The Zena welder-generator

This one is for the technically minded people. Others can skip!

Back in 2010, we discovered that our barge's alternator was totally unsuitable, barely able to sustain the boat's batteries even when motoring. This is because someone fitted an alternator designed for a high speed engine to our low speed engine. We rectified this in 2011 with an alternator that they use on the American yellow school buses.

We also built a generator unit in the garage at home in Sydney and shipped it over to France. Heart of this generator was a 1 cylinder diesel engine, driving a US built Zena welder-alternator. This impressive unit is either a 200amp welder or a 200amp battery charger, at the flick of a switch. In the early years, we used the welder quite a bit making things (such as bike racks) and also for repairs in all sorts of areas. For battery charging, the Zena is impressive and can quickly recharge our very large AGM battery bank in about 45minutes.

All went well with the Zena until 2014 when it stopped working. Basically, it is a rewound alternator originally designed for a small truck. Zena add a second set of diode rectifiers and beef up the windings. However, we discovered that there really is not enough air flow and the configuration/connection of the extra diode rectifier is not electronically correct, leading to unbalanced heating of the diodes. They added a false back to the alternator to house the second set of diodes. There were also problems with internal nuts working loose and poor soldering. These would not normally be a problem, but our one cylinder engine does vibrate a lot and things have to be perfect to survive well.

So, this year, I rewound the alternator stator with very high quality, high-temperature wire and removed the diode rectifiers. I built a new rectifier box with big copper bus-bars and new high powered diodes. The box has two fans that turn on one by one as the temperature increases. Everything is interconnected by much bigger wires and large brass nuts and bolts.
Rewound Stator with special wire, nomex insulation and new three phase connections
Unfortunately, everything worked really well except that the small wires leading into the rectifier diodes fractured due to the vibration because I mounted the rectifier box onto the engine frame. Even strengthening the wiring was unsuccessful with the diodes fracturing again after a relatively short time.
Rectifier box with fans, copper bussbars and original fragile diodes
So, I was able to obtain some much more rugged diodes here in France and mount them on the copper bus-bars. I also moved the rectifier box to the side of the generator box-cover which has far less vibration. Either solution would have been okay but both together should be more than enough.
New rectifier box
We have now run the whole new arrangement for many hours with no troubles. The alternator winding are 100degrees cooler than before and the alternator diodes are also more than 100degrees cooler with the second fan never coming on. Also, we are getting more amps out of the generator.

So overall, a big success which should continue to give trouble-free service for years to come.

Best Regards,
Dave