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Question about genset on 1950 CAT diesel D315

oldsdroptop

Registered
I have just purchased a D315 CAT genset. After spending hours figuring. Out the fuel was about the color of raw sewage from a septc tank. I ended taking a temporary gas tank from a 5 gallon gas can. Now I have the motor going I need to figure out this genset. It has a belt driven exciter on top of the generator. Will I read 110 volts on the leads coming out from the gen? I am using a Fluke 87 multi-meter to check it for power. I am. Reading 3.5 volts at 1200 RPM and 5.5 volts AC at 1800. My question is on a gen of this vintage will I need to have a good load on the gen to get. an accurate reading from this vintage unit? I am pretty new to this. Generator hobby, so I plead ignorance here. I know this is a really old unit and may work differently than what I am used to working with. Thanx for thhelp guys. David.
 

armandh

Sponsor
Last Subscription Date
09/02/2010
I ended taking a temporary gas tank from a 5 gallon gas can. Now I have the motor going I need to figure out this genset. It has a belt driven exciter on top of the generator. Will I read 110 volts on the leads coming out from the gen? David.
probably not

there should be a name plate on the generator and the belt driven exciter

first the exciter has to put out DC and needs some residual magnetism to get going. may not be any after a long time unused

that then feeds the field of the main AC generator

the name plate may help to determine the output

pictures help
 

oldsdroptop

Registered
ok...here are the pics of the unit in question...I'm just trying to establish if I'm doing everything right as far as testing it properly for voltage....the wires inside the exciter are a bit rusty on the screws...(the bottom 2 plates are MIA) so the wires are exposed on the bottom of the exciter. I cannot find any plate on this thing anywhere on the generator or exciter.....I guess 60 years will take it's toll on a unit...it's in really nice shape as you can see...thanx for the help guys I really appreciate it. I love kitty CATS.....:)David
 

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Wayne 440

Registered
Nice set. :D Lots of those were made to run at 1200. Be careful about spinning it up to 1800 unless you are sure that is the designed speed.
 

oldsdroptop

Registered
Wayne it has a position where a pin drops into that runs it up to 1800....when it's left in low speed its 1200RPM....and when you pull the lever up completely the engine shuts down. The only markings on the gen are the numbers 240 480 (voltage I'm guessing) below that is 2L328 and the third row is 40 RH 20 which if I had to guess deals with Right Hand rotation. These numbers are stamped into the case on the gen on the right hand side of the gen. There are 6 wires that are twisted together with large twistlocks. I was told these are the high power hook ups. I was told the 3 single wires are for the 220 2 hot with 1 nuetral wire.....but again I'm only seeing fractional amounts of power from this gen. I have a feelin its in the exciter assembly. thanx for the help guys. David
 

BTPost

Moderator
Staff member
Age
70
Last Subscription Date
12/29/2008
Take those numbers, and call your local CAT Distributer, talk to the Parts Guy, and he should be able to look them up in the CAT Build List, and give you all the Genend Info, about that specific Unit.
 

Jim Rankin

Registered
Age
58
I never had any luck with CAT unless you can give them a serial number off the machine. I have a slightly newer one than that with what looks like a CAT part number just like your 2L328 stamped into it, but no help from CAT without an arrangement number or serial number.

Sounds like you have 9 leads out of the generator housing. Pretty typical for an old CAT set. Most of them had 3 phase Y connected generator ends like yours. You mentioned there were 6 leads with twistlocks on them? If they are in pairs, (connecting 2 leads each time), then your generator is likely connected in series Y for the 460 volts 3 phase, not single phase. The only thing you don't mention that should be there is a neutral (sometimes marked L0 or T10).

DO NOT DISCONNECT ANY LEADS unless you see that they are numbered with ledgible numbers! The way they are connected is good information to have if you don't have any numbers on them. You will likely be able to use 2 lines and the neutral to get 120/208 single phase out of the generator for 2/3 of the full 3phase rating (which you don't have I guess). I would guess about 40 kW or so on a D315 at 1800 rpm.

You need to ensure that the brushes of both the exciter and the main generator rotor are free to move up and down in the guides and that the commutator surface of the exciter and the sliprings of the main rotor are clean. Do not have to be shiny, black discoloration is normal, but cannot be corroded, rough etc. If needed, fine grade sandpaper can be held against those surfaces to dress them while the generator is spinning over. Special stones are made for that purpose and are a lot easier to use than the sandpaper.

If it still won't build up after cleaning and checking the brushes, the most likely problem is that it has lost too much of the magnetic field that stays in the iron between runs. This residual field creates enough "residual" voltage to allow the generator to build up to full regulated voltage. To restore the residual, apply DC voltage from a small battery like a lantern battery or very carefully from a 6 or 12 volt starting battery to the brush leads of the exciter or the main generator. You need to determine the correct polarity (matching + and -) and just touch the wires from the battery to the leads for a second and see if voltage builds up. Best to have a volt meter connected and measureing voltage while you're flashing the field so you can see what it does.

BE CAREFUL! It is supposed to make voltage and may unexpectedly do so at any time. Somehow a generator doesn't seem as dangerous as utility power, especially a "dead" generator, but still be very cautious. Even the DC power from the exciter running down to the brushes on the main rotor is dangerous.
 

Jim Rankin

Registered
Age
58
I forgot to say that there is supposed to be a serial number plate riveted onto the engine block above the starter on the governor side of the engine. Look just below the head gasket line for a small tag about 2" x 1" held on by two drive rivets. If it's not there any longer, the number was normally stamped into the block before the tag is put on, so clean carefully between the two rivet holes.

When you call CAT for parts, you want the oldest guy there! Lots of the younger ones "don't know how" to go into the microfiche system that most dealerships use for the old equipment parts books. If it ain't in the computer, they aren't interested. CAT has a website where they have reprint manuals etc for their old equipment. I would look through the "engines/power units" section.
http://www.cat.com/cda/layout?m=90800&x=7

If flashing it doesn't get it going, a lot of the old ones have build-up relays on them and there are various other components in the regulator cabinet that could be defective, maybe some fuses in there that could be blown etc. The bolt-on cover on the side of the box on top of the generator should get you into it. The same advice as the output leads applies here........don't disconnect anything without first marking it so you can put it back.

One thing you can do to check the basic health of the generator is to read the voltage on all combinations of the 3 leads and perhaps each lead to the frame of the generator or more appropriately the neutral lead. Even the residual voltage should be equal between each pair of lines A-B, B-C, A-C and A-N, B-N, C-N. The Line-N voltages should be about 57% of the L-L voltages if everything is alright inside.

You do not have a single phase generator with that many leads and stamped 230/460.
 

Nick cox

Registered
Hello i have one of these sets before you do any testing read the plates on the side of the gen set for volts and amps also the phase this set may be 3phase at 230 v a phase 80amps a phase too also read the engine plate on the inlet side under the manifold this will tell you engine hi idle speed that will possable be 1200rpm that will give you the max speed to drive the unit if thats the correct rpm it was made for some sets are higher this is inportant to find out before you do any setting and testing from the past sets i have worked on U S navy is 230v at 60 herts at 1200 rpm these sets are very good at the day built was top spec very reliable
 
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