generator repair - Page 1
Forum section: electronics / repair

author: Boschi
author_rank: Regular Contributor
timestamp: April 11, 2024, 09:46:27 am
content: its a little out of topic for this forum, but since i cant find any datasheet and this thing works by various kinds of electromagnetical wizardry, here i am.this thing was gifted to my father, which now is asking me for help to make it running again. the guy who gifted him this thing received it as a gift too, in the same (non runnign) conditions that it is in now.initially i saw the brushes and i assumed it worked like a normal "modern" generator, ie i put a current on the stator and it changes the output voltage/current that it produces, but while spinning it put out like 35V with 5A, so i assumed the stator was shorted.after disassembly i saw that it works in 2 different ways, one is what i assume a asynchronous generator (in the rotor photo on the left), and the other an old style welder i think (on the right).it seems strange to me that the current of the welder pass trough some carbon brushes, especially after noticing on the rheostat a high/low scale that goes up to 300 amps, but the coil on the rotor is composed of 3 coils in parallel, each made with 7 strands of 1mm copper cable with a lenght of almost 2M, basically the whole coil has a resistance of 2 milli ohm, which its too low to be used as a control coil for the generator.at the same time, the id tag says 9KVA, but from my dad experience (a industrial mechanic) a asyncronous motor with the stator as big as the one in the left part of the shaft should be of 4 or 5 KW, so way lower than advertised.basically im confused on what im looking at.i assume that the asynchronous generator can work with some capacitor to make it self-excite (assuming it has some residual magnetization in the core), but im confused on the welder part (if it really is a welder) because internally the coils of the stator of the asyncronous part are connected to the coils of the stator of the welder part, which kinda make sense since i need to create a magnetic field from somewhere for the welder to work, but i feel like that thanks to the slip of the asyncronous part it would create problems down the line.also, again thanks to the slip, i assume there is no way to make the two sides work in parallel to increase the power production on the high voltage side?

author: m k
author_rank: Super Contributor
timestamp: April 15, 2024, 05:03:08 pm
content: Seems to be a slip ring rotor thingy.Both stators are quite black.Maybe it's burned too much.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 15, 2024, 05:52:24 pm
content: Has it a label on it saying made in china or prc by an off chance?.

author: factory
author_rank: Super Contributor
timestamp: April 15, 2024, 08:56:58 pm
content: Quote from: m k on April 15, 2024, 05:03:08 pm220V/380V 3 phase motor and some type of high current generator for arc welding? these are a thing. Is there a spec plate for the generator half?Probably not burned as the armature seems quite clean, probably carbon dust from the brushes, the fan part will help coat everything inside.A slightly different one found on the web;https://weldingweb.com/vbb/threads/579641-Cool-old-Hobart-MP-300-motor-drive-torpedo-welderAnd another;https://psauction.com/item/view/467076/really-older-welding-converter-esab-kb375-with-various-electrodesSeems to be coupled up to an engine, maybe 3 phase mains wasn't available?Putting "ISEA Milano" into a web search finds a lot of welding equipment, some of which is motor generator type, older one shown here;https://www.ebay.it/itm/204446464414David

author: johansen
author_rank: Super Contributor
timestamp: April 15, 2024, 11:38:39 pm
content: Its possible the dc current from the stator's rectifier (where is it?) passes through the rotor slip rings to make the ac equivalent of a DC series wound generator.however i do not believe that's how it works in your case, those brushes do not look anywhere near rated for 300 amps continuous.you may be missing the rectifier and some other parts involved in regulating the current.