The output impedance can be programmed/ adjusted within the range of (R=2~200mOhm, L= 2~200uH). I can turn off the output impedance as well.
The program automatically disabled the output impedance if there are a regenerative load connect to the power.
The output power of this power supply is 15KVA, therefore I think it can supply the high current as I want.

 

I connected a resistor 100 Ohm (103 Ohm to be exactly), 1.2KW to the power supply and measure the current. With applied voltage 150V, the current is around 1.45 A.
Then I connect that resistor in series with my circuit. The measured current is around 1A which is quite close to the simulation result as in the picture below.
Still I did not figure out where the problem come from.
Could anyone give me some advice?
Thank you.

 

I connected a resistor 100 Ohm (103 Ohm to be exactly), 1.2KW to the power supply and measure the current. With applied voltage 150V, the current is around 1.45 A.
Then I connect that resistor in series with my circuit. The measured current is around 1A which is quite close to the simulation result as in the picture below.
Still I did not figure out where the problem come from.
Could anyone give me some advice?
Thank you.

And what is the current and voltage when you drive just a 15 ohm resistor with your supply?

And have you accounted for increasing resistance of the coil as it heats up?

 

And what is the current and voltage when you drive just a 15 ohm resistor with your supply?

Now, I do not have that high power resistor (15 Ohm, 1.5KW). I am looking for it and test it later.
However, according to the datasheet of the power supply, it has the power of 15KVA. Therefore, I believe it can provide enough power.
But, I will purchase the resistor and test again to make sure.

 

As I mention in my first post, when I apply the power (150 VAC) and desired frequency to the coil and capacitor in series.
The current through the coil should go up to around 9A as in simulation.
However, it do not go that high. It is just around 4A.

9A through a closely packed 1.5mm wire?

 

The wire is not the big issue I think. I run this system at 10A for more than 1 hour. The coil temperature is around 50 oC. In addition, we have the cooling system for the coil.

 

The wire is not the big issue I think. I run this system at 10A for more than 1 hour. The coil temperature is around 50 oC. In addition, we have the cooling system for the coil.

How about posting a picture of this setup and some scope pictures

How and where are you measuring the coil temperature?
Is this an air core coil?

 

What are you plugging the amplifier into? 240V mains?
Or through a step-up or isolation transformer?

 

Obviously at least one of your assumptions is wrong or the circuit would behave like the simulation: your supply, your components, your hook up or your measurements. You need to find out which before you can fix the problem.

Is the one pole of your supply grounded as you show in the schematic? And your scope is grounded, i.e. plugged directly into the same mains?
Assuming you have measured the output of the amplifier, not the amplifiers displayed output, and it is indeed 150V at all load variations.
And assuming you have checked the current probe to be sure it is reading properly at these low frequencies: e.g. by measuring AC current at two relevant frequencies (30Hz 300Hz) via current probe and o-scope voltage probes across a known resistor. Then suggestion...

Use Ch1 for source voltage, Ch2 other side of coil, Ch3 current probe. (Adjust scope trigger for CH1 zero phase reference)
With source at 75V and at resonant frequency record frequency and amplitude and phase of all three channels and Ch2-Ch1.
Repeat at a frequency above and below resonance where the current amplitude is 1.41 and 0.71 of resonant amplitude.
Repeat all measurements at 150V source.

Watch for drift - record initial (after a few seconds) and after drift stops.

Organize and report results in table format.

 

The attached picture is my coil system.

How and where are you measuring the coil temperature?

I use the infrared digital thermometer to measure the coil temperature.

Is this an air core coil?

Yes, it is an air coil, as you can see in the attached picture.

What are you plugging the amplifier into? 240V mains?
Or through a step-up or isolation transformer?

Yes, the power supplier are connected to the 240 VAC main power line

Obviously at least one of your assumptions is wrong or the circuit would behave like the simulation: your supply, your components, your hook up or your measurements. You need to find out which before you can fix the problem.

Is the one pole of your supply grounded as you show in the schematic? And your scope is grounded, i.e. plugged directly into the same mains?
Assuming you have measured the output of the amplifier, not the amplifiers displayed output, and it is indeed 150V at all load variations.
And assuming you have checked the current probe to be sure it is reading properly at these low frequencies: e.g. by measuring AC current at two relevant frequencies (30Hz 300Hz) via current probe and o-scope voltage probes across a known resistor. Then suggestion...

Use Ch1 for source voltage, Ch2 other side of coil, Ch3 current probe. (Adjust scope trigger for CH1 zero phase reference)
With source at 75V and at resonant frequency record frequency and amplitude and phase of all three channels and Ch2-Ch1.
Repeat at a frequency above and below resonance where the current amplitude is 1.41 and 0.71 of resonant amplitude.
Repeat all measurements at 150V source.

Watch for drift - record initial (after a few seconds) and after drift stops.

Organize and report results in table format.

I will try to measure all the data and show you next time.
Thank you so much

 

"I use the infrared digital thermometer to measure the coil temperature."

OK, so that is a surface measurement. What is the cooling mechanism?


That is quite the interesting rig you have there. Am I seeing 3 or 4 coils?
This is not the simple coil I imagined. For what purpose is this equipment, may I ask?

Is the "coil" and test in question just one of those rings, operated with the others turned off and open circuited or do we have some inter coil coupling going on here?

Keep in mind that apparent resistive losses are not just from the wire resistance but also eddy current losses or any mechanical work the coil may be doing - intentional or otherwise.

 

Is the "coil" in question just one of those rings, operated with the others turned off and open circuited
or do we have some coupling going on here?

A coil including two rings which is opposite each other.
Those coils are used to generate the magnetic field, which is quite similar to the MRI system.

 

A coil including two rings which is opposite each other.
Those coils are used to generate the magnetic field, which is quite similar to the MRI system.

The eddy current losses in the frame I would expect to be significant so your equivalent R for your circuit is significantly higher than the DC wire resistance.

Are these two coils driven in series or parallel? And I assume the fields are not bucking each other?

 

The eddy current losses in the frame I would expect to be significant so your equivalent R for your circuit is significantly higher than the DC wire resistance.

Are these two coils driven in series or parallel? And I assume the fields are not bucking each other?

Yes, that may be true. Because, I previously used the DC power to operate the system and everything work well. However, DC power cannot work with this resonant effect. Therefore, I try to use AC power and resonant effect to operate the system with high frequency. And here I am, still in trouble.
The coil can be connected in series or parallel, depending on what kind of magnetic field we want to produce.
May changing the frame material solve the problem? The frame material now is aluminum.

 

Yes, that may be true. Because, I previously used the DC power to operate the system and everything work well. However, DC power cannot work with this resonant effect. Therefore, I try to use AC power and resonant effect to operate the system with high frequency. And here I am, still in trouble.
May changing the frame material solve the problem?

Yes, you could change to a high resistance material. Take a plate of the material and move it in and around the coil field and see how the current changes.

For this device to fullfill its function I assume you need to supply an AC field with a certain constant flux density and over a range of frequencies. Correct? Why not use a constant current source instead of a voltage source?

 

For this device to fullfill its function I assume you need to supply an AC field with a certain constant flux density and over a range of frequencies. Correct? Why not use a constant current source instead of a voltage source?

It can work well with all function with DC power. Actually, what I do with the power supply in DC mode is program it to keep the current contanst by changing the applied voltage, which is quite similar to the current source you said.

 

It can work well with all function with DC power. Actually, what I do with the power supply in DC mode is program it to keep the current contanst by changing the applied voltage, which is quite similar to the current source you said.

Yes that is how CC sources work. Did you change the voltage manually or program the power supply for constant current? I believe it has the capability.

So if you don't need an AC field then I don't see the problem, just use DC CC.

 

Yes that is how CC sources work. Did you change the voltage manually or program the power supply for constant current? I believe it has the capability.

So if you don't need an AC field then I don't see the problem.

I programmed the power supply for constant current.
But the problem is that I want to operate the coil as high frequency, which cause the quick increase of coil's impedance.
Therefore, I want to use the resonant effect to cancel the impedance of the coil as resonant frequency, which DC power does not have?!

 

I programmed the power supply for constant current.
But the problem is that I want to operate the coil as high frequency, which cause the quick increase of coil's impedance.
Therefore, I want to use the resonant effect to cancel the impedance of the coil as resonant frequency, which DC power does not have?!

That's what I thought until you said the following:

"It can work well with all function with DC power."

Regardless, if the unit can do CC with AC then that solves the problem. Unless it simply can't supply enough voltage to get the current you need at high frequencies due to high resistive impedance.

Also your circuit simulation is probably too simple for your coil arrangement. Probably some sort of transformer model would better capture the behaviour of the coil and its interaction with the frame.

 

I mean the functions with low frequency. Sorry for that