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Author Topic: Lister H/A2 under volting  (Read 17579 times)
listernut
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« on: November 19, 2015, 03:35:01 PM »

Hello to All

Help needed with much appreciation on my Lister HA2 x 10 kva x1500 rpm 240volt ac genny.

This set is to provide backup to our intended of grid journey. It is ex police standby set that was housed in a permanent damp proof building since 1962 and has maintenance hrs. only together with v.tidy cosmetic and mechanical condition. It is key start using the 24volt dc windings and is an instant starter and all that.
The control boxes are very clean and rust free, likewise the contents show no corrosion. Continuity is good on all leads and connections clean and tight.
The problem facing me is that it producing low volts ac. The rpm is 1527 with 50.8 hz with 220v on no load. At 8kva load the volts drop to 200v and rpm to 1510.
No brushes sticking and all have good lengths outside the holders. slip rings are clean and without scores or damage. Spring pressure seems crisp and smooth.
We are getting 40volts short of the rated output which is 240volts ac. The only fault the is evident to me is that the voltage trimmer is ineffective but does show a resistance of 0.00-3.78ohms when rotated under "test" .

Does any have ideas that can help please?Huh


Any pointers to knowledge, skills, repairers, parts etc most welcome.
 
Deryk.
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roys
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« Reply #1 on: November 19, 2015, 03:52:20 PM »

Think Paul will be your man for Listers and will hopefully be along just shortly.

To me it sounds like it may have lost its residual magnetism, happens when an alternator has not been ran for a while, to re-energise you need to "flash" the windings by very briefly using a set of jump leads and a car battery and connecting them to the field windings in the correct polarity.
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Iain
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« Reply #2 on: November 19, 2015, 07:08:31 PM »

Hi
Is the voltage being checked with the meter on the generator or a separate meter?
If it is the on board voltmeter would be worth checking with a separate voltmeter/test meter, just to prove the generator meter is reading correctly, if not already done.

Iain
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listernut
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« Reply #3 on: November 20, 2015, 04:34:49 PM »

Hi Roy,  Thanks for your tip which prompts me into this oversight. As yet I cant i.d. the field windings req. for the flashing process due to there not being a connection panel with the xx or x cons to flash. Will study wiring in more detail tomorrow to see if I can fathom it...thanks again, deryk.

Hi Iain, Thank you also for your response re measuring values. The measurements taken were obtained with quality hand held meters. None of which has been calibrated recently though. The figures quoted were averaged from the three meters which were only hundredths apart so accepted by myself as close enough, I hope!!
Thank you also for  response ......deryk.
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oliver90owner
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« Reply #4 on: November 20, 2015, 07:23:58 PM »

Is the generator load rated in kW as well as kVA?  What was the power factor of your 8kVA load?  Single or three phase?

That engine is rated at 22HP@1800rpm.  It will be somewhat less at 1500rpm.  Perhaps15-20% less?

Details of the generator are needed, as is the engine data for that speed.  Residual magnetism usually only affects initial excitation, the generator then being self exciting although that might be a separate item.

I would think there is likely a large potentiometer which needs adjusting for 'coarse' no-load volts.  Apart from that I would say it is running fine.
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Justme
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« Reply #5 on: November 20, 2015, 08:31:41 PM »


To me it sounds like it may have lost its residual magnetism,

I doubt it.

That would result in no out put at all.

22hp is about 16kw.

I would hazard a guess that the electrics will be about 50% efficient.

So 8kw looks like the max you could get.

As mentioned is the rating in kVa & not Kw?

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roys
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« Reply #6 on: November 20, 2015, 09:04:49 PM »

Yip my mistake, I sped read the initial post thought he was getting next to no voltage out, didn't realise he was getting 200 V output.
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listernut
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« Reply #7 on: November 25, 2015, 11:21:11 AM »

Hello  oliver90owner,

Thanks for your reply on the HA/2. Here is some fuller info. Hope it helps you help me. Thanks, Deryk

This unit is in original spec.

The engine details: Type HA/2
                             Serial, 3030HA2212
                             BHP,    19
                             Rpm,    1500
                             Yr,        1962

Alternator details:   RA Lister
                             Type,   Left blank on I,d, plate.  No doubt supplied as a Lister unit, but may have been made by " Mawdsley" with whom they inter traded, or so I am told....
                             Serial,   20728/5
                             KVA,     10
                             Volts,    240
                             Phase,   1
                             HZ,        50
                             P,F.       1.0
                             RPM,      1500

Plant No,                36876LB
                             KVA/KW  10

Control box 240v;   BKB Electric Motors Ltd.
                             Regulator No,    V259/47
                             KVA   10
                             Volts  240
                             HZ     50
                             Year, 1/63
                             Type,  3C/230
                             Chassis, R42
                             Amps,    6.5
                             OHMS,    20.6
                             S/No.     27028/47 

This control box internal panel  has plugged into it an additional regulator named, "REGOHM" u/s patt. no.2550779. Norwalk. Conn. S/N, 17384.

At 8kva the rpm is 1510 with no sign of strain or black smoke from the engine and it does not bog down with further loading. The 8kva load is just convenient for my trials.

The power factor at this load is unkown to me because I don't know how to measure it.
 
I would be pleased to learn of repairers and testers for the electrical bits and pieces like these if you know of any still about. Also for any literature on the alternator etc. There was a repairer on ebay for the startomatic controls for a long time, but not at the moment. Me should have kept the detail when I could.
My preference would get it to produce the Nat. Grid minimum volts at full load or certainly 216volts as against the 200v at 8kva. It is a transformer controlled alternator with rectifiers [x2]. However there is no air gap facility [that I can see] to adjust volts.
I also don't understand why the voltage trimmer has no effect on the volts either no load or full load. May be if it could be determined that it is or not working and move towards its repair/ replacement , then may be dial in the volts nearer to the 216v under load???
Many thanks again.         
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ronsine
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« Reply #8 on: November 25, 2015, 11:52:24 AM »

Hi
As others have said the residual magnetism is ok as if not it would not excite at all!
I have considerable experience of generators and you may have a problem with the power factor being low or a faulty avr depending on the excitation system fitted.
If non avr system the voltage is usually very dependant on speed.From the info you have supplied and the lack of voltage trim it sounds like it has an avr.If that is faulty a suitable aftermarket unit can be bought but some testing would be advisable with seperate excitation before going down that route.
Do you have an alternator circuit diagram available?
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ronsine
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« Reply #9 on: November 25, 2015, 12:17:30 PM »

As a general rule most simple excitation systems ie capacitor excitation with an auxiliary winding don't like non unity power factors and the rating plate will often just give a unity power factor rating.
avr and compound excitation systems are normally ok and I would always run domestic loads which could include low energy lightingetc of an avr controlled machine as the best practice.
No alternator will like a capacitive load and large voltage excursions and equipment damage often result from doing so!
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oliver90owner
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« Reply #10 on: November 25, 2015, 05:20:32 PM »

Hi Deryk,

Steady on!  I am no expert.  I regard myself as a 'Jack of all trades'.  I have a few gennies knocking around, but nothing as big as 10kVA, currently.

The air gap will actually be a pack of shims between the base and frame of the transformer.  Increase or decrease thickness of shims to alter the air gap and thus the voltage.  This needs to be checked, after running at full load, after changing.

Your voltage control trimmer seems to be defunct.

This generator appears to be a genuine 10kW machine as the power factor quoted is 1.00.  They used to be honest back then; nowadays, a 10kVA machine is usually/often denoted as 0.8PF, so only a true 8kW on a resistive load.  So it may well manage 12.kVA at 0.8 power factor.  That would be driving mostly wound components - transformers, motors,  electrc welders, etc.

On a similar scale, your 8kVA load could be as little as 6.4kW, so you really need to load her up with 10kW of resistive load and see what you get after that.

Possibly the voltage is low simply beause the voltage trimmer is not working.  I would be checking that, initially.  But it may have been replaced by the bolt-on AVR, which may need adjustment/repair/replacement.

RAB
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ronsine
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« Reply #11 on: November 25, 2015, 07:05:58 PM »

Sorry to contradict but an alternator is an amps producing device so is sized in kva, the engine is the kw producing part.This means that kva is limited by the alternator and the kw by the power output of the engine. So you can have a 20 kva alternator on a 10 kw power output engine.This was sometimes done for motor starting loads where the current was high but the power was lower...
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oliver90owner
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« Reply #12 on: November 25, 2015, 08:35:45 PM »

Simple basic physics.

Watts =  Volts Amps

Holds for all resistive circuits where Ohm's Law holds true.

Wherever alternating current is concerned, the assumed voltage is that of the equivalent DC voltage.  A factor of root two (1.414) is used for single phase sinusoidal waveform, per eg.  However, whenever resistance, reactance and capacitance get involved, there ard further factors to take into account.  This is reported as the Power Factor.  Purely resistive circuits have a PF of 1.00, unity, one.  That means the Wattage is the same as the VoltAmps.  When the PF is 0.8, the true power drawn is only 4/5 of the indicated VA.

Hence, there is a difference of indicated versus true power used.  Abit like in the c days of competing amplifier/hi-fi systems.  Some would calculate the power output in 'root mean suare' and some would quote the same value as 'music power'.  The 'music power' system simply gave the impression, to the unwitting, that the output was higher than it really was, if they compared the two systems without understanding the differences.  Same with air compressors - some are honest and quote 'free air' volumes while others quotethe volume compressed per unit time, while ignoring the fact that not all that air actually progresses to the tank.

Not all generators perform at all power factors equally.  Not all generators will produce 20% more at unity PF, so not all generators perform equally efficiently at any particular PF.  This one may not produce 12.5 kVA @ 0.8PF, even though the engine power required is exactly the same as for 10kW @ 1.0PF.

Let's be clear here.  One Watt is one Joule per second.  One Volt Amp is only one Joule per second while Ohm's Law appies.

Joules is a measure of energy, VA is not necessarilly the same; it can be or can be less, but never more.  Engines are measured only in kW because they never have any 'lead' or 'lag' to take account of.

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ronsine
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« Reply #13 on: November 25, 2015, 09:03:19 PM »

Yes...But if the alternator plate says 10kva at unity power factor then the current available from that alternator is limited to that value..
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listernut
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« Reply #14 on: December 11, 2015, 05:08:57 PM »

Hello and thanks to all who have offered help on the problem of the under volting HA 2 Lister Generator.

The problem is now rectified with absolutely positive results. Many thanks to     " ronsine"    who journeyed to work on the unit with diligence, perseverance and professionalism throughout the day and to a very positive and welcome result.  User error on earlier wiring tidying was the prob. However, without wiring diagrams,
Ron worked through knowledge, experience and determination to  save the day. Thanks Ron.
It is now producing 240v at 10.4kw load together with a P.F of 1.0 and 1510 rpm.  Great!

 Thanks again Ron.

Thanks also to this forum, without which Ron's help would not have materialised.

My recommendations to all in need of these skills is..... ronambac@hotmail.co.uk

Regards to all

deryk
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