×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Need a 8000A-10,OOO amp magnetic field? help?

Need a 8000A-10,OOO amp magnetic field? help?

Need a 8000A-10,OOO amp magnetic field? help?

(OP)
Our customer wants a magnetic field around some bus bars for testing.  Could anyone help me with advice on how to do this.  I have some 10,000:5 C.T.s....could I push 5 amps into them and if so, at what voltage...could I use a variac to adjust the field level?

thanks

RE: Need a 8000A-10,OOO amp magnetic field? help?

You aren't going to push 5A into the secondary of a 10,000:5 CT and get 10,000 out the primary.  It just ain't gonna happen.  Saturation will see to that.

RE: Need a 8000A-10,OOO amp magnetic field? help?

Remember the magnetic field isn't amps it's amp-turns.

You can increase the field with amps (hard to come by) or turns (relatively easy).

Get a bunch of big arc-welding cable and an arc-welder. Wrap your target and go for the gusto.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Need a 8000A-10,OOO amp magnetic field? help?

An arc-welder isn't ideal for that. A spot welder has a lot more current available. But usually for very limited time (spots take about half a second to make).

On the other hand, if you have a 20 kA spot-welder and run it at 25 percent load, it can probably be run long enough for your experiment. And, as smoked says, use as many turns as you need to produce the ampere-turns.

BTW: Is it an AC or a DC field that you need? There are both kinds of spot-welders. Some may even be switchable.

Gunnar Englund
www.gke.org

RE: Need a 8000A-10,OOO amp magnetic field? help?

The CT approach sounds reasonable to me.  

Saturation is avoided as long as the impedance of the  the high-current loop is small enough.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: Need a 8000A-10,OOO amp magnetic field? help?

Keith's suggestion for multiple loops may or may not work depending on what aspect of the field the customer is trying to recreate.   You can easily get the same field magntiude but the flux distribution will be different than for the busbar carrying 10,000A.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: Need a 8000A-10,OOO amp magnetic field? help?

(OP)
Your assumption is correct on the saturation of the copper.  Out of the two CT's we were able to push only 900A at 277V.  The CT's are rated 400V, so we could have gotten more out of them, but not even close to the 7000A we are looking for.

The time restraint is 90 seconds.  

We have gathered p additional driver CT's from around the plant to help push the power, but we believe we are constrained by the available power in the lab.  We would need a new line run into the lab.  

I think I would need three welders to run a three phase circuit?
How would I calculate the cable turns around the copper?  I have a 3000A source.
thanks

RE: Need a 8000A-10,OOO amp magnetic field? help?

If this is a one off test and you need to do it then speak with one of your local generator suppliers - say Aggreko or the like and ask them. Using a gen set supplying a transformer you should be able to generate your current levels required for the test. Just make sure that you have adequate insurance !

Some panel builders use a genset and transformer to generate around 40-60kA short circuit withstand tests.

Rugged

RE: Need a 8000A-10,OOO amp magnetic field? help?

Yo drax! What are you trying to test for?  We still don't know what magnetic configuration you need.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi drax,

Copper doesn't saturate: the iron core does. You will need a very large CT with a high kneepoint voltage to be able to run it in reverse as a useful high current source. the principle is fine but, as ePete has correctly said, keeping the impedance of the high current path low enough could be tricky. I have an old Class X CT off a grid transformer put to one side for the day when I get round to building a heavy current injection source. The core weighs more than I do: the secret with this sort of thing just comes down to sheer volume of iron - well strictly cross-section area of iron! - to avoid core saturation.

You should able to get hold of a primary injection test set capable of delivering 2kA or maybe 4kA into a low impedance load. If you use a mains-powered PITS, there should be no problem in paralleling two of them if they are fed from the same mains supply phase. They are fairly common pieces of equipment in the utility industry.

Ruggedscot is also potentially on the right path. We have done similar tricks using a 2.5MVA  11/0.415kV transformer fed from a 415V generator connected to the 11kV winding. The 415V winding effectively becomes a continuous rated 26.5V 3500A source. You could cheerfully overload it for a short period without causing any significant problem to the transformer.

I'm a little puzzled what your customer is trying to achieve: is this for fault withstand tests, or for magnetic compatability with other equipment, or some other purpose? You are looking at some fairly high power test rigs which will be quite costly to set up - is there an easier way to achieve the same objective?

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hello drax
Let's do the numbers on your CT.
Ratio 10,000:5 or 2000:1
At 277 volts, your open circuit secondary voltage will be 0.1385 volts.
The impedance of the secondary path includes buth the bus bar impedance and the impedance of your connecting cables.
If the impedance of your cable is three times the impedance of your bus bar the voltage drop across the bus bar will be only 1/4 of the total voltage, or 0.1385/4 = 0.034625  
Current:
With 900 amps the primary current would be 900/2000= 0.45 amps.
Suggestions;
If possible mount the CTs on the bus bars and use bus bar jumpers to short the ends of the bus bars. If you can mount two CTs in series on each bus bar you will get more voltage to work with.
Saturation:
Saturation is exceeding the allowable flux densiy of the iron. Flux density is dependant on amp turns. Depending on the class of the CT you may be able to go to 10 amps or more without saturating. The limiting factor will be the insulation strength of the CT winding. It is probably good for 10 amps or more without saturating.
Fun with numbers: this is to give you a feel for what you can change and what the results will be.
Impedance. Use the bus bars to form the return path for each other. If you can reduce the impedance by a factor of 4, your current should go up to 4 x 700 = 2800 amps. (Factor 4)
Voltage: At 400 volts you current should increase from 900 to 400/277 x 700 = 1300 Amps. (Factor 400/277=1.44) At 1000 volts (If the insulation doesn't fail) the current will be 900/277 x 1000 or 3250 Amps. (Factor 1000/277=3.6)
2 CTs in series = 1800 amps (Factor 2)
If you reduce your impedance by a factor of 4, increase your voltage by a factor of 3.6, use 2 CTs per phase for a factor of 2, Your total current increase will be:
900 Amps X 4 X 3.6 x 2 = 26,000 amps.
Your project may be possible if you can reduce the secondary circuit impedance and increase the secondary voltage.
You are nowhere near saturation, your secondary voltage is too low and your secondary impedance is too high.
There have been several suggestions to use a generator. The reason is two-fold. First to avoid drawing too much current from the utility. Second to avoid inrush currents.
If you get this setup to deliver 10,000 amps to the bus bars under steady state conditions, the energisation inrush may be over 50,000 amps and that could quite easily convert your bus bars into ballistic misiles.
Use a generator or a variac to bring the voltage up slowly.
respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

(OP)
Thanks for all of your help, it looks like a generator is the way to go.  This test is for magnetic reaction around equipment.  One engineer stated this about looping welding cable around the bus bar, do you guys agree?

"It doesn't make sense to me based upon my college days as well as a few years of practice. There is very poor coupling a low frequencies, which is why iron cores are used. If the welder output was a RF, then this might work, but inductive reactance becomes a huge factor. There is an impedance which has to be overcome. The generator has to be able to generate sufficient voltage to drive the desired current through the impedance. The AC version of Ohm's law V=IZ  (Z= R +JX =R=J2PiL) applies. Z is mostly inductance. If a capacitor bank of sufficient size was available to counteract the inductive reactance then we would only have to overcome the resistive voltage drop in the system.  That's still doesn't say we can accomplish what we need with what we have. I still think you will need to go somewhere that can generate 12kA of current for 1 minute."

RE: Need a 8000A-10,OOO amp magnetic field? help?

The use of a generator is probably your best bet.  You'd need a big one to handle the 10,000A, say a 3750kVA transformer with a 208V secondary, and a 12kV (anything from 10 - 15kV) primary.  Then, feed that primary with a 480V generator.  If the transformer had a 12470V primary, the primary current would need to be 1/60 of your 10,000A or 167A.  The secondary, the 208V side, would be essentially short circuited, and you would control the generator output to produce the voltage necessary to drive 167A into the primary of the transformer.  All will be well, the transformer will be vastly over rated voltage wise, but running right at its ratings current wise, the generator will not need to exceed 480V to produce the 167A.  In theory you might be able to get that out of a 150kW generator, but because that short circuit will be essentially all reactive, you may need to go to a 250kW or even 300kW generator to keep the reactive current within the generator capability curve.  Then again, it may take a 500 or 750kW generator just to energize that 3750kVA transformer.  If you could put a 10,000A breaker on the secondary of the transformer, you could have the transformer connected to the generator as the generator voltage builds and then not have any inrush.  You'll get your current on the 208V side of the transformer, but no voltage to speak of; but 10,000A is nothing to be trifled with, even at close to zero volts.

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hello davidbeach
A question. The op stated a time constraint of 90 seconds. If we went to 5 minutes for a safety factor, could he safely use smaller transformers for a 5 minute test?
Would a variac and a bridge rectifier be adequate for manual field control of the generator output?
Thanks
respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi David,

Do you have transformers rated 3750kVA / 208V in the US? That seems a huge rating for an LV transformer. What is the typical impedance? We rarely see much over 2.5MVA at 415V because switchgear becomes expensive and fault level gets very high. Our typical impedances are about 6% or so at 2.5MVA which keeps things to a reasonable level.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Scotty,  I didn't look to see if a 3750 with 208V secondary was actually available.  I would imagine that the 3750 would be something well above base rating to get there.  The rating isn't the real problem, the problem is the ability to carry 10,000A and there is very little designed for those kinds of numbers.  It might well be more practical to parallel several smaller transformers, say five 750s.  His 90 seconds is way beyond fault testing setups that use capacitor discharge to get very high currents/voltages; no stored energy for a 90 second test.

RE: Need a 8000A-10,OOO amp magnetic field? help?

Agreed - the interconnections will be difficult to arrange at 10kA on anything not designed for the purpose. That was the reason for my suggestion of using paralleled primary injection sets - probably easier to arrange than a gang of utility transformers.

The Programma range of test equipment - now swallowed up into GE - has had a couple of additions since I last looked. The Oden primary injection set can now deliver up to 22kA at 4.3V, which I find pretty amazing. There are numerous smaller variants. Page 8 of 10 in the following link shows the big 'uns.

http://www.gepower.com/prod_serv/products/electrical_test/en/downloads_new/down_en/test_inj_testing/odenat_en.pdf

As commercially available equipment appears to be out there, I suggest using it. High energy tests using temporary rigs are best avoided if possible - too much scope for things going wrong in the hands of the inexperienced.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Scotty, interesting.  He'd have to use the 3 minute rating, for which that unit is rated 7700A, close but not quite the lower limit of his stated range (but maybe close enough).  I shudder to think what a unit like that might cost though.

RE: Need a 8000A-10,OOO amp magnetic field? help?

I guess you could assume the current rating for a time of 90 seconds is greater than that for 3 minutes, so it might scrape by at 10kA for 90s. The applications guys would know. It is by far the most powerful commercially produced PITS I have seen, and I bet it costs an absolute fortune - their smaller sets aren't exactly cheap!

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Respectfully fellas. He got 900 amps out of the CTs and he only wants 7000.  Consider reducing the impedance and increasing the voltage on the CTs. posibly two CT's in series. (With 10,000 amp CT's he needs more voltage not more current.)
he needs 7000/900 more than he has now. That's only a factor of less than 8.
He can probably get a lot of that by eliminating the secondary cables and using bolted bus bar connections. He will not be overloading the current transformer's KVA capability as long as the primary current is below 5 amps.
The insulation on the CT primary should easily withstand close to 2000 volts.
Why does a transformer over heat and fail on over voltage? The rated current has been exceeded. As long as the primary current is below 5 amps, we are not saturated and we are not overheating the transformer.
The huge transformers that have been discussed will be putting out about 1 or 2 volts instead of 480 volts. That's an under utilization factor of 240:1 or more. That's OK if you have the transformer in the yard and can borrow it.
Let's look at what he does have. Reduce the secondary impedance and increase the primary voltage and the 8:1 factor we need is probably within reach with the transformers on hand.
respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

Respectfully ScottyUK I notice on another thread you have suggested that voltages in the range of 1000 Volts may be applied to the secondary of a CT. At 277 volts the OP achieved 900 amps. At 1000 he should have 3250 amps. That is almost halfway to the 7000 amps he needs. Reduced impedance or two CT's in series and he has it. (Yes series not parallel. His current is being limited by the available voltage, not the impedance.)
Respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi waross,

The 1000V kneepoint is high but not out of the question for a Class X CT. They are designed specifically to have a very high kneepoint voltage - essentially lots of high grade iron in the core to give a low mag current and low core flux. Common CTs have a much lower kneepoint.

Strictly it is not voltage than we are short of, but magnetic flux. Increasing the flux is achieved by circulating more current, which is achieved by applying more voltage, up to the point where the core saturates. The only options to avoid saturation are: bigger core, or more turns, or higher frequency. The idea of series CTs is interesting - essentially it gives the effect of a bigger core. The easiest way to picture it is that for a given core at a given frequency, the volts/turn is a constant. If the volts/turn is not large enough to circulate rated current, the core will saturate.

The big distribution transformer I suggested using would give about 27V on open circuit rather than 1V or 2V - they are fairly easy to rent over here in the UK. I'm pretty sure  such a transformer would withstand a 200% overload for 90 seconds - the thermal mass is huge. The big unknown is the mechanical integrity of the winding and leadouts - they are designed to withstand massive short duration faults, not smaller sustained faults. This is essentially a fault-level test we are discussing.

You have made a very good suggestion: "Let's look at what he does have". Even the big primary injection set is going to take more power than the 277V supply to his lab can handle.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi ScottyUK
Thanks for the response.
I found out years ago working on series lighting circuits that when using constant current transformers all the normal circuit characteristics were turned upside down. The only thing that you could depend on was ohms law.
This situation has many similarities.
The CTs are capable of the current, low voltage is the problem. If we can increase the voltage and reduce the voltage required we have a good chance of doing it.

I have a question, ScottyUK, about saturation tests.
Am I right in assuming that the test current is in excess of 5 amps (or rated secondary current) at the knee of the saturation curve?
If so we may be able to increase the voltage significantly above 277 volts.

If the original poster will let us know what he was using for hardware when he pushed 900 amps through the bus we can start making valid suggestions. If the circuit was cable connected and if it is possible to change to bolted bus connections we are well on the way.
Another point, with one bus CT the current will travel the length of one bus bar and return on another. With 3 CTs in star the voltage required from each CT is about half. That should translate into double current right there.

I understand that the original poster has several 10,000 amp CT's available. The problem of course is the very low voltage generated when these are used in reverse.
I think we can address this issue on two fronts. First, by using the bus bars directly instead of connecting with cables we can reduce the circuit impedance.

In response to my own last post, if you have a big transformer in the yard you can abuse it, but the rental agency will frown on you renting a transformer with the intention of forcing 200% of rated current through it for however short a time.
Respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hv a coil of 10,000 turns on a core and pass 1A. U will have 10000 amp turn field.But what is the application your customer is needing this?

RE: Need a 8000A-10,OOO amp magnetic field? help?

kptx,

Very easy to say, much less easy to do! Care to design the core?

Waross,

At the kneepoint the CT will hopefully only be drawing a few tens of mA, maybe a couple of hundred at the absolute outside on a horrible cheap CT. Once past the kneepoint the current starts rising at an exponential rate (well, maybe not truly exponential but bloody quickly: the mathematical analysis is gonna be complicated!). You may not be able to raise the voltage more than 10% above the kneepoint before all the rated current is used for magnetising current.

Quote:

the rental agency will frown on you renting a transformer with the intention of forcing 200% of rated current through it

Only if you tell them!

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

And who would tell them???

RE: Need a 8000A-10,OOO amp magnetic field? help?

Find a company in your area that tests low voltage circuit breakers using primary injection. Look for a NETA company. Typical breaker test sets put out up  50,000 amps.  A new or different power supply from the utility would nto be needed, since most  test sets operate on 240 V or 480 V power (or equivalent.)

The actual power requirement is relatively small, as long as the voltage drop in the loop of cable or bus is reasonable, say 5 volts or less.  (50 kA @ 5 V = 250 kVA).  

A test set with standard CT will never make it. The impedance of the primary circuit changes by the square of the turns ratio when viewed from the CT secondary.  With just 0.5 ohms of impedance in your high current circuit and a 10,000:5 CT (2000/1 ratio) the secondary impedance will be  2 meg ohms.

A 480 VAC supply could push about 0.25 milliamps into a 2 megohm impedance and get about 1/2 amp output on the high side of the 1000/5 CT.

I would be concerned about generating a "10,000 amp" field for a test. Without a gauss meter to measure the field, how do you know what field strength actually is applied to the device under test?  The field strength is very dependent on the conductor configuration around the device.  

For example, you could get high current by using a coax confuguration using two aluminum pipes, one inside the other, and welded or bolted together at one end.  This  low impedance circuit could easily carry "10,000 Amps" for 90 seconds.  But the external magnetic field would be close to nil, since current in the two pipes would cancel each other.  My point is make sure the test set up gives your client what they need, not what they say.

RE: Need a 8000A-10,OOO amp magnetic field? help?

Get a junk transformer with a good 115 volt or 230 volt primary on the inside. Cut the secondary off. (don't disassemble the transformer) Loop one turn of bus bar through the core. Using a variable transformer, slowly increase the voltage to the junk transformer primary.
If you don't have enough current add turns.
I have done this and it works great.

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi CarlPugh
I like it.
In the original test the popster got 900 amps at 277 volts.
That would be a primary current of 900A/10,000A x 5A = 0.45A.
At 277 volts that would be about 125 VA. We need about 8 times the current so that would be 64 times the VA.
That makes our requirement 8 KVA. To allow a safety margin for the extra bus bar, I would suggest looking for a transformer in the range of 15KVA to 25 KVA.
For testing the mechanical strength of  busbar mounting you should use three transformers and three phase power.
For testing the magnetic effects around the busbars, whatever makes the customer happy. Hopefully you can get by with single phase testing.
I would expect that single phase currents will be the "worst case" for adjacent magnetic effects. You will not get any field cancelling from the other phases. That's the argument that I would use to try and avoid the extra expense of three phase testing. Likewise testing with the current out on one bar and back on an adjacent bar will probably subject those two bars to greater mechanical stress than a three phase current. The currents will be in phase rather than 120 deg. displaced.
Bear in mind that a momentary outage in the source current during the test may cause a transient inrush that can easily apply enough force to blow the busbars out of the enclosure.
Doing a 7000 amp test on bus bars with a mechanical capability of less than 30,000 or 50,000 amps would make me nervous.
If you are using more than one transformer in any configuration, be very carful to avoid open circuit primaries.
I hope you have the customer sign off on the testing method in case the test destroys the equipment.
respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

waross,

What is the difference between Carl's vandalised power transformer and a large CT driven in 'reverse'? Both are just iron cores wound with copper windings. Whether they are used in a CT or VT mode is down to the way they are applied. The transformer laws apply to all transformers - the significant one here being the impedance transformation being proportional to the square of the turns ratio. rcwilson has already mentioned this.

rcwilson,

I'm curious where you can easily get hold of a 50kA breaker test set - they are certainly not common over in the UK. The Programma unit I mentioned earlier is the largest I've seen. I'd be interested to have a look at one if you know of a manufacurer & model.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi ScottyUK
I agree with you 100%
Electrically, there is probably not much difference.
The main difference is possibly in availability and in the ease or difficulty of adding an extra turn or two on the high current side. Depending on what's on hand, the choice could go either way. We don't know if the OP's CTs are bar type or window type.
Do you concur with my KVA suggestions, SkottyUK?
respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hi waross,

Your arithmetic seems to make sense, but assuming the 'secondary' - the high current path - remains a constant impedance it will take 8x 277V i.e. 2.2kV primary voltage to drive the full 10kA through the secondary. The core does not have enough cross-section to allow application of such a voltage assuming the frequency is maintained constant.

The relationship between flux and voltage is proportional if we assume constant frequency. A ferrous core can only operate at a certain flux density prior to saturation, so if the flux doubles the magnetic cross section of the core must also double to avoid saturation. Note that 'flux' and 'flux density' are absolutely not interchangeable terms.

The point at which saturation occurs in the CT in question is a bit unknown - if the kneepoint is 400V then saturation is probably around 450V - 500V. It varies with different CT types. With that assumption for saturation, the core is probably about one-fifth of the required cross-section. If the larger core were available it would need an HV supply to drive the required current.

It will be interesting to try reducing the number of 'primary' - low curent - turns on the available CT so that saturation occurs just above operating voltage. This would make maximum use of the core by running it at rated flux density, and reduce the 'secondary' impedance as seen from the 'primary' side, causing more current to flow in both. I have to go to work now so I haven't time. Maybe later!

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: Need a 8000A-10,OOO amp magnetic field? help?

Hello ScottyUK
I think that we are pretty much in agreement. With a 400 volt rated CT, we may be able to get to twice 277V. That would push the 900 amps achieved by the OP up to 1800 amps.
I am sure that our secondary current is limited by the available secondary voltage so two CTs in series will push the current from there up to 3600 amps. We don't yet know how the OP has connected the CTs to the bus bars. WE don't know if the CTs are bar type or window type. If he has been using cables, and if it is possible to change cable connections to bus bar connections, he may be able to cut the impedance of the secondary circuit in half, at which point he will have 7200 amps. The OP was trying for 7000 amps.
I think we are safe in saying that it is theoretically possible to get 7,000 or 10,000 amps out of the high current side of a 10,000:5 CT but the extremely low voltage makes it quite dificult to arrange a circuit with low enough impedance.
Respectfully

RE: Need a 8000A-10,OOO amp magnetic field? help?

Quote (waross):

I think we are safe in saying that it is theoretically possible to get 7,000 or 10,000 amps out of the high current side of a 10,000:5 CT but the extremely low voltage makes it quite difficult to arrange a circuit with low enough impedance.

If the 5A side of the 10,000:5 CT is fed at 5A and limited to 600V - reasonable numbers - the impedance on the 10,000A side of the CT can not be allowed to exceed 1.2 micro ohms.

I'm not sure you can even come within an order of magnitude or two of 1.2 micro ohms.  At 10,000A, that circuit will have a total voltage drop of 12 mV (millivolts).

RE: Need a 8000A-10,OOO amp magnetic field? help?

It is probably worth pointing out that a CT fed from a mains power source doesn't exhibit normal CT behaviour. It is effectively just a normal power transformer with a large step-down ratio. It might prove beneficial to draw out the circuit using the classic transformer model and refer all the parameters to the high current side: source impedance, CT leakage reactance, CT winding resistance, load resistance, etc. The problems should then become apparent.

----------------------------------
  I don't suffer from insanity. I enjoy it...

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources