Replacement generator head questions

[Fairmountvewe]

Hi all, and a happy snowy Sunday to those of us lucky enough to live in Central Ontario.  As the title implies, I am tentatively looking for a replacement generator head for my newly acquired LD1 (3.5 hp) generator.  I had the chance yesterday to do some playing, and the original head was putting out 108V AC and 9.5 V DC with a 1300 w heater connected to it.  Not really quite up to snuff as far as acceptable power specs for running capacitive loads, and certainly not enough to charge the 12V battery.  Now admittedly I know very little about the magical inner workings of a generator head, especially one with both AC and DC windings, (except not to let the magic smoke out), so I am wondering about re-powering it with a small (2 Kw) ST head, or do I just try and get this one updated or re-wound if that is possible?  What say ye?  Thanks.

Peter

[dieselgman]

First, what engine speed or frequency were the readings taken at? If it was not running up to speed then the voltages would all be low and you will need to adjust governor to get it to rated speed before tossing out the baby with the bath water! We can discuss other low-voltage issues after this important determination.

dieselgman

[Bottleveg]

I’d be inclined to wire it to the diagram that Mick put up. Then set the engine to 60hz. I’m presuming you need 110v 60hz? What frequency does the genny plate give?
I think the LD1 is 1500rpm/ 50hz and 1800rpm/ 60hz?
Then adjust the shunt field resister to 110v, off load, and the auxiliary field resister to as close to 110v as you can get on load. I’m not sure how well the LD engines regulate.
I think the settings for the 12v charge resister are 13.5 Low and 15.5 Hi setting.
1.5kva will give you 1200w constant and a bit more when needed.
If the engine is 3.5hp @ 1800rpm it will only produce 1500rpm on the constant rating so I’d be inclined to keep the British built genny with self starting.
   Mark.

[Fairmountvewe]

GMan;

I am presuming 1800 rpm, as there is no adjustable idle that I can see.  Just run and fuel off.  The plate says the LD1 will put out 110 v @61 Hz unloaded, but, under 1300 w resistive load, it was down to 108/59 as previously said.  I thought that North American standard was 120V, +/_ 5% and that anything within 5% (114-126 V AC) was okay.  108 v AC is 10% less than the optimum 120.  Am I wrong here? 

Mark;

I have to re-read Mick's information, and get up the guts to start playing with big-assed hand wound resistors, but I am a little confused about your last statement....
"If the engine is 3.5hp @ 1800rpm it will only produce 1500rpm on the constant rating" Are you saying the engine speed drops 300 rpm under load? 

So much to learn.  Now if only work, farming and those pesky family obligations would quit getting in the way of my hobbies.......

[dieselgman]

There is a speeder spring adjustment to change your operating speed... this must be achieved before any of the other adjustments are attempted. 1500 rpm is correct for European 50 Hz and 1800 rpm is correct for North American 60Hz.

dieselgman

[Bottleveg]

Mark;

I have to re-read Mick's information, and get up the guts to start playing with big-assed hand wound resistors, but I am a little confused about your last statement....
"If the engine is 3.5hp @ 1800rpm it will only produce 1500rpm on the constant rating" Are you saying the engine speed drops 300 rpm under load? 

Sorry, that’s a typo. It should read 1500 watts. You may well get it drop in revs/HZ when the engine is under load, it depends how well it regulates.
As Dieselman says, set the rpm before any other adjustment. You may find that the off-load rpm needs to be increased later if a full load drops the voltage too much.
    Mark. 

[Fairmountvewe]

I am not sure I have to do too much adjustment to the rpm as the unloaded generator is running right in at 61.3 Hz  Thats okay.  It is the lower voltage that has me concerned.  Like I said earlier, I thought 120 V was the N.A. standard, and this puts out 110-ish (less if under load).  That is fine for a purely resistive load, but as soon as a motor gets involved (think sump pump or furnace fan), I am wondering if I shouldn't have more volts. 

[Bottleveg]

I am not sure I have to do too much adjustment to the rpm as the unloaded generator is running right in at 61.3 Hz  Thats okay.  It is the lower voltage that has me concerned.  Like I said earlier, I thought 120 V was the N.A. standard, and this puts out 110-ish (less if under load).  That is fine for a purely resistive load, but as soon as a motor gets involved (think sump pump or furnace fan), I am wondering if I shouldn't have more volts. 

You should be able to adjust the voltage up to 120v with the SFR, when it’s wired correctly. You may need to put it up to 125v no-load if the voltage drops too much on-load. Adjust the AFR for on-load voltage. This should be behind the genny end cover.
Starting a motor could be a problem, it depends what size motor, but this would be true of any generator you fitted. The output of the engine will be the limiting factor, even if you fit a larger genny.
   Mark.

[listeroil]

Peter

It is no big deal to adjust the big resistor. Just do it when the engine is switched off. Move it about a 1/4 inch one way or the other and restart the generator it will either go up in voltage or down in voltage. From this information you will be able to work out which way to set it to increase the voltage to what you require.  Exactly the same procedure for the battery charging side as well.

As far as inductive loads motors battery chargers etc are concerned Listers suggest fitting capacitors to correct the power factor. I can say from first hand experiance that they work very well. Heres a page from a lister manual that tells you what to do.






Mick