, and that someone who needs the phase shift at the original voltage would need to use another technique such as an operational amplifier based circuit. Am I getting this right?

That's a great idea. All of my high wattage pots are much smaller in resistance but using a parallel pot like you suggest beans that I can use a regular pot. That's very helpful.

This is a temporary setup on a wooden bench, and I have separate

Isolation transformers are very useful if you are poking around inside a TV, but when working with high current and high voltage systems, you are far safer by enclosing everything in an earth-grounded case, having neutral connected to earth ground instead of floating, and never energizing the circuit without having everything closed up inside earth- grounded finger-proof grounded conduits and boxes. If you or "Phil Allison" disagree, please describe, in detail, the exact path that you think current will take through the human body from a system using the industry-standard grounding system I am describing. I am open to being shown that I am wrong, but not without a good explanation showing why I and everyone else in my industry is wrong.

(snip)

All but the capacitor part. The impedance of a capacitor foes up as frequency goes down. Xc=1/(2*pi*f*C)

At the -3db frequency (where Xc=R) the phase shift is 45 degrees, at frequencies much higher than this, the phase shift approaches 90 degrees. Operating where a capacitor has an impedance of 265 ohms, in series with a 6000 ohm resistor is far enough above the -3db frequency that the approach to 90 degrees is pretty close.

Yes. this technique involves an essential voltage loss.

(snip)

Very well.

"Industrial Electrician"

Isolation transformers are included inside EVERY electronic and electrical device where human contact with external wiring is possible - as is the case with your 90 degree phase shifted "signal generator".

Using an isolation step-down transformer means you AVOID working with a dangerous high voltage system in the first place.

A. The previous low voltage (ie 90 degree phase shifted supply) jumps to

NOW:

Stop being such a conceited, bloody ass !!

A small isolation transformer and one R and one C network method is far CHEAPER and well as enormously SAFER than your asinine scheme.

........ Phil

Nothing of any importance. The system will stop working, but the fact that it is fully enclosed in earth-grounded conduit and boxes makes it impossible for the now-hot neutral to harm a human. Your rejection of the basic safety scheme used in all modern electrical wiring (earth grounded boxes and conduit enclosing a neutral that is earth-grounded only at the service entrance and a hot that is protected by a fuse or breaker) is based on ignorance. Your suggestion that an isolation transformer be added and the neutral be allowed to float is dangerous and illegal in most municipalities. Stay away from AC power, please; you are sure to hurt someone with your lack of knowledge and refusal to learn from those who know what they are talking about.

There already exists a hot wire with 220VAC on it inside the grounded conduit and boxes. Your belief that an open neutral that creates another wire with 220VAC on it inside the grounded conduit and boxes is a safety issue is magical thinking; both hot and neutral are fully protected from contact with a human, as is the capacitor and resistor that comprises the phase shift network. Your inability to describe, in detail, the exact path that you think current will take through the human body says it all. Until you can describe that path, all your blustering and magical thinking will only lead you farther astray.

Use of personal attacks to hide an obvious lack of technical rigor in your claims noted. Bozo Filter now engaged.

Plonk.

"Industrial Electrician"

Dumbfuck sparkie assholes like YOU have no training in or comprehension of basic electrical safety.

The use of an isolation step down *removes* the need for a connection to neutral to exist to guarantee safety - since loss of a neutral connection merely disables the transformer.

Don't have the SLIGHTEST idea why electronic appliances have isolation trasnformers inside ?

Likely you will electrocute yourself real soon.

I sincerely hope you do not kill a co-worker.

....... Phil