High Voltage Withstand Tester AC/DC

[Danny]

I have a brief to design and build a HV test truck with the following
specs:

AC 75kv @100mA, 35kV@400mA
DC 40kV@400mA, (-20kV)-0-(+20kV) @ 400mA
also 300vac @ 30 amps for induced testing of 415/11kV transformers
variable (from the regulator)
my head is spinning at the possibities. I think that it'd be elegant to
use 1 transformer with 2 secondaries. i could utilise the fact that
both 240v and 415v @ 63amperes are available for the source supply. I
am considering utilising a doubler circuit for the split supply DC
supply as well as for the single ended DC supply by just moving the
earth point. Mind you for the 75KVac I'd need to get a high volts
transformer anyway so maybe a full wave rectified with centre tap?. 1
of the problems that I'm having is calculating the primary VA's for
secondary VA's for various rectifier (& doubler) circuit dc outputs. It
seems that there are cost benifits/penalties if there is a dc flux
component thus needing more core iron to avoid saturation (but how
much??) and likewise if both ends of the winding need to be insulated
for HV rather than just one(also...how much??). I'd sure appreciate a
bit of wisdom on how to approach this.

many thx in advance

Danny

 

[John G]

This is a professional design problem that has been addressed many times
by real engineers.
If you have to come here fore advice you are way way way out of your
depth

GET professional advice before you kill someone , maybe yourself.

I have a brief to design and build a HV test truck with the following
specs:

AC 75kv @100mA, 35kV@400mA
DC 40kV@400mA, (-20kV)-0-(+20kV) @ 400mA
also 300vac @ 30 amps for induced testing of 415/11kV transformers
variable (from the regulator)
my head is spinning at the possibities. I think that it'd be elegant
to
use 1 transformer with 2 secondaries. i could utilise the fact that
both 240v and 415v @ 63amperes are available for the source supply. I
am considering utilising a doubler circuit for the split supply DC
supply as well as for the single ended DC supply by just moving the
earth point. Mind you for the 75KVac I'd need to get a high volts
transformer anyway so maybe a full wave rectified with centre tap?. 1
of the problems that I'm having is calculating the primary VA's for
secondary VA's for various rectifier (& doubler) circuit dc outputs.
It
seems that there are cost benifits/penalties if there is a dc flux
component thus needing more core iron to avoid saturation (but how
much??) and likewise if both ends of the winding need to be insulated
for HV rather than just one(also...how much??). I'd sure appreciate a
bit of wisdom on how to approach this.

many thx in advance

Danny

This is a professional design problem that has been addressed many times
by real engineers.
If you have to come here for advice you are way way way out of your
depth.

GET professional advice before you kill someone , maybe yourself.

News groups are really for asking isolated questions that someone with
other experience may be able to help with.

They are not for teaching engineers?? how to do their job.

We can never know the circumstances and any answers could easily kill
YOU.

 

[Danny]

er.... I'm not quite sure what to make of this answer....as far as
being a 'real engineer'...i think i qualify...both by education,
qualification and experience. i have in fact been able to give quite a
lot of help on this group over about 7 years. and, yes i am well aware
of the dangers involved. i work for a big electric utility company and
we have very strict rules regarding safety AND a lot of experience in
HV testing. yes, i could simulate every possible
configuration...although with the nonlinearity of transformers it's not
trivial by any means. yes, i could do a cost/space/weight saving
exercise which would also be quite complex.....i could do a lot of
things actually....and whilst i am busy doing them (which i am) i just
thought someone out there might offer some advice based on the fact
that they might have gone through this process before. isn't that the
point of news groups.
and as for 'Wot's Your Real Problem?'.....what do you mean
exactly?.......and as far as the: 'This is a professional design
problem that has been addressed many times
by real engineers.' well, there is scant literature regarding this
topic. true the rectification circuits are well known but the
associated TUF's are not readily calculated when in use with a
reservoir capacitor. Terman quotes TUF's for rectifiers without
reservoir capacitors. i will be able to work them out myself although
it's not straight forward. i'd like to think that after being a member
of thes NG for some time now, both getting help and offering help that
i wouldn't get lectures on being a 'Real Engineer'.

many thx

Danny

 

[John G]

er.... I'm not quite sure what to make of this answer....as far as
being a 'real engineer'...i think i qualify...both by education,
qualification and experience. i have in fact been able to give quite a
lot of help on this group over about 7 years. and, yes i am well aware
of the dangers involved. i work for a big electric utility company and
we have very strict rules regarding safety AND a lot of experience in
HV testing. yes, i could simulate every possible
configuration...although with the nonlinearity of transformers it's
not
trivial by any means. yes, i could do a cost/space/weight saving
exercise which would also be quite complex.....i could do a lot of
things actually....and whilst i am busy doing them (which i am) i just
thought someone out there might offer some advice based on the fact
that they might have gone through this process before. isn't that the
point of news groups.
and as for 'Wot's Your Real Problem?'.....what do you mean
exactly?.......and as far as the: 'This is a professional design
problem that has been addressed many times
by real engineers.' well, there is scant literature regarding this
topic. true the rectification circuits are well known but the
associated TUF's are not readily calculated when in use with a
reservoir capacitor. Terman quotes TUF's for rectifiers without
reservoir capacitors. i will be able to work them out myself although
it's not straight forward. i'd like to think that after being a member
of thes NG for some time now, both getting help and offering help that
i wouldn't get lectures on being a 'Real Engineer'.

many thx

Danny

Danny, I don't want to upset anyone ,but often people come here with the
most ill defined problem and no evidence that what anyone says will be
used wisely.

Your problem is A. dangerous and B. quite extensive.

Yes, you may get some useful pointers here but surely a problem of this
nature is something that requires a team of experienced engineers who
have done it before and made all the mistakes.

There are numerous companies, for instance
http://www.phenixtech.com/products/index.php ,who do this kind of thing
all the time and don't need to have their head spinning with
possibilities (your words).

You will not be able to afford the equipment to calibrate your work so
you will get a more reliable outcome if you just accept that it is a job
for the specialists.

and as for 'Wot's Your Real Problem?'.....what do you mean

If you do not understand the sentence then ?
If you don't understand the implication then sorry.

And if you take it so seriously, you have not read this or other
electrical NGs very much.
I have been using that for a tag line since about 1985, yes in corporate
forums before BBSs or the Internet were born.

 

[Danny]

Danny, I don't want to upset anyone

and then promptly achieved what you didn't want to do....

http://www.phenixtech.com/products/index.php

yes i am well aware of phenix....we have bought a lot of gear from them
over the years as with heafly, hi-voltage, hipotronics, bicotest etc
etc.

for various reasons i want to build this one inhouse.

You will not be able to afford the equipment to calibrate your work

we can, and we do.

you will get a more reliable outcome if you just accept that it is a job

for the specialists

we've designed this particular test truck in-house before over the
years....and i'd like to do it again. specialist help is always
gratefully accepted. unfortunately no specialists on this group have
offered any yet. doesn't matter, as a 'real engineer' (i think) i'll
slog through the maths, get whatever expertise that i can get from long
term members of the section and continue.

And if you take it so seriously, you have not read this or other electrical NGs very much.

I have read and contributed to this NG quite a lot since about 1995 as
with alt.eng.electrical

I have been using that for a tag line since about 1985, yes in corporate

forums before BBSs or the Internet were born.

a 'tag line'...... 'corporate forums'.......oh I see now....the light
is shining in....extremely impressive. thanks for putting me right.