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Join Date: Jul 2017
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STS Heat Trace Reactor

09/12/2017 6:03 PM

Hello guys. so I got a STS Heat Tracing system (skin effect) installed on a 15km pipeline carrying refined crude oil residuum. the heat trace itself is single phase 1570V. but it is supplied from a three phase transformer 415/1570V 50Hz. because the system is single phase, it uses a load balancer circuit to distributes and balances the current on all three phases (see poorly drawn circuit).

http://i66.tinypic.com/f9i6np.jpg

so now, the reactor L is damaged, completely burned. the capacitors are ok. my questions are:

- Has anyone seen this kind of circuit before? how does it work exactly?

- Can it be modified in anyway to make it work temporarily until we get the new reactor (the residuum will solidify inside the pipeline which is a huge problem).

- can I supply the load (STS) directly from two phases of the transformer (remove C1 and L)? assuming it can take the load, does using only 2 phases affect the transformer?

- can I use an old transformer as a reactor? connecting only one winding in the place of the reactor?

Thanks.

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#1

Re: STS Heat Trace Reactor.

09/12/2017 7:36 PM

Here is a copy of your circuit. (You can paste pictures in with the little camera gizmo on the panel above.)

The three phases are 120 degrees apart. A capacitor can shift the current ahead by up to 90 degrees (ideally) and an inductor can shift the current back by up to 90 degrees (ideally) with respect to the voltage.

I haven't used this circuit, but I think the idea of this circuit is that the L2 current will be advanced by the capacitor and add to L1 and be retarded by the inductor and add to L3. Note that if the rotation of the source is not L1, L2, L3 this would not work. And, of course, the current is not shifted 120 degrees.

This document might help:

"A Method for Balancing a Single-Phase Loaded Three-Phase Induction Generator"

file:///C:/Users/Richard/Downloads/energies-05-03534.pdf

file:///C:/Users/Richard/Downloads/energies-05-03534.pdf

Here's another approach: If your load can be driven by DC, a 3 phase bridge could rectify the 3 phase AC and drive the load and be fully balanced.

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#4
In reply to #1

Re: STS Heat Trace Reactor.

09/13/2017 12:54 PM

I like the simplicity of the three-phase rectifier. Perfect answer. Simple and maintains phase balance.

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#6
In reply to #1

Re: STS Heat Trace Reactor.

09/13/2017 6:06 PM

I dont think STS work with DC? I'm not sure. I will look it up but if I were to use this I need high voltage and current rectifiers 2000v 200A rated. Are those easy to find?

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#8
In reply to #6

Re: STS Heat Trace Reactor.

09/14/2017 7:52 AM

Only to those with a willingness to look for them.

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#10
In reply to #6

Re: STS Heat Trace Reactor.

09/14/2017 2:03 PM

Apparently, it does have to be AC, is there a preferable frequency, or is 50 or 60 Hz optional for skin-effect heat-tracing?

You could probably make use of "new" GaN transistor technology to make the power requirements easier to achieve.

Now that I think about it, you should re-consider the choices to be made, and probably go with 3-phase supply, two phases shifted w.r.t. the remaining phase, thus arriving at single phase output.

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#11
In reply to #10

Re: STS Heat Trace Reactor.

09/14/2017 9:34 PM

It works on 1570v 50Hz. But 60Hz is okay too.

what if I disconnected the load balancer. I mean remove the two capacitors and the inductor and connect the load to L1 and L3 directly (see drawing). The current drawn by the heater is about 135A. The question here is, can I take only two phases from the 415/1570v transformer and leave the other phase L2 disconnected? What is the effect on the transformer?

The transformer primary is 415v 600A delta

secondary 1570v 150A delta

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#12
In reply to #11

Re: STS Heat Trace Reactor.

09/15/2017 9:06 AM

I think Solar Eagle already addressed the point of disconnecting the middle phase.

It will work, but I would not expect optimal results, as if you were using a transformer set up specifically designed for the task at hand, i.e. with the load balancer operating.

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#7
In reply to #1

Re: STS Heat Trace Reactor.

09/13/2017 9:17 PM

Yeah sts is works only on AC supply because it is based on skin effect which only observed with AC current....

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#9
In reply to #7

Re: STS Heat Trace Reactor.

09/14/2017 10:55 AM

Okaaaay . . .

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#13
In reply to #7

Re: STS Heat Trace Reactor.

09/15/2017 4:44 PM

It will work with 2 phases giving 1570 V AC. Rated transfo current = 150A, Heater 135 A. But check that the balancing is not to protect generators, which do not like unbalanced loads. It may be that the HV load is negligible compared to generator size anyhow.

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#2

Re: STS Heat Trace Reactor.

09/12/2017 8:30 PM

I think I would disconnect the middle lead, then try to add some btu's....possibly you could speed the pump up a bit...maybe add an auxiliary portable heater midway down the pipeline....possibly you could raise the voltage a bit...

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#3

Re: STS Heat Trace Reactor.

09/13/2017 5:39 AM

Your power supply uses a technology more than 70 years old. If it works let it be, but if it gets broken again, it would be better to think of something better. Currently there are power converters way cheaper, smaller, more reliable, and power factor does not depend on the load.

Weather you want the converter to control the amount of energy delivered or you want it to always work at full power is up to you. My company does custom made power converters, but you probably can find something similar in your location.

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#5

Re: STS Heat Trace Reactor

09/13/2017 1:50 PM

As pointed out by Rixter, you could enjoy much better control by opting for a 3-phase bridge rectifier with DC output.

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