Old Lister Diesel Generator

I've been using an old lister diesel generator to run a TV, lights, pone chargers etc, but am a bit of a simpleton when it comes to electrics and have been having a few issues, so was hoping I might be able to find some answers here.

I'm running appliances directly from the outlet, but something doesn't seem quite right- the TV occasionally turns off and back on, phone/tablet chargers are getting very hot, and when I use a mains 4 amp car battery charger, it is hardly charging the batteries at all (tested the charger by running it off an inverter and the needle indicates it is charging normally, hovering around 4amps, but switching to power from generator it drops to near 0).

Any ideas what might be going on? It makes no sense to me that some equipment seems to work normally while other things don't, but obviously that's just down to my ignorance! Would really appreciate any thoughts on this.

Is the generator producing 230 volts or 110 volts ?

The symptoms you give suggest it is 110 volts ( or slightly less ).

The TV may be 110 - 230 volts so will work.

The phone chargers will taking the same power but at half voltage they will be taking twice as much current and thus likely to get hot.

The battery charger if supplied with 110 volts will not produce more than about 9 volts and thus not charge a 12 volt battery.

Thanks for your reply, it's connected to the 220v outlet. It has both 110 and 220 and a switch between the two, I wonder if it's possible that it could be generating 110 through the 220 outlet?

Old diesel generators can do anything

The engine speed, revs per minute, is often critical to get the voltage correct and stable and hence the diesel's speed governor needs to be in good order.

If you have a multi-meter you could check the voltage.

Adding electrical load ( within the generator's rating ) should not slow the engine's speed for more than a second or two. If it remains noticeably slower until the load is removed then the speed governor needs attention.

Excellent, thank you- measured the voltage which was at 140. Fiddled around a bit, increased the engine speed and voltage increased to 220. Might even be able to get it to run the washing machine now!

The Lister engine was used to drive many generators with many methods used to control them.

There was one used a lot on the Falklands where the generator was also a started motor and switching on the lights auto started the generator. Often disabled by farm managers as there was a tendency not to check oil before starting.

Some used a large capacitor but I never worked out exactly how. My method of repair back in 1980 was to swap parts good one to one which was not running until fault swapped then order up that part.

Seem to remember out lighting towers used a Conveyors generator which had two sets of field windings. One set in series the other in parallel the series set had a huge rectifier and parallel a small one and both also had resistors to set the output. The generator was first set to 1500 RPM I used a frequency meter and set to 50 Hz but rev counter would do the same. If anything set slightly high. Then the parallel winding resistor was set to give 240 volt then we put on a load quite high often full load and the series resistor was set to 240 volt.

As load increased the voltage would vary but would be some where between the 220 and 240 range it was a little hit and miss. The output coils rotated with static field and four slip rings.

However the larger sets used a completely different method. These used an AVR to supply current to a static field. This caused an AC voltage in one half of the rotor which was rectified by rotating diodes and fed to other half of rotor which in turn caused an output from the output stator. These needed the 12 volt battery to get everything started. The output was in the form of 12 windings which could be configured for 55-0-55, 63-63-63, 240 single phase and 415 three phase and the output was very steady.

With the larger generators we would synchronize with other generators and so the droop was very important. Normal generators had a 10% droop but the specials could be as low as 2% droop with electronic governors.

Sizes varied 1.5kVA to around the 50kVA after that tended to use RR engines 250kVA and 500kVA the permanent generators were Ruston at 1.5MW each.

I returned to UK where we used far bigger just two generators at 600MW each but also 12 x 1.5MW Ruston engined generators as stand-by.

Next was 4 x 400MW units in local power station. Oddly they still used rotating diodes exactly same idea as with the little 12.5kVA unit on the Falklands.

Today small generators have moved on. The output is converted to DC and then back to AC at 50 Hz what ever the engine speed. The new inverter generators are another world.

But before anyone can help we really do need to know more. So what can you see? Is there an electronic unit, are there resistors, or a capacitor? Does it seem long with two completely separate field coils or compact. Does it have slip rings if so how many. Does the generator start the engine.

Direct drive 750 (8 pole) 1000 (6 pole) 1500 (4 pole) are the set speeds. With belt driven depends on pulley size.

A note of caution here.....

The engine speed sets the frequency of the AC power produced.

The AVR (automatic voltage regulator) sets the output voltage.

If the AVR is faulty, the machine will give a zero or reduced output. Increasing the engine revs may appear to increase the output voltage but will also change the output frequency.

The OP needs to be sure that, by increasing the engine revs in an attempt to correct low voltage, he hasn't also increased the output frequency way beyond 50Hz!

AdrianUK said:

A note of caution here.....

The engine speed

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Normally

AdrianUK said:

sets the frequency of the AC power produced.

The AVR (automatic voltage regulator) sets the output voltage.

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If fitted with one

AdrianUK said:

If the AVR is faulty, the machine will give a zero or reduced output.

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Only if it has an AVR

AdrianUK said:

Increasing the engine revs may appear to increase the output voltage but will also change the output frequency.

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In the main but not with inverter models

AdrianUK said:

The OP needs to be sure that, by increasing the engine revs in an attempt to correct low voltage, he hasn't also increased the output frequency way beyond 50Hz!

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I would agree one sets speed with a rev counter or frequency meter before looking at other settings. You do not set speed to give correct voltage.

However many of the old generators had diodes and resistors to set the on and off load voltage. The on load voltage used a selenium rectifier unlike the silicon type these can start to fail but not completely so it not a case of work or not work and the resistor has to be adjusted to match the rectifier.

Even the open circuit diode pack has 4 diodes and if just one or two fail this can cause a voltage drop.

Also common to be designed to run either 110 or 240 just using wrong tapping can cause low voltage.

With an AVR then likely it would auto compensate but with the old pre-AVR system you can easy get reduced voltage. The problem is on load and off load voltage are separate so one has to test both on load and off load as off load it could be 230 volt but on load 330 volt if for example a diode blows in the small silicon rectifier.

Some old ( very old ) Lister Diesel generator were devoid of any electronics and were just engine and a basic generator set up to power a specific load.

The engine speed was manually adjusted to get the required voltage into the load and the frequency was what ever happened to be generated at the speed that provided the required voltage into the load.

Thanks for the info everyone. I think the engine was probably just running too slowly, is there a way to measure the frequency, and what is the danger of it being too high? (Like I said before- I'm a bit undereducated in these things!).

The generator is an old ~1970s 5kva one on wheels (the type the highways used to use to power temporary lights at roadworks apparently), don't know much more than that but am trying to identify it at the moment, as when i went to start it last night and the starting mechanism fell apart, so I haven't even had chance to heed the words of caution on here yet!

Multimeters like this one can measure frequency. Likely the easy way is an energy meter mine from Lidi I think has frequency This one on Ebay says it does volts amps watts and frequency (hertz) and is likely the easiest way to set things up.

You could use a mechanical device like this but they tend to be expensive so likely plug in energy meter is the cheapest option.

sherburn said:

The generator is an old ~1970s 5kva one on wheels (the type the highways used to use to power temporary lights at roadworks apparently),!

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In which case the frequency would not need to be regulated to 50 Hz. The only requirement would be that the voltage was correct for the lamps.

The on site instructions probably had little more than "start slow and increase speed until lights are bright enough "

sherburn said:

The generator is an old ~1970s 5kva one on wheels (the type the highways used to use to power temporary lights at roadworks apparently), don't know much more than that but am trying to identify it at the moment, as when i went to start it last night and the starting mechanism fell apart, so I haven't even had chance to heed the words of caution on here yet!

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Keep the engine, which will probably last for ever and run on anything vaguely oily which burns, replace the generator and voltage/frequency control?

A switched mode power supply turns AC to DC as first stage and often has a very wide voltage range.

So much depends on what is being used. A simple LED bulb can have a voltage range 150 ~ 250 volt a lap top 100 ~ 250 volt but an old fluorescent lamp (Not HF) could be limited 220 ~ 230 volt under it will not strike and over it over heats so much depends on what is being used.