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Author Topic: How to Choose a Gen Head  (Read 497 times)

Kishore

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How to Choose a Gen Head
« on: July 09, 2021, 07:35:04 AM »
Hi Everyone - my first post, so many thanks for allowing me into the forum. ~I'm completely new to the world of lister engines, but we have recently moved "off grid" so a lister generator to provide 230VAC seems like a good idea.

I recently acquired an Lr1, but I'm thinking of maybe trying to source and sr2 as well. What I'm struggling to work out is how to couple the engine to the generator head - I've read that lister flywheels are not of a standard SAE size, so I can work out which generator head would fit?

As I understand it, many people link the engine and the gen head with a drive belt.....if possible I'd like to couple the two together directly, via the bell housing  like the original generator heads were coupled to the engines.

I know that there are still lots of the contemporary gen heads/alternators around, but I don't think that I have the expertise to rewind/repair one (and again, as I understand it, it's more often the genhead/alternator that goes wrong then the engine

is it possible to source a modern AVR genset that can be coupled direct to the engine via the bell housing? - I have seen some adaptors on stationaryengineparts.com but can't seem too find out the SAE size of the SR2's flywheel

also what size genset should I be looking to pair up with the Lr1/SR2? 

I'm very grateful for all and any help that you can offer - they may seem very basic questions but I can't deem to find the info anywhere on the web, and I'd love to get my foot in the doo in the lister world! :)

mihit

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Re: How to Choose a Gen Head
« Reply #1 on: July 09, 2021, 08:02:10 AM »
Welcome. 230VAC, you must be in the developed world?

Foremost my recomendation is to not double-convert energy. If you're running a diesel engine, to run a generator, to run an electric motor - that is wasteful. Where you can, try and drive off your prime mover, obviously this isn't so applicable with domestic fridges and such, but is something to keep in mind.

I'm always in favour of de-coupling, either by belt, clutch or  cush-drive... Less stress on the crank and starting.

Anything is possible to fabricobble together, given the time, money and ingenuity. so if you want to direct-drive that's always an option.

LR1 is about 5HP so you're realistically going to drive a 3kW head. Enough for a sensible "small home"
The SR2 will do about 11kW. Enough for the home, and the workshop :D

Kishore

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Re: How to Choose a Gen Head
« Reply #2 on: July 09, 2021, 08:17:38 AM »
thanks mihit - yes we are in the Uk, hence 230 VAC

what you say about double converting energy makes sense - however, ideally I'd like to pour a concrete base and build a shed around the engine just to try and keep the noise down, it going to be easier to keep the engine "isolated"

one of my reasons for wanting to stay direct drive was just for the simplicity and "compactness", also, even if I could weld, living off grid makes it difficult to get power to weld! so I'd like to avoid having to make a frame to mount pulls and belts etc

thanks for the info on sizing the gen head

CS Dave

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Re: How to Choose a Gen Head
« Reply #3 on: July 18, 2021, 11:39:07 AM »
It may be worth you googling the difference between kVA and kW

If you do know your kVA and your kW output you can calculate a precise Power Factor by dividing the kW by the kVA. The formula for converting kVA into kW is: Apparent power (kVA) x power factor (pf) = actual power (kW) The formula for converting kW into kVA is: Actual power (kW) / power factor (pf) = apparent power (kVA)

Diesel Generators generally have a power factor of 0.8.

So my CS 8/1 Start-o-matic has a 4.5 kVA head so it produces 3.6 kW from 8HP - will run our house comfortably
1945 Lister CS 5/1 driving a sawbench
1963 Lister CS 8/1 Startomatic  4.5 KVA

sirpedrosa

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Re: How to Choose a Gen Head
« Reply #4 on: July 18, 2021, 03:59:06 PM »
Hi Gentles

As far as I know that power factor is relatively to the magnetic and heat losses. Wont you all agree?

BR
VP
By order of firing up:
Bernard 18A - 1968 (mama's water pump - year of my birth)
Petter PAZ1 - Jun 1967, 3HP, sn 416xxxx
Petter PAZ1 - Nov 1979, 3HP, sn 425xxxx
Lister 12/2 - 12651227, the pearl!

mike90045

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Re: How to Choose a Gen Head
« Reply #5 on: July 18, 2021, 11:07:03 PM »
Hi Gentles

As far as I know that power factor is relatively to the magnetic and heat losses. Wont you all agree?

BR
VP


Power Factor is related to the offset between the phase of the voltage and the phase of the amps of the load.
It is caused by Inductance and Capacitance in the loads.

https://en.wikipedia.org/wiki/Power_factor

 ( excerpt) Lagging and leading power factors
Power factor is described as leading if the current waveform is advanced in phase with respect to voltage, or lagging when the current waveform is behind the voltage waveform. A lagging power factor signifies that the load is inductive, as the load will “consume” reactive power. The reactive component Q {\displaystyle Q} Q is positive as reactive power travels through the circuit and is “consumed” by the inductive load. A leading power factor signifies that the load is capacitive, as the load “supplies” reactive power, and therefore the reactive component Q {\displaystyle Q} Q is negative as reactive power is being supplied to the circuit.

BruceM

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Re: How to Choose a Gen Head
« Reply #6 on: July 23, 2021, 05:36:39 AM »
As far as practical generator head use goes, a very bad power factor load looks to the generator head (stator) wiring as a larger load, so it makes sense to oversize the generator head if using such things as a poor power factor battery charger.  The extra reactive power will only show up slightly in the fuel consumption.  Another matter is that many AVR's that are not true RMS reguators may not respond well to bad power factor load, which tend to flatten the top of the sine.  The voltage may then be high or low enough to cause problems.  It's something to watch with a true RMS meter if trying some new gear.

It's different matter for inverters, which see reactive power as a real load that is not only additive for inverter capacity, but also additive for battery draw.

Switch mode power supplies, such as electronic welders and battery chargers that are not power factor corrected will have large capacitors after the bridge diode from the AC mains.  Ditto for large linear supplies that don't use a large "critical value" inductor before the bulk capacitors. These big capacitors are the cause of bad power factor; when the rectified mains voltage rises above the bulk DC level in the capacitors, there's a big increase in current; the capacitors look like nearly a dead short.  It tends to saw off the top of the mains sine.  The modern electronic solution is to instead use a buck/boost converter to regulate the mains current draw to match it's sine voltage swing throughout the sine.  The old fashioned way was to use a large power inductor to smooth the current draw from the mains, with a value above the "critical inductance".  Today no one wants the weight, size and cost of a large mains filter inductor, thus the use of the high speed buck/boost power factor correcting designs, despite the extra complexity.

Induction motor loads also affect power factor but are lagging instead of leading like a capacitor.  The current waveform is delayed relative to the sine voltage.  This will again add to the wiring load on the generator head (stator) but only slightly to fuel use.  Again, inverters will see this as additive to the normal load, so it is wise to add enough capacitance to correct the PF, to minimize the battery current draw for your regular motor loads. Adding motor run capacitance until inverter DC power is at a minimum will do the trick.

That's my 2 cents worth on practical generator and inverter power factor issues.




mihit

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Re: How to Choose a Gen Head
« Reply #7 on: July 25, 2021, 12:07:49 AM »
thanks mihit - yes we are in the Uk, hence 230 VAC

what you say about double converting energy makes sense - however, ideally I'd like to pour a concrete base and build a shed around the engine just to try and keep the noise down, it going to be easier to keep the engine "isolated"

one of my reasons for wanting to stay direct drive was just for the simplicity and "compactness", also, even if I could weld, living off grid makes it difficult to get power to weld! so I'd like to avoid having to make a frame to mount pulls and belts etc

thanks for the info on sizing the gen head

Fair point and obviously you know what's going to work best for you. Keep us updated and post pics if you can, we always like pics :)

olNick

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Re: How to Choose a Gen Head
« Reply #8 on: August 04, 2021, 09:57:00 AM »
Hi,

I also am a proponent of decoupling, usually with belts.
When living off-grid, simplicity and readily/locally available options should take priority in preparation for the eventual failure.

Belts last a long time when applied correctly. Belt/pulleys are the most common power transmission mechanisms, available everywhere.

Let's say the alternator shits. It would be alot easier to source a locally available head and buy a new, or retrofit existing pulley to the new head, and be up and running within hours/day, versus ordering and waiting for a new, directly couple genhead; assuming you can find one to your non-standard flange.

Also, with a belt drive, you can "fine tune" your prime mover rpm; e.g you run prime mover at the rpm yielding the lowest BSFC which many times is also at the peak torque rpm, a good thing for transient response.

This works when the power requirements are available at this rpm.

regards,
nick
« Last Edit: August 04, 2021, 10:00:37 AM by olNick »

olNick

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Re: How to Choose a Gen Head
« Reply #9 on: August 04, 2021, 10:05:51 AM »
"also what size genset should I be looking to pair up with the Lr1/SR2? "

Please be aware that diesels like to run "loaded", otherwize they glaze rings, smoke, spit etc. when run unloaded.

Question would be "do I have enough load for a 12HP app. diesel engine?
Gen wize this would translate to about 25-35 Amps at 230V

regards,