ST head voltage at slower speeds

[veggie]

I have an Iota DLS55 smart charger that can operate in a range from 47 to 63 hz.
(Voltage range of 108 to 132)

Can anyone tell me what the approx. output voltage on one of the 120v legs of an ST5 head would be if it were running at 47hz. or 1410 rpm ??

veggie

[mike90045]

I think you will have to measure that under load.   Or, I'll be doing the same in about 2 months.

[veggie]

I think you will have to measure that under load.   Or, I'll be doing the same in about 2 months.

The proposed load will be 13 amps @ 108 volts (Max.)

veggie

[veggie]

Here's the secs on the charger.
I am exploring the possibility of running the lister at a slower speed for battery charging and speed it up for 120/240 output in emergencies.
For my current sheave ratios, this would equate to:

Emergency power 60hz. = 650 rpm

Battery charging 47hz = 510 rpm

The question is whether the ST head will provide the minimum voltage of 108 VAC when running at 47 hz. ??

veggie

[BruceM]

With an AVR connected to the AC output, and not using the harmonic winding, you can have whatever voltage output you want. 

[veggie]

With an AVR connected to the AC output, and not using the harmonic winding, you can have whatever voltage output you want. 

And still get up to 13 amps ?

veggie

[BruceM]

Sure, at roughly 50Hz, your ST-5 should put out 13 amps of 120VAC without any trouble.  
In picking an AVR, make sure you pick one that is rated for 50/60Hz power; then you'll be good  regardless of speed of operation.  

[veggie]

Perhaps I should have phrased my question a bit better.

I am wondering if I could simply plug the Iota charger into the 120 outlet on my ST head and slow the engine down to 510 rpm (50 hz on the genney) and still produce enough juice to meet the minimum volts/hz. to satisfy the charger? (That being 108 volts at 47 hz.)

Removing the ST head and taking it apart is not an option for me.

veggie

[mobile_bob]

what ever you do, keep an eye out on the amperage of the field, try not to exceed the amp rating of the unit
as stated on the tag,

my understanding is some of the st heads are easily damaged in this regard.

intermittent/surge excursions to well over nameplate field rating is probably not going to be a problem, but long term battery
charging at significantly higher field current might be problematic, given the airflow is also reduced at lower rpm operation.

just something to keep in mind

fwiw/ymmv

about to post when i saw your clarification,
i don't think you will get 108volts at 47 hz, connect as a 60hz machine
perhaps you can bring out all the leads and with relays switch from 60 hz for full AC production, down to 50hz for 47hz
operation and stay above the needed 108vac
that is if your head is made with the extra set of wires to work as a 50hz as well as 60hz head

bob g

[BruceM]

It's unlikely to work, but you could test it carefully. I suspect the voltage might drop too much.

Another approach would be to bring out the generator wires to some switches so that the 50Hz winding selection could be made- that will boost the voltage for lower speed operation.

You presently are operating on the stock harmonic setup, right?

Bob- I have little concern about the field current or cooling  in this application since his low speed is essentially 50Hz, and most of the ST heads are designed for operation at 50 or 60Hz.  Anything much lower than 50Hz, and all bets are off.

[veggie]

BruceM, Bob

I am in awe with the stuff you guys know about circuits and power generation.

50HZ for would be 540 rpm engine speed.
Flipping a switch for the head (to 50hz. ) and sliding a lever to drop the engine speed would be ok for me.
Very interesting ?

veggie

[veggie]

With an AVR connected to the AC output, and not using the harmonic winding, you can have whatever voltage output you want.  

Ok, so lets move back to your original suggestion which may be the proper way to do it.

1] When you refer to "not using the harmonic winding", do you mean disconnecting it from it's current terminal, or simply not connecting it to the AVR ?

2] Sorry, but I am unfamiliar with ST wiring. Where does the harmonic winding reside within the head. ?

veggie

Edit: BTW, if this mod has already been done by some members, please jump in. (or direct me to the thread).

[BruceM]

Your ST should come with a printed manual that shows you the wiring choices to make for 120, 240V or 50/60 Hz.  The connections are in the "dog house".

When using an AVR without the harmonic winding, you disconnect the harmonic winding(2) wires  in the dog house and just cap them with wire nuts (or tape up the ends) for safety.  It's still there, just not connected to anything. The input of the AVR is the 120VAC output, and the output of the AVR goes to the bridge diode, for conversion to DC, and onward to brushes and the field coil of the rotor.  Some AVRs will take both the AC input, as well as rectified AC as an input. (Like the design I posted on this forum.)

An AVR is appealing in this 50/60 Hz arrangement, but I'm biased, I think the stock harmonic excitation regulation, AC waveform, and flicker are just too crappy, at least on my own ST-3.

Tom at Georgia Generators is selling AVRs for the ST-5 and told me he was going to create a wiring diagram for hooking them up to the 120VAC for excitation. There are no manuals or schematics for the products he sells, though they are cheap.  He has been selling them hooked up as series regulators of the harmonic output, which is pretty nuts, as it does nothing for improving flicker or cleaning up the AC waveform of the ST heads.  If you don't use the harmonic, the AC waveform on the ST heads looks quite good.  So instead of using the harmonic winding as a source for rotor excitation, I highly recommend using a small amount of your AC output (through an AVR) instead.

[veggie]

Thanks very much BruceM. That clears things up a bit.
This setup may be ideal for low speed bank charging and higher speed emergency power.
Thanks to John F. my ST5 came with the modified dog house and all wiring is arranged in a neat accessible way.

The goal then is 108vac (up to 120) at 48 hz. from an ST5 head which is wired for 60 HZ but running at 1440 rpm.

When house power is required, the AVR is turned up, and the engine speed is increased so the head spins at 1800 rpm.

Perhaps a dumb question, but is the AVR installed on the one leg that I intend to use, or on the 240vac wiring prior to splitting into two lower voltage legs?

Any suggestions on AVR's  
Preferably one with a dial and not a circuit board pot with a tiny screw driver adjusting slot.

veggie

[BruceM]

I didn't realize your ST5 was configured as 240VAC output.  That complicates things a bit.
Tom's AVRs can be wired to do 240VAC.  They take excitation off of one leg and regulate the voltage on one leg, the other tracks, sort of. It is impossible to regulate the two 120V legs separately- so I prefer to regulate the 240V and let the 120 vary. Using  a step down transformer of about 300watts (240-120V) to the AVR solves that problem. That's how I run my home made AVR, also. (My ST-3 is set up as 240V.) 

You can't run the 13A battery charger of of one 120V leg of an ST-5 without causing problems, as the ST heads don't like a load imbalance.  You'll need a step down transformer to make 120V from 40V.  These are often available on ebay.  I prefer the toroid types myself.

Alternately, you could have switches to reconfigure the generator wiring to 120v output, as well as 50Hz. (Thus requiring no new hardware but the switches and wiring changes.)