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Messages - Ian

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1
Thanks for all the replies guys.

My take, then, is that my setup is not perfect but as long as things stay within the expected behaviour patterns and the kit stays reasonably cool, there is little to worry about.  Similarly, whilst something could be done to improve the setup, knowing exactly what to do is not simple so it is best left alone.

Regards and once again thanks for the help,
Ian

2
jzeeff  - I assume the meter analyses the phase angle between the voltage and current and integrates the results (but I do not KNOW this for sure). The meter is non-moving-parts digital.

I agree that the load will not be such that the generator produces a perfect sine wave but I do not know about harmonics. As my goal is essentially to produce DC, the generator AC output is almost of superficial interest as long as the generator is happy to handle the load it sees.
 Having said that, I sure wish I understood more about what the generator really sees. I am so in the dark, I do not know if the load is essentially resistive, leading, or lagging!

Is a non-linear harmonic load anything I should seriously worry about ? (Your post would lead me think that I SHOULD be worried...)

mobile_bob - Yes, agreed. The bridge rectifiers I am using are rated at 1000 volts reverse voltage and 16 amps continuous. they are bolted to a 0.3 degree C/W heatsink.

I think most rectifiers fail open circuit but in the event of a closed circuit failure, AC will pass through and then a reverse polarity diode will allow this current to effectively short circuit - which should trip the 16 amp three phase breaker (hopefully before any catastrophic damge is done to the capacitors of the inlet stages of the inverter due to reverse polarity).

I ran this setup for the whole of the last heating season and added around 1000 hours without any obvious issues that I can see. The previous heating season, I was operating on single phase 240 volts without any obvious issues either. But, of course,  it does not mean that there ARE NO issues just because I am ignorant and cannot see them....

Regards,
Ian

3
Hopefully, this is on topic, and if any of you guys can offer a reply - may help me and others too....

My ST 7.5 kW 3 phase generator feeds to a full wave rectifier and the resulting DC is fed to a grid tie inverter. Just to give the full picture, the ST rotates at about 1500 RPM and outputs around 380 volts RMS phase to phase and is held purposely this low by an AVR. The DC measured under load at the inverter is about 450 - 480 volts DC when the inverter is outputting around 3.5 kW single phase into the grid.

I was wondering if the generator was seeing a resistive load (from the full wave rectification to DC) or a capacitive load (capicitors in the inverter), or an inductive load (inverter transformer) but could not find anyone who could give a definitive answer. So I installed a 3 phase kW hour meter between the generator and the full wave rectifier which has pulse indication of "real" power and pulse indication of "reactive" power. The meter shows one thousand pulses per kW hour on each of the "real" and "reactive" LEDs.

In operation, the "real" power LED pulses at about one pulse per second (as you would expect for a grid output of about 3.5 kW) and the "reactive" LED pulses about once per 6 seconds. In other words, the "real" LED pulses six times for each of the "reactive" LED pulses.

I have assumed this means I have a power factor of about 0.8 (5/6ths of the power is "real" and 1/6th or the power is "reactive". Is this a correct assumption ?

Can I tell from this information if the load seen by the generator is capacitive or inductive ?

Many thanks for any help in shedding some light !

Regards,
Ian

4
Waste Vegetable Oil / Re: Injector Pressure
« on: April 24, 2009, 09:09:30 PM »
Are there any significant downsides to increasing injection pop pressure ?

Regards,
Ian

5
Waste Vegetable Oil / Re: WVO processor update
« on: July 13, 2008, 07:57:07 AM »
I am absolutely dumbfounded how much water can be retained in the oil .... I would like to keep the mist wash step but this might turn out to be too expensive an option in either time or energy.

Jens - Could you please expand a little on this ?

How much water would you estimate was still in the oil ?
Is the oil still crystal clear whilst still containing this water ?
How do you know that you have removed all of the water at the end of your processing ?

Regards,
Ian

6
Listeroid Engines / Re: Mixed fuel. Would it work?
« on: July 11, 2008, 08:09:41 AM »
Dino and veggie mix just fine. Animal fats or the higher melting point veggies should not be used unless you can permanently heat them or keep them above their melting points.

Filter out water and any particulates and then you have good fuel. Starting from cold is OK with a glow plug or start up and shutdown only on volatile dino fuels. Once up to temperature, and assuming you heat the fuel in the high pressure line, you can run just about any fuel.

With the high melting point fuels, you may have to be prepared to clean the injector tip a little more frequently than you would with dino fuels alone.

I hope this helps.

Regards,
Ian


7
Generators / Re: ST Slip Ring Flat Spot
« on: July 10, 2008, 10:06:18 AM »
It is not as easy as I would have like it to be....

Once you have got the rear bearing off (this is the easier one to remove but you will either have to strike it off or use a hydraulic puller), unsolder the slipring fly leads from the rotor copper. Cut and remove the lacquered fabric that holds the flyleads close to the rotor and then put a long reach puller on the slipring assembly. They are pressed on but I am convinced that some adhesive is also used.

Removing the slipring also destroyed it in my case - so maybe you could just hacksaw it off.

The splines on the rotor where the slipring assembly sit will need to be cleaned up before pressing a new one on.

Pressing a new on on is easy if you can line it up square to start with. Use an annular drift to push it all the way home before remaking the soldered connections and wire-ties to the rotor shaft.

The reason that I removed my slipring assembly was that it was not square and caused the brushes to oscillate and mis track the brass rings. After I replaced the assembly the new one was still not square but a little bit better than the original one. The brushes still oscillate and mis track but this does not appear to be a problem in use.

If I had your problem today, I would not, now, replace the slipring assembly unitil I had tried to repair the original.

So what is wrong with one slip ring being slightly smaller than the other ? If you were so worried about the rings being different diameters, you could also remove both brass rings (in situ) and turn up some new ones to slide onto the insulator whilst it is still on the shaft.

I hope this helps.

Regards,
Ian

8
Generators / Re: Alternative to those Chinese generators.
« on: July 07, 2008, 09:59:33 PM »
Rob - I am sure there are alternatives but you will have to look very hard to find a generator that is as low cost, simple, and robust as the Chinese STs.

Whilst it may appear that people here are not particularly complimentary towards the Chinese STs, they are by far the most popular generator to couple with a slow mover for the DIY types generally posting. They do not really go wrong. You may have to fix a few things on delivery (like bearings, brush alignment) but they are built like a tank and take a lot of abuse. Very few actually fail in service; some seem to fail whilst being tinkered with.....

For the money they are very hard to beat. if they go wrong you can fix most things (or buy a new one). Why would you want anything else ?

There are a number of vendors here in UK and they tend to keep reasonable stocks.

I hope this helps.

Regards,
Ian

9
Generators / Re: Knock in ST5
« on: July 07, 2008, 09:40:49 PM »
Doug - Yet even more good stuff. Many thanks.

Regards,
Ian

10
Generators / Re: Knock in ST5
« on: July 07, 2008, 08:44:32 PM »
There is some good stuff here. Useful and on topic (a pleasant change...). I have learned a few things too... Many thanks for the education.

RAB, I think in principle the bearings ARE pressed onto the rotor but I have never been able to get any of them on without GENTLY warming them through and then using a cylindrical drift on the inner race to set them on the shaft.

With regard to removing the bearings - the large fan end bearing is almost impossible to remove in such a way that I would want to re-use it. It is placed so close to the fan and the reach of the rotor requires that a very unusual puller will be required to operate on the inner race. Generally, the Chinese bearings are on VERY tight and I am convinced they shrunk them on at the factory. I have yet to remove one of these bearings without the aid of a hydraulic puller - and even then the hydraulic ram has been at its pressure limits before they give way with a "crack". As my pullers only allow operation on the outer race of the fan-end bearing (to reach the inner race, the fingers would have to be long and very thin) I would not want to re-use these bearings after the abuse I give them on removal.

lendusaquid, do you still believe that the knocking sound is the rotor moving axially ?

Regards,
Ian

11
Generators / Re: Knock in ST5
« on: July 07, 2008, 07:56:59 AM »
All 3 of the Chinese ST heads (from 3 different Chinese suppliers) in my possession have a (wavy) thrust washer ON THE FAN END and none on the slip ring end.

All the bearings as supplied were "standard" and NOT C3. I have replaced all the Chinese bearings with bona fide SKF standard bearings and they run just fine continuously without excessive noise or heat (at 1500 RPM or so).

The bearings are shrunk onto the rotor (front and rear) and the outer races are a good snug fit in the bearing housings. You should not be able to detect any end float by manually pushing and pulling. If you DO detect end float, then, as suggested earlier, you should apply some bearing "fit" as a minimum. If you can remove one of the bell ends without using a puller or a mallet, then the bearings are too lose in the housing.

Your knock under load could well be a cracked ball or race - probably on the fan end bearing. The only way to tell is to take the bearing out and inspect it. However, once you have the bearing out, in my opinion, you would be better to replace the stock Chinese bearings with a proper (standard) bearing.

I hope this helps.

Regards,
Ian

12
Listeroid Engines / Re: engine fell over during shipment
« on: June 25, 2008, 08:52:54 PM »
Probably 99% of all of these Listeroid engines are used in Asia and Africa. In most of these end user places there is no such thing as a fork lift truck or a delivery system - particularly at the end of the track where the farmer will be using the new engine. So, any kind of truck that is cheap and available will be used to deliver the new engine to its destination. Forget any kind of fancy systems of levers and pulleys and cushions to get the engine off the wagon. The driver and his mate will manhandle the crate to the side / end of the truck and then push it off. They will not look for a soft patch of earth for it to land on. Once it is off the truck their responsibility is complete and they will drive away - leaving the farmer to "somehow" get the engine to where he wants it.

If 99% of all these engine survive this treatment and keep going without any air filters or oil changes - for years, then there is a very good chance that yours, which has been positively cosseted in its delivery to you, will be just fine.

Not sure what a dial gauge will tell you. the chances are that ALL these engines have a high degree of run out. If you DO check with a dial gauge - please set your action standards BEFORE you measure. What are you trying to achieve ? What level of run out is acceptable (and how will you know). If you find run out greater than your action standard, what will you do about it ? Sometimes, it is better to just run the thing and not give yourself sleepless nights worrying about things that are of little consequence.

Regards,
Ian

13
Generators / Re: Power Factor
« on: June 23, 2008, 10:58:43 PM »
jzeeff, I have two single phase ST alternators and I have used both at some time. The first one I tried ran very cool (only a few degrees above ambient) and was only taken out of service due to bearing failure and a "clunking" sound when turned over slowly. The second alternator ran much hotter. I do not recall the actual numbers now but it was noticeably hotter - maybe 20 - 30 degrees C hotter than ambient.

jens, now I have gone to 3 phase, I assume the ripple in the full wave bridge rectified DC output to be within the stated <10% specification of the SMA inverter, so I simply take this DC and plug it straight into the inverter (no filter caps, no batteries, etc). I run the Listeroid at 540 RPM and the STC at around 1500 RPM (50 Hz here in UK) with the field rheostat turned right down so I see about 530 volts DC cold, unloaded (about 520 volts DC warm, unloaded) and around 495 - 505 volts DC, loaded.

I hope this helps.

Regards,
Ian

14
Generators / Re: Power Factor
« on: June 23, 2008, 09:39:22 AM »
Again, many thanks for the replies.

I have now installed a 3 phase STC 7.5 kW alternator (from Listerclones.co.uk). Again, before putting this generator into use, I stripped it down and replaced the bearings with SKF sealed units and epoxied anything that might move about on the rotor, plus replaced all fixings with stainless steel versions. This unit was not "balanced" with any weights or drillings and is branded "Kapur". The rotor is a skewed type and all the stator slots are filled. It is wired at the stator as 3 phases and common neutral. All the crimps in the doghouse were good and the cable interconnects are very substatntial but flexible tinned multistrand type which must be good for 30 amps or so.

Using rectified power from the 3 phase generator, the SMA Sunny Mini Central will not connect to the grid under the standard "PV" MPP setting that it was very happy to do when operated from rectified single phase (it shows "offset" on the display panel which the manual indicates is a failure to synchroinise internal diagnostic settings) - but it works very well in "(Wind) Turbine" mode.

In use, the generator makes a pleasant (normal) humming sound and exhibiting no obvious vibration or imbalance; when outputting the full 6 kW, it hardly gets warm with the case surface temperature only getting about 10 degrees C (18 F)over anbient tempertaure.

Regards,
Ian

15
Listeroid Engines / Re: An Affordable Electric Genset Governor?
« on: March 22, 2008, 08:31:14 AM »
Hey listeroidsusa1, how is the governor setup and testing going ?

Seems to have gone quiet again. Any news ?

Regards,
Ian

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