Author Topic: Lister HA and Brush RS1B generator  (Read 1344 times)

mobile_bob

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Re: Lister HA and Brush RS1B generator
« Reply #30 on: August 24, 2021, 12:06:06 AM »
ok

this is what i am thinking now that we have some data to work with

one or the other of the following needs to be checked, as either might be the cause

a. you might have a defective diode or more in the rectifier bridge, or

b. the brushes are dirty, and i am suspicious of them being so.


the slip rings look bright and shiny, did you clean them? or did it come that way?
have you cleaned the brushes?

reading your results, it appears that you have virtually no voltage with the field connected to the rectifier bridge,  while the voltage jumps up to 177vdc on the rectifier with the field disconnected.

what i am thinking is this,

if the brushes are not making good contact, there will not be enough power transmitted across the brush to sliprings or rather visa versa, when the field load is applied. it wouldn't be the first time that i have seen full voltage on an open circuit but have it fall away when the load is applied.  and it appears from your report that is what is happening.

when you apply 24volts to the field the voltage climbs up to something like we would want to see, or close to it.

so the field has two possible sources of power,

1. when you provide 24vdc direct to the field, then you get output

2. when you leave it to the original source to the field you have no output.

so we need to start at one end or the other in the current supply to the fields, and i am thinking maybe start with the brushes first, as they are pretty easy to eliminate.  are they connected to the brush holders with bonded copper cables? i assume so,

as stated earlier, put a piece of 200-400grit paper with the back side on the slip ring and the abrasive side facing the brush, and work the paper back and forth with the brush spring providing the contact force, a few stroke and you will see some powdered carbon, that should be good enough, do them all.

if you didn't clean the slip rings, give them a bit of scrubbing just for kicks.

let us know how you come out

i am still thinking about this machine! and i think we are getting closer to the root cause.

bob g

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Re: Lister HA and Brush RS1B generator
« Reply #31 on: August 24, 2021, 12:47:26 PM »
Hi Bob
I had previously cleaned the  brushes but have done the brushes again this morning with 400 grit paper. It has not made any difference.

The rings I have rubbed with some 3m scotch brite.

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Re: Lister HA and Brush RS1B generator
« Reply #32 on: August 24, 2021, 12:51:19 PM »
To recap slightly. I have zero dc voltage coming from the stator.
What are the likely causes for this?

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Re: Lister HA and Brush RS1B generator
« Reply #33 on: August 24, 2021, 12:56:47 PM »
I have continuity between all of the slip rings and brushes. So metering between ring 1 and 2 gives continuity, 1 and 3 and 1 and 4. Is this right?

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Re: Lister HA and Brush RS1B generator
« Reply #34 on: August 24, 2021, 01:02:23 PM »
Another question.
When flashing the stator windings do you do it either engine running?

mobile_bob

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Re: Lister HA and Brush RS1B generator
« Reply #35 on: August 24, 2021, 02:43:35 PM »
ok silly me, i never thought to actually read the complete manual, but it has a diagnostic flowchart near the end of the manual.

page 11 i think with the info you have provided tells me what i was thinking we were closing in on, but didn't want to say.

from your information

you stated you ran the engine, connected 24volts to the field and got 170volts between each phase coming off the machine?  iirc that is what you found.

if you go to page 11 and follow down the middle of that page, you will find a section wherein

"start the engine, and if the voltage output is still low, apply 24volts to the field... and if the output is approx 220 for a 420 volt machine or ... 170 for a 220 volt machine..."

then to the left of the flowchart,

if the voltages are equal between phases... (and i believe you report that)

then below that on the left column

"fault is in the OREX unit"

"inspect transformer and replace if necessary"

*** insert here:  in the flowchart it tells us to disconnect the capacitors from the output and recheck, so follow the chart and do that next and see if it is "possible" that shorted capacitors could be the fault. it doesn't seem likely to me, but check none the less as the following is much more involved.

back to follow "inspect and replace the transformer if necessary"

so, i think if the aforementioned is correct, that is if you have ran the engine/generator and if you have applied 24 volts to the field connections and if you had equal voltage reading off the output of either 170 or 220, then the only thing left is the transformer unit.

we will then have to pay special attention to that unit
and check all connection carefully, clean and inspect and tighten everything
check for continuity through the windings, check for shorts to the steel laminate cores,
and check for signs of overheated windings, flaky insulation, etc.

i have no idea if a replacement is available for the unit, or if so it is affordable.

so if we find that there is shorts or some other fault in the windings, and no other transformer is available, you have a choice to make...

1. scrap the project, (certainly not something i would do)
2. find a rewind shop and have them rewind the transformers, or
3. take on the rewind project yourself.

the transformer should be fairly straightforward to rewind, as the core lamination's are similar to an audio output transformer wherein the E and I lamination's are not interleaved. the E lam's are all together and the I lams are riveted together. so you can remove the I lamination stack (be careful to note the packing shim stacks, measure them carefully and put them away somewhere safe)  then the coils can be removed from each leg of the E lamination's.

i don't know if the individual coils are wound on bobbins or not, if they are that makes life a bit easier, simply unwind the coil noting the number of turns, number of turns to each tap, and wire size, it appears that there will be two sets of windings, one over the other, one set of smaller gauge wire, one set of heavy gauge wire.  keep careful notes of how each is wound, and if there is a separator paper between the two sets of windings and all taps.

then find a supplier for the magnet wire, get more than you need, it can be found at a motor rewind shop, explain to them what it is you are doing, and they will generally sell you the wire, and in some cases they will give you enough wire for the job.

if you don't have a bobbin, you will have to make a wood form that has the same dimensions as each leg of the E lamination stack.  be extra careful to provide stops to keep the coils the same length as the originals, because they have to not only go back on the leg of the E stack, but allow the riveted I stack to be able to fit back and contact the E stack (the shims will hold them apart, but we want the winding coils to allow for contact between the E and I stacks)

then it is a matter of setting up to rewind each coil, with the taps, and insulation as the original.

trial fit the coils, assemble the transformer, make the connections and test the output.
if all is good, as it should then be, take it all back apart again, and take the transformer to the motor shop and have it vacuum dipped and baked. that will set the windings, and provide for better insulation that will last as long as the originals.

of the three rewind area's of your generator, that being the field, armature, transformer
the transformer is in my opinion far and away the easiest one to rewind successfully.

i had hoped that we wouldn't have got to this point, but if as you reported earlier with 24volts to a running generators fields you got an even 170 or 220 out of the machine on each phase, there really isn't much else to be looking at.

at this point i would be taking a very critical look at all the transformer connections, the condition of each of the coils, continuity, grounds/shorts and if possible take it to a motor shop to see if they can do some meggar test, growler test or whatever to determine the health of the transformer. then depending on the test outcome, the direction will be apparent, and possible decision made.

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Re: Lister HA and Brush RS1B generator
« Reply #36 on: August 24, 2021, 03:28:32 PM »
Ok Bob Iíll work through that, Iíll keep you posted.
Thanks.

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Re: Lister HA and Brush RS1B generator
« Reply #37 on: August 24, 2021, 06:18:24 PM »
I have disconnected all transformer connections and done some tests as below.
There are no shorts to ground.
Continuity between in put and out put is good.
Not sure how to test tappings, but again no shorts here or indeed any continuity with anything on the tappings.
I have a megger and all cables have very good insulation.
All three transformers behave the same.
Is there anything else I can do?

mobile_bob

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Re: Lister HA and Brush RS1B generator
« Reply #38 on: August 24, 2021, 08:56:32 PM »
man,, there is something we are missing here!

now that you have the transformer out, and i assume all the leads can be taped off
so we can do some more testing?

if so, lets power up the field (blue wires) removed from the rectifier x and xx

put 24vdc to the two wires

start the engine and bring it up to speed,

check each phase on the output again, a-b, b-c and c-1 and note the output voltages
lets make sure we are getting relatively even voltage on each of the 3 phases

lets see what we get from that.

if you get somewhere around say 170 volts or more, can you apply a load to that? like a brush motor circular saw?  you guys use 220 single phase in england iirc?

the idea being i would expect the phase to hold a relatively steady output with somewhat of a load.

maybe an electric heater or something?

i have a load bank here that i can provide a load for about anything from 12 volts to 240volts, but you are there and i am here, so that doesn't help.

something else came to mind a bit earlier

you mentioned in the OP that the unit was recently acquired and had been sitting for 10 years?  and the selenium rectifiers released the magic smoke (toxic as it is).

there is a real possibility that someone was monkeying with the internal connections trying to make the thing work sometime back before it was put to rest (over 10 years ago).

it might be something a stupid as some wiring connections that have been moved around and not connected correctly.  this might explain why the selenium rectifier burnt up, when the problem originally was it probably just needed the slip rings cleaned up.

so, do the above test if you can

and if you are fairly confident the transformer is good, then i would suggest going to the schematic fig2 and go through every single connection to make sure everything is connected correctly.

i also read in the manual that a provision to shut down the field could be accomplished with the addition of a 15amp switch to short the field.  this i find quite strange, as a shorted field would through a lot of heat on the rectifier and transformer i would think.  however the manual states this as a possibility, so you need to check to see if there is a switch in the panel somewhere?  it is unlikely there is one, because how are you able to get 24 volts to the field if there is a blown switch?  but then again, maybe under load the 24volts isn't really 24 getting to the field coils?

can you take pictures and post of the transformer, from front and back, i would like to have a look at them.

i assume that the unit failed before it was put into storage, and left to sit for 10 years, what we don't know is who or what happened after it failed, and what was done to try to get it going again... that is always a big red flag in my book.

a lot of guys won't touch electronic equipment that has had other hands messing around in the insides,  not unless they specialize in that particular piece of equipment and have the exact schematics and other resources.

i recall a Zenith TV repairman years ago, he was about to retire and wanted me to take over the business... he told me "never ever, work on anything you don't have a schematic for, and never ever ever work on something someone has made a mess of"

now i don't know if that means it will be a real pain to fix, or something that in his experience can't be fixed?

a generator however is a rather simple piece of equipment and we have a schematic
so we are missing something,

so lets tape off all the loose wires, remove the field wires from the rectifier, power up the field, start the engine and see what voltage comes off each phase of the armature, note the readings, and then lets apply some load and see if the voltage drops like a rock or remains somewhere in the same area.

lets do that first

then lets take some pictures of the transformers and post them,

then lets reinstall the transformers and check each and every wire, to make sure it is connected according to the schematic.

and finally

are you absolutely certain the rectifier bridge is good?  i know you installed it to replace the selenium rectifier, but we sure don't want a bad replacement part to drive us crazy chasing other directions assuming it is good.  i don't trust any part these days!  and i don't much care who makes the part, it seems failure rates are much higher than they used to be.

this is turning out to be a fun project  :)

bob g
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Re: Lister HA and Brush RS1B generator
« Reply #39 on: August 24, 2021, 09:11:09 PM »
Ok Bob I will have ago at that tomorrow.

When I fired it up for the very first time I had 400 + volts show on the volt meter, after about 30 secs I thought I saw the volt meter increase considerably and by that time it had started to smoke so I shut it down.

I have tested the bridge rectifier and it is ok. All six readings are good.

Al

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Re: Lister HA and Brush RS1B generator
« Reply #40 on: August 25, 2021, 12:43:04 PM »
Hi Bob

I sprayed the coils and wire with a good anti tracking spray.
The thicker cables run right back to the brushes.
Not sure how I test the phases without these attached.

Al

mobile_bob

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Re: Lister HA and Brush RS1B generator
« Reply #41 on: August 25, 2021, 03:18:10 PM »
test leads right to brush holders
or if that is too hard connect some short wire leads

bob g
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Re: Lister HA and Brush RS1B generator
« Reply #42 on: August 25, 2021, 04:37:06 PM »
See pics of set up.
I,m getting 268 v across phases 1,2 and 3 and 169v across a phase and neutral.
I will try and find a kettle to put the single phase under load?

Al

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Re: Lister HA and Brush RS1B generator
« Reply #43 on: August 25, 2021, 04:58:24 PM »
Ok, with a 2500w kettle plugged in the single phase and neutral the voltage dropped from 169 to 159.

mobile_bob

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Re: Lister HA and Brush RS1B generator
« Reply #44 on: August 25, 2021, 05:50:38 PM »
ok, cool
that tells me that the field and armature along with the brushes and slip rings are good
so we have a basic machine that works

now we need to track down every friggin connection from the brushes to the transformer to the rectifier and then to the field

the problem is not in the basic generator itself,

with that big ass control box on top, i am wondering the wires coming off the brushes obviously go up there so that they can be applied to the output posts, so i am thinking that is where they also T off to come down to the transformer pack

do you have a picture of the innards of that control box?

i as well as you should be happy that the basic generator is doing what it should, it now comes down to finding the wiring fault

what i am saying, and forgive me if i am telling you something you already know, is...

with you supplying the field with 24vdc and getting an output voltage to an approx 2500 watt load, and noting the 169 vac dropping to 159volts tells us that the generator is doing what i would expect it to do... i would expect a few volts drop as there is no regulation that would normally be provided by the transformer action by design.

this outcome tells us that with excitation current (24volts in this case) the machine can make power.  so the problem is with the original excitation system, which is comprised of the transformer pack and the bridge rectifier.

you have tested the bridge rectifier and it tests good, so it leaves us with either the transformer pack, or something between the brushes and the transformer pack that might be located within that control box.

i don't see anything on the schematic, however it is not uncommon to have some other option either added by the OEM or by someone else after installation in the control box.
and that would not necessarily show up on the generic schematic.

what we have in the manual is a generic schematic, and from experience manufactures make changes over time and publish differing schematics to account for changes in design. 

so lets open up that panel and have a look? 

and if you can provide pictures (front and back) of the transformer pack, i really want a look at it too.

bob g
otherpower.com, microcogen.info, practicalmachinist.com
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