SOLA Constant Voltage Transformer

D

dre

Guest
Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Thanks

Andrew
 
dre wrote:

Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Thanks

Andrew

Try loading it with a light bulb.
Click to expand...

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
 
"dre" <dre7@sbcglobal.net> wrote in message
news:1168487645.556391.135450@i56g2000hsf.googlegroups.com...

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.
Click to expand...
How are you measuring the voltage?









--
 
dre wrote:
Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Thanks

Andrew
Click to expand...

It is not a sine wave output, which causes inaccurate readings with a
typical meter. You need a "True RMS volt meter" to read the actual
voltage.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
In article <1168487645.556391.135450@i56g2000hsf.googlegroups.com>,
"dre" <dre7@sbcglobal.net> wrote:

Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.
Click to expand...
Most constant-voltage transformers output a semi-square wave (sort of a
sinusoid with the tops flattened). It will not measure "properly" with
most voltmeters.

Isaac
 
"isw" <isw@witzend.com> wrote in message
news:isw-8CCD33.22483710012007@newsgroups.comcast.net...
In article <1168487645.556391.135450@i56g2000hsf.googlegroups.com>,
"dre" <dre7@sbcglobal.net> wrote:

Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Most constant-voltage transformers output a semi-square wave (sort of a
sinusoid with the tops flattened). It will not measure "properly" with
most voltmeters.

Isaac
Click to expand...
I don't understand why a ferroresonant transformer / capacitor combination,
should output anything other than a sine wave. Many years ago, I worked for
a company which made use of these devices to feed radio relay equipment, and
as far as I recall, they just had a normal sinewave output. I had a quick
look on the 'net at some Sola ones, and there is nothing in the specs to
suggest other than a sinewave output. It does, however, state that the
output voltage can be have a variance of +10 to -20% of the nominal rating
plate value. For the OP's example, that is potentially nearly 12v high worst
case, which added to the 118, gets pretty damn close to the 130 odd that he
is measuring. I wouldn't have expected his scanner to be that fussed about
this sort of level of overvolts anyway. Depends to some extent on the type
of power supply it uses. Also, as someone else suggested, loading the CVT
will probably bring the voltage down a little, although it wouldn't be a
very good CV source, if it dropped too far ...

Arfa
 
Arfa Daily wrote:
"isw" <isw@witzend.com> wrote in message
news:isw-8CCD33.22483710012007@newsgroups.comcast.net...
In article <1168487645.556391.135450@i56g2000hsf.googlegroups.com>,
"dre" <dre7@sbcglobal.net> wrote:

Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Most constant-voltage transformers output a semi-square wave (sort of a
sinusoid with the tops flattened). It will not measure "properly" with
most voltmeters.

Isaac

I don't understand why a ferroresonant transformer / capacitor combination,
should output anything other than a sine wave. Many years ago, I worked for
a company which made use of these devices to feed radio relay equipment, and
as far as I recall, they just had a normal sinewave output. I had a quick
look on the 'net at some Sola ones, and there is nothing in the specs to
suggest other than a sinewave output. It does, however, state that the
output voltage can be have a variance of +10 to -20% of the nominal rating
plate value. For the OP's example, that is potentially nearly 12v high worst
case, which added to the 118, gets pretty damn close to the 130 odd that he
is measuring. I wouldn't have expected his scanner to be that fussed about
this sort of level of overvolts anyway. Depends to some extent on the type
of power supply it uses. Also, as someone else suggested, loading the CVT
will probably bring the voltage down a little, although it wouldn't be a
very good CV source, if it dropped too far ...

Arfa
Click to expand...

Some of the SOLA units do produce a slightly squared wave. The
higher the line voltage, the more the sinewave is flat topped. They
also built motorized low distortion regulators that adjusted the line
voltage in 1/10 volt steps. I had one at a military TV station in the
early '70s. It would add or subtract 20 volts to the line, but the small
power grid in that area was so bad that I saw the line voltage drop to
90 volts, and shot up to 210 volts AFTER the regulator one day when some
idiot tried to switch the wrong generators to and from the grid. Some
of the small towns didn't bother to call the other stations, and weren't
very good with the manual controls that were still in use.


http://www.solaheviduty.com/support/faq.html


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:45A653E4.11668678@earthlink.net...
Arfa Daily wrote:

"isw" <isw@witzend.com> wrote in message
news:isw-8CCD33.22483710012007@newsgroups.comcast.net...
In article <1168487645.556391.135450@i56g2000hsf.googlegroups.com>,
"dre" <dre7@sbcglobal.net> wrote:

Hi:

New poster here, just wondering if anyuone can help me with this
beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Most constant-voltage transformers output a semi-square wave (sort of a
sinusoid with the tops flattened). It will not measure "properly" with
most voltmeters.

Isaac

I don't understand why a ferroresonant transformer / capacitor
combination,
should output anything other than a sine wave. Many years ago, I worked
for
a company which made use of these devices to feed radio relay equipment,
and
as far as I recall, they just had a normal sinewave output. I had a quick
look on the 'net at some Sola ones, and there is nothing in the specs to
suggest other than a sinewave output. It does, however, state that the
output voltage can be have a variance of +10 to -20% of the nominal
rating
plate value. For the OP's example, that is potentially nearly 12v high
worst
case, which added to the 118, gets pretty damn close to the 130 odd that
he
is measuring. I wouldn't have expected his scanner to be that fussed
about
this sort of level of overvolts anyway. Depends to some extent on the
type
of power supply it uses. Also, as someone else suggested, loading the CVT
will probably bring the voltage down a little, although it wouldn't be a
very good CV source, if it dropped too far ...

Arfa


Some of the SOLA units do produce a slightly squared wave. The
higher the line voltage, the more the sinewave is flat topped. They
also built motorized low distortion regulators that adjusted the line
voltage in 1/10 volt steps. I had one at a military TV station in the
early '70s. It would add or subtract 20 volts to the line, but the small
power grid in that area was so bad that I saw the line voltage drop to
90 volts, and shot up to 210 volts AFTER the regulator one day when some
idiot tried to switch the wrong generators to and from the grid. Some
of the small towns didn't bother to call the other stations, and weren't
very good with the manual controls that were still in use.


http://www.solaheviduty.com/support/faq.html
Click to expand...
So what's the reasoning behind it then, Michael ? Is it that the core
actually saturates to square off the top of the wave ?

Arfa
 
Arfa Daily wrote:
So what's the reasoning behind it then, Michael ? Is it that the core
actually saturates to square off the top of the wave ?
Click to expand...

Yes, and some items are designed to only be powered form these
transformers. CATV line amplifiers are typically line powered though the
hardline coax by a 60 VAC 15 Amp CVT power supply, which was perfect
when the early square wave UPS systems came out. The 15 amps is fed from
somewhere near the center of a span, with roughly 50% in each
direction. The power supply modules had warnings not to use a sine wave
source for bench testing. I've worked with Sylvania/Texscan, Jerrold,
Vikoa, and IEE/RCA systems. They all used this system, but the older
equipment was 30 VAC at 30 amps.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:45A67ABB.3903CEB@earthlink.net...
Arfa Daily wrote:

So what's the reasoning behind it then, Michael ? Is it that the core
actually saturates to square off the top of the wave ?


Yes, and some items are designed to only be powered form these
transformers. CATV line amplifiers are typically line powered though the
hardline coax by a 60 VAC 15 Amp CVT power supply, which was perfect
when the early square wave UPS systems came out. The 15 amps is fed from
somewhere near the center of a span, with roughly 50% in each
direction. The power supply modules had warnings not to use a sine wave
source for bench testing. I've worked with Sylvania/Texscan, Jerrold,
Vikoa, and IEE/RCA systems. They all used this system, but the older
equipment was 30 VAC at 30 amps.
Click to expand...

Thanks for that Michael. Very interesting.

Arfa
 
Arfa Daily wrote:
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:45A67ABB.3903CEB@earthlink.net...
Arfa Daily wrote:

So what's the reasoning behind it then, Michael ? Is it that the core
actually saturates to square off the top of the wave ?


Yes, and some items are designed to only be powered form these
transformers. CATV line amplifiers are typically line powered though the
hardline coax by a 60 VAC 15 Amp CVT power supply, which was perfect
when the early square wave UPS systems came out. The 15 amps is fed from
somewhere near the center of a span, with roughly 50% in each
direction. The power supply modules had warnings not to use a sine wave
source for bench testing. I've worked with Sylvania/Texscan, Jerrold,
Vikoa, and IEE/RCA systems. They all used this system, but the older
equipment was 30 VAC at 30 amps.


Thanks for that Michael. Very interesting.

Arfa
Click to expand...

You're very welcome. I like it that some people on these groups
actually want to learn more about electronics. I've been studying every
aspect of it that I could for over 40 years. The more you know about
it, the easier it is to fill in the gaps. :)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
dre wrote:
Hi:

New poster here, just wondering if anyuone can help me with this
beast. I'm sort of hoping to use it as an isolation transformer for
my scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Thanks

Andrew
Click to expand...
some of the units that i have owned have a large capacitor as part of the
assembly. if your unit has one check that the capacitor has not failed or
changed value.
 
TimPerry wrote:
dre wrote:

Hi:

New poster here, just wondering if anyuone can help me with this
beast. I'm sort of hoping to use it as an isolation transformer for
my scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Thanks

Andrew


some of the units that i have owned have a large capacitor as part of the
assembly. if your unit has one check that the capacitor has not failed or
changed value.


Wouldn't it have been easier to just say "yes" since he specifically
Click to expand...
asked whether it could be the capacitor?

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
 
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in news:iwtph.9259$KQ2.5350
@newsfe6-win.ntli.net:

So what's the reasoning behind it then, Michael ? Is it that the core
actually saturates to square off the top of the wave ?
Click to expand...
Some Googling turned up more info about constant-voltage transformers.

It is indeed saturation of the core that provides the "constant voltage"
feature. (If the input voltage goes up, and the core is already in
saturation, the output voltage won't change.)

For this reason, early CVTs had a non-sinusoidal output.

However, modern CVTs can be bought with "low-harmonic" output, meaning
it's a sine wave without any harmonics. This is achieved by a third
winding on the core, connected to a capacitor to resonate at the power-
line frequency. (It acts like a tank circuit, picking out the
fundamental frequency and discarding the harmonics.)

Now, if the winding/capacitor resonant frequency differs from the line
frequency, the CVT can't be expected to deliver its specs.

1. Buy a 60Hz CVT and connect it to 50Hz, don't expect it to work.

2. Connect a CVT to a gas-engine alternator (poor frequency control)
don't expect it to work.

3. Capacitor changes value or open-circuits, don't expect it to work.

Bottom line: Depending on the age and design of the CVT, it may or may
not have sine wave output.

P.S. In any case, the core saturates every cycle, so expect the
transformer to get hot (hysteresis loss).
 
Jim Land wrote:
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in news:iwtph.9259$KQ2.5350
@newsfe6-win.ntli.net:


So what's the reasoning behind it then, Michael ? Is it that the core
actually saturates to square off the top of the wave ?



Some Googling turned up more info about constant-voltage transformers.

It is indeed saturation of the core that provides the "constant voltage"
feature. (If the input voltage goes up, and the core is already in
saturation, the output voltage won't change.)

For this reason, early CVTs had a non-sinusoidal output.

However, modern CVTs can be bought with "low-harmonic" output, meaning
it's a sine wave without any harmonics. This is achieved by a third
winding on the core, connected to a capacitor to resonate at the power-
line frequency. (It acts like a tank circuit, picking out the
fundamental frequency and discarding the harmonics.)

Now, if the winding/capacitor resonant frequency differs from the line
frequency, the CVT can't be expected to deliver its specs.

1. Buy a 60Hz CVT and connect it to 50Hz, don't expect it to work.

2. Connect a CVT to a gas-engine alternator (poor frequency control)
don't expect it to work.

3. Capacitor changes value or open-circuits, don't expect it to work.

Bottom line: Depending on the age and design of the CVT, it may or may
not have sine wave output.

P.S. In any case, the core saturates every cycle, so expect the
transformer to get hot (hysteresis loss).
Click to expand...

I've found a generator to have pretty decent frequency control, the one
I borrowed during a recent lengthy outage measured anywhere between
58-60 Hz depending on load. Would 2Hz really be enough to mess up the
performance of a CVT?
 
James Sweet <jamessweet@hotmail.com> wrote in news:F0Wph.995$q32.463
@trndny01:

I've found a generator to have pretty decent frequency control, the one
I borrowed during a recent lengthy outage measured anywhere between
58-60 Hz depending on load. Would 2Hz really be enough to mess up the
performance of a CVT?
Click to expand...
Just looking through Sola's site, I saw one of their CVTs rated 57-63 Hz,
so I would expect a CVT would probably work OK with the generator you
tested. Do they all hold frequency that well?
 
Jim Land wrote:
James Sweet <jamessweet@hotmail.com> wrote in news:F0Wph.995$q32.463
@trndny01:


I've found a generator to have pretty decent frequency control, the one
I borrowed during a recent lengthy outage measured anywhere between
58-60 Hz depending on load. Would 2Hz really be enough to mess up the
performance of a CVT?



Just looking through Sola's site, I saw one of their CVTs rated 57-63 Hz,
so I would expect a CVT would probably work OK with the generator you
tested. Do they all hold frequency that well?
Click to expand...

Heck if I know, that's the only one I've ever used. I'd imagine it
depends on how much horsepower overhead the motor has and the condition
and adjustment of the governor. The throttle response of the carburetor
would be an important factor as well. I'm curious how much the output
would be affected as the frequency drifted.
 
CJT wrote:
TimPerry wrote:
dre wrote:

Hi:

New poster here, just wondering if anyuone can help me with this
beast. I'm sort of hoping to use it as an isolation transformer for
my scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts
with line voltage in. The plate states secondary voltage is 118,
so what's causing the overage? Do I not have it loaded enough
(rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Thanks

Andrew


some of the units that i have owned have a large capacitor as part
of the assembly. if your unit has one check that the capacitor has
not failed or changed value.


Wouldn't it have been easier to just say "yes" since he specifically
asked whether it could be the capacitor?
Click to expand...
come to think of it, it could be the capacitor.

here are some schematics for those that are interested
http://www.solaheviduty.com/products/powerconditioning/cvs.htm
 
Jim Land wrote:
James Sweet <jamessweet@hotmail.com> wrote in news:MnYph.603$Ch1.153
@trndny04:


I'm curious how much the output
would be affected as the frequency drifted.



According to Sola's PDF for its CVS series of constant-voltage
transformers,
http://www.solaheviduty.com/products/powerconditioning/pdfs/opchars.pdf

you can expect the output voltage to rise about 1.5% for each 1% rise in
the frequency. So, freq goes up 1Hz, 1/60 = 1.7% x 1.5 = 2.5% x 120V =
3V rise.

This is true for their CVS series transformers---with other models, YMMV.
Click to expand...

Hmm, they say the efficiency is up to 92% full load, makes me wonder
what it is on average at more typical load. Sounds like those things
burn up a lot of extra juice.
 
James Sweet <jamessweet@hotmail.com> wrote in news:lvYqh.8591$Wz.2996
@trndny06:

Hmm, they say the efficiency is up to 92% full load, makes me wonder
what it is on average at more typical load. Sounds like those things
burn up a lot of extra juice.
Click to expand...
As noted above, the core saturates every half-cycle, so there are big core
losses due to hysteresis. These transformers are notorious for running
hot. Hence, reduced efficiency.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top