220v 15Kw ST generator head, voltage regulator ideas??

[James Lerch]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year.

While running some load tests I started probing around with an O-scope
and was surprised to see how noisy the output was. In addition I was
really surprised to see the voltage across the stator. (pictures of
the O-Scope display are on the Work Day 7 & 8 page on my web address
below)

I tested the rectifier and it seems ok. I also looked at the brushes
and slip rings, both of which appear fine.

I was wondering if anyone has any ideas on why it does this and what I
could do to clean it up? If I can measure the inductance of the
stator, would adding an appropriately sized capacitor help?

For reference, here's a schematic layout on the generator:
http://www.utterpower.com/Trouble.htm

BTW, the generator works as is, but when I run it thru the 200amp
transfer switch and power my residence, the voltage drops low enough
to trigger the APC SmartUPS 1400 into running on battery while the
HVAC is running. (Line voltage drops to 107vac @ 61hz at the computer
room outlet, while I get 111vac at the generator)

The manual for the generator head discusses ways to adjust the voltage
regulation if it is too high by adding a variable resistor to the
stator winding. However, it doesn't say what to do if the voltage
output is insufficient.

My first thought was to build a new voltage regulator from scratch and
include the voltage regulation into the ATmega 128 engine rpm governor
assist project. In the mean time, I wonder if I can do anything to
assist the current situation?

Thanks for your time.


Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[Paul]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year.

While running some load tests I started probing around with an O-scope
and was surprised to see how noisy the output was. In addition I was
really surprised to see the voltage across the stator. (pictures of
the O-Scope display are on the Work Day 7 & 8 page on my web address
below)

I tested the rectifier and it seems ok. I also looked at the brushes
and slip rings, both of which appear fine.

I was wondering if anyone has any ideas on why it does this and what I
could do to clean it up? If I can measure the inductance of the
stator, would adding an appropriately sized capacitor help?

For reference, here's a schematic layout on the generator:
http://www.utterpower.com/Trouble.htm

BTW, the generator works as is, but when I run it thru the 200amp
transfer switch and power my residence, the voltage drops low enough
to trigger the APC SmartUPS 1400 into running on battery while the
HVAC is running. (Line voltage drops to 107vac @ 61hz at the computer
room outlet, while I get 111vac at the generator)

The manual for the generator head discusses ways to adjust the voltage
regulation if it is too high by adding a variable resistor to the
stator winding. However, it doesn't say what to do if the voltage
output is insufficient.

My first thought was to build a new voltage regulator from scratch and
include the voltage regulation into the ATmega 128 engine rpm governor
assist project. In the mean time, I wonder if I can do anything to
assist the current situation?

Thanks for your time.

You should be able to lower the resistance (indicated in the schematic)
to boost the output voltage, but the generator may actually be designed
for 110 VAC (rather than 120), and it might not be able to be pushed
much higher.

A simple solution is a boost transformer, which is simply a 120 VAC to
12 VAC transformer on the output. For 10 KW you only need a 1 KW
transformer, something like 12 VAC at 80 amps. You might find one in an
old welder or battery charger.

Paul

 

[John Jardine.]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year.

[...]
The generator waveform is very good quality. Usually the cheaper the
alternator, the worse the waveform.
You can't do anything about the waveshape. It's 'engineered in', fixed by
the physical coil structure and mettalics used.
Measuring the motor inductance can be a futile excercise. Inductance varies
widely depending on rotor angular position and for a reasonable L-deg graph
has to measured with voltages and currents near to those in normal
operation.
Increase/reduction of output voltage can be by manual/auto adjustment of an
external power supply, feeding AC or DC to the control winding rectifier.
You'd only need a couple of amps at a few volts. Can allow 110V machines to
run below 90Vac or upto 150Vac. (4Amp 'Variacs' are handy for this)
These smaller alternators usually have noticable leakage inductance, so a
few uF of power factor compensation caps wouldn't go amiss.
john

 

[James Lerch]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year.

[...]
The generator waveform is very good quality. Usually the cheaper the
alternator, the worse the waveform.
You can't do anything about the waveshape. It's 'engineered in', fixed by
the physical coil structure and mettalics used.

Well, I noticed that the Stator voltage spikes seem to correspond to
the noise in the output waveform. Any idea why I see such strange
spikes when I put the O-Scope across the stator brushes (after the
voltage rectifier?)

Measuring the motor inductance can be a futile excercise.

Actually, I was thinking about measure the inductance of the
generator's stator winding. The hope being to help clean up the
output voltage of the generator

Increase/reduction of output voltage can be by manual/auto adjustment of an
external power supply, feeding AC or DC to the control winding rectifier.

True, currently the generator has a "Z" winding that feeds a simple
rectifier that provides power to the stator. The only way I could
increase the generator's output voltage would be to increase the
voltage of the "Z" winding. A small step up transformer could work I
guess.

My first hope was I could clean up the existing voltage regulation
'system' as I only need the generator to output another 10Vac (or
so)..

Thanks



Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[Ignoramus28437]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year.

[...]
The generator waveform is very good quality. Usually the cheaper the
alternator, the worse the waveform.
You can't do anything about the waveshape. It's 'engineered in', fixed by
the physical coil structure and mettalics used.

Well, I noticed that the Stator voltage spikes seem to correspond to
the noise in the output waveform. Any idea why I see such strange
spikes when I put the O-Scope across the stator brushes (after the
voltage rectifier?)

Can you put a suitable AC capacitor between 2 poles to inhibit these
spikes?

Actually, I was thinking about measure the inductance of the
generator's stator winding. The hope being to help clean up the
output voltage of the generator


True, currently the generator has a "Z" winding that feeds a simple

i

 

[Paul E. Schoen]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year.
[...]
The generator waveform is very good quality. Usually the cheaper the
alternator, the worse the waveform.
You can't do anything about the waveshape. It's 'engineered in', fixed
by
the physical coil structure and mettalics used.

Well, I noticed that the Stator voltage spikes seem to correspond to
the noise in the output waveform. Any idea why I see such strange
spikes when I put the O-Scope across the stator brushes (after the
voltage rectifier?)

Can you put a suitable AC capacitor between 2 poles to inhibit these
spikes?

Actually, I was thinking about measure the inductance of the
generator's stator winding. The hope being to help clean up the
output voltage of the generator


True, currently the generator has a "Z" winding that feeds a simple

i

I don't have much experience with generators, but I have some ideas:

(1) The stator voltage could be increased and smoothed by adding a
capacitor to the output of the bridge rectifier.

(2) The bridge rectifier may not be of the best quality, and may have some
problems not detected by an ordinary forward conduction tester. Replace it
with a high efficiency bridge with at least 600 V breakdown and 20 amps or
more. Probably less than $5.

(3) The 15 Hz modulation is probably due to insuffient flywheel effect, or
oscillation in your coupling bushing. If you removed or modified the
original flywheel/pulley, make sure your new one has at least as much
inertial mass.

(4) Your initial tests showed adequate voltage (243 V at 28 amps), but now
you report only 111 VAC with it connected to the house. It is important to
have a balnced load on both sides of the 240 VAC which is fed to the house.
If you have only one phase connected, or if there is greatly different load
on the two phases, you might get low voltage and distortion problems.

Paul

 

[Rich Grise]

Greetings All,

I built a 11.2Kw diesel generator from parts I purchased off Ebay last
year. ....
BTW, the generator works as is, but when I run it thru the 200amp
transfer switch and power my residence, the voltage drops low enough
to trigger the APC SmartUPS 1400 into running on battery while the
HVAC is running. (Line voltage drops to 107vac @ 61hz at the computer
room outlet, while I get 111vac at the generator)

Sounds like your generator is getting dragged down by your HVAC, and
the UPS is going into brownout.

Try not to run the air conditioner from your emergency power, maybe?

Good Luck!
Rich

 

[Tony Williams]

True, currently the generator has a "Z" winding that feeds a
simple rectifier that provides power to the stator. The only
way I could increase the generator's output voltage would be to
increase the voltage of the "Z" winding. A small step up
transformer could work I guess.

These low power alternators all seem to use
"harmonic excitation", which seems to be claimed
as having self-regulation in some way.

What is "harmonic excitation"?

My first hope was I could clean up the existing voltage regulation
'system' as I only need the generator to output another 10Vac (or
so)..

Is there any way to leave the main excitation loop
as it is and add-in a controlled amount of extra
field current, either from a crude closed-loop AVR,
or simply in proportion to the load current?

 

[James Lerch]

Can you put a suitable AC capacitor between 2 poles to inhibit these
spikes?

That's on my to do list, I just wasn't sure how the Z winding would
react, nor how much capcitance to put across the stator..


Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[Ignoramus4106]

That's on my to do list, I just wasn't sure how the Z winding would
react, nor how much capcitance to put across the stator..

I can give you a cap to try...

i

 

[James Lerch]

I don't have much experience with generators, but I have some ideas:

(1) The stator voltage could be increased and smoothed by adding a
capacitor to the output of the bridge rectifier.

Thought so, I'll throw a few mF across it as see what happens

(2) The bridge rectifier may not be of the best quality, and may have some
problems not detected by an ordinary forward conduction tester. Replace it
with a high efficiency bridge with at least 600 V breakdown and 20 amps or
more. Probably less than $5.

I actually have a few I salvaged out of a large SMPS, I'll give it a
try and see if anything changes.

(3) The 15 Hz modulation is probably due to insuffient flywheel effect, or
oscillation in your coupling bushing. If you removed or modified the
original flywheel/pulley, make sure your new one has at least as much
inertial mass.

Well, I built it from scratch, so it is what it is.. One crazy Idea I
had was to attempt to build an active voltage regulator, one that was
smart enough to compensate for the reduction in angular velocity
between power strokes. Sensing when to try and compensate for this,
and how much to compensate might be interesting

(4) Your initial tests showed adequate voltage (243 V at 28 amps), but now
you report only 111 VAC with it connected to the house. It is important to
have a balnced load on both sides of the 240 VAC which is fed to the house.
If you have only one phase connected, or if there is greatly different load
on the two phases, you might get low voltage and distortion problems.

Indeed, my load tests were into ideal loads (220v resistance heaters,
a pottery kiln). The load on the house is a different story. However,
Maybe adding some trim capacitors to the offensive inductive loads
will help... (When running off the grid, I've been lead to believe
residential customers don't' care about power factor, but when running
off the genset, is power factor something to consider?)

Thanks



Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[James Lerch]

These low power alternators all seem to use
"harmonic excitation", which seems to be claimed
as having self-regulation in some way.

What is "harmonic excitation"?

Damn fine question, one that google doesn't seem to want to help me
with

Not knowing how the system attempts to self regulate, I was (and am) a
little conerned with adding capacitance across the stator. Perhaps I
shoud incorporate a fuse into the stator power circuit before I start
screwing around with it...

Is there any way to leave the main excitation loop
as it is and add-in a controlled amount of extra
field current, either from a crude closed-loop AVR,
or simply in proportion to the load current?

Probably, I've got an AVR based development board I plan on
incorporating into the generator. The first job for this system will
be to monitor for critical events and shut the system down in case of
emergency. (low oil, high temp, etc). Once I get that part working,
the next goal was to develop an assist system to help the mechanical
govenor keep the engine RPM in check.

After all that's figured out, an active voltage regulator sounds like
an interesting project...


Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[James Lerch]

Sounds like your generator is getting dragged down by your HVAC, and
the UPS is going into brownout.

The diesel engine still has plenty of power left in it, and the engine
RPM is accurate under the load of the HVAC. It is just the crude self
regulation that isn't perfect. Considering how incredibly simple and
crude the system is, I find it amazing it works as well as it does.
If it wasn't for the UPS, I probably wouldn't even worry about it.

Try not to run the air conditioner from your emergency power, maybe?

If only it were so simple!! {shrug}

James
Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[James Lerch]

You should be able to lower the resistance (indicated in the schematic)
to boost the output voltage, but the generator may actually be designed
for 110 VAC (rather than 120), and it might not be able to be pushed
much higher.

Well, the variable resitor isn't included with the generator head when
purchased. It would only be added as an option if the voltage were to
HIGH...

I'm thinking that some Chinese company figured out that the generator
would run with out the resistor if "X" amount of copper windings were
removed. In doing so they saved the cost of the resistor and probably
several feet of copper wire..

I guess you get what you pay for, but honesty I'm pretty happy with it
so far (all things considered).

Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[James Lerch]

I can give you a cap to try...

Thanks Ig, but I probably have a few here

I have this real bad problem about refusing to throw away all the
scrap SMPS I replace at work. They seem to be full of "candy" for
tinkerig with electronic stuff. Heat sinks, fans, rectifiers,
mosfets, etc.... My Induction heater was made from mostly SMPS
parts!




Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction, Testing, and Coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 11.2Kw generator project)
Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
Calvin Coolidge

 

[Ignoramus4106]

I have this real bad problem about refusing to throw away all the
scrap SMPS I replace at work. They seem to be full of "candy" for
tinkerig with electronic stuff. Heat sinks, fans, rectifiers,
mosfets, etc.... My Induction heater was made from mostly SMPS
parts!

Yeah. I had a similar experience with UPSes. I made a phase converter
out of an old Ferrups UPS (with a beautiful enclosure, big sliding
tray etc).

http://igor.chudov.com/projects/17.5-Phase-Converter/

this phase converter is now my big workhorse.

i