seeking stamford D range info

[brutus1955]

i am looking for information on the stamford D range alternator,

the unit i am looking at is in malaysia and i am here in the states, so getting hands on look is not possible

the unit is a 15kva single phase, what sets it apart is the
field poles are fixed in the housing, and the rotor is slotted
like an old dc generator but has slip rings instead of a commutator. slip rings of course needed to get ac power off the armature/rotor.

i have searched everywhere for the "D range" and no joy,

anyone here have any links or info on such an animal, i suspect that stamford quit the rather antiquated design in favor of a more tradition rotating field fixed stator brushed, then brushless design.

any help is appreciated.

bob g

http://www.microcogen.info

 

[brutus1955]

guys, i am looking for any info at all on this series of alternator or alternatively and reference material on
what is known as "revolving armature ac generators"

also any info on transformer controlled alternators, i think they refer to them as "current compounding transformer" field control, so some such.

anything would be helpful, a book, a link, ancient mythology,
folklore, anything...

thanks
bob gayle

http://www.microcogen.info

 

[dArsonval]

Found very brief reference scrolling to page 14 of the pdf file here:

http://www.powertechengines.com/NewageData/Parts-Section4.pdf

 

[brutus1955]

dArsonval

that was the only reference i could find too, to the D range
stamford.

one elusive bugger it is turned out to be.

bob g

http://www.microcogen.info

 

[waross]

I have worked on transformer controlled generators with both rotating fields and stationary fields.
The principle of operation as I understand it is thus:
A constant current transformer is used along with a trim resistor to energize the field (through a bridge rectifier). The resistor is set to provide the proper voltage at no load. One output phase of the generator is passed through a CT. The output of the CT is scaled and converted to a voltage through a second resistor. This resistor is set to provide the proper amount of boost to provide the proper output voltage at full load. I understand that typical voltage regulation may be about 3% to 5%.
I installed a new 500KVA set about 30 years ago which used this system. In addition there was an AVR added to increase improve the voltage regulation to about 1% or 2%.
The transformer excitation system gives good motor starting performance and the addition of an AVR improves the voltage regulation.
The transformer excited sets are a great solution for remote sites where both money and talent are scarce. A failed AVR is difficult if not impossible to repair in the field and then only by an electronic expert.
It is a lot easier in isolated areas to find someone who can check and change transformers, resistors and diodes. I consider these systems to be almost bullet proof.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[brutus1955]

Thank you Master Waross

that is explanation is a big help in filling in the missing
pieces to the puzzle

after much more digging i find this sort of control probably lost favor as electronic AVR's got better, cheaper and more dependable.

i can also see how the market for the older method would still be strong in 3rd world applications, or where brute strength is needed as is the case with smaller installations.

at 15kva it isn't like there is likely much protection, regulation available, desirable or even needed for the types of loads serviced out in the sticks.

probably voltage regulation within 5% is all that is needed
for anything likely encountered.

thanks again

bob g

http://www.microcogen.info