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Hi, I have a Kraftech KT6500W 3 phase 6.5hp genetator ...which isn't actually 6500 watt at all, it's only 2800 va ...being a Chinese copy of a Honda design.
Anyway unaware of this and being a new user of such devises I put too much load on one phase and burnt out that winding on the stator.
Having priced a replacement stator (~£85) and realising 3 phase was totally unacceptable for unbalanced single phase loads, I decided to rewind it as a single phase generator.
Being a mechanical engineer I reversed engineered it and did my research. I then rewound the main power windings based on one of the original phases, this time using copper instead of Aluminium. I knew how many turns for the these windings (~240 turns total) but due to the damage it had sustained I didn't know where the AVR sense voltage tapping was taken. I rewound the exciter winding in the stator too, I was also unsure of how many turns was needed for it (I used 40 turns total based on what was left of the original winding).
Right or wrong it will now actually generate ~240vac (UK standard) no load if I inject about 42vdc using an external supply directly into the rotor brushes. Not having a sense tapping, after a few trials I found a mains to 15v transformer connected off the main windings provided a sense voltage which the AVR was happy with and connecting it to the brushes I could adjust the AVR to provide 240vac no load. Excitation windings I think were giving about 40vac.
My problems really started when I increased the load to 1400w, the output dropped to about 215vac. Voltage on the brushes was surprisingly low too at less than 30vdc??? if I recall it correctly.
Thinking the excitation windings turns were maybe insufficient I've nearly doubled them now to about 70 turns total. They now give 80vac no load but when I connected it to the original AVR it suddenly stopped giving any output for the brushes.
I've since ordered a new generic / universal AVR off eBay (£9.50 inc. p+p) that will accept 60 to 100vac off the excitation windings and 16 to 25vac sense. I've yet to see what this will do when it arrives but anybody reading this ....does all this sound right or will my next AVR go 'pop' too?
Steve
