I have managed to get hold of a 3 phase STC 7.5 kW alternator. Unfortunately the manual is in "Chinglish". I guess the original Chinese characters have been put through an automatic translator. Below is a portion of the Chinglish text - concerning the wiring diagram and harmonic / elementary wave / excitation coils.
Whilst I think I can get the gist of the text, I am not sure I really understand what is being said. I wondered if any of you good fellows may be up to the challenge and see if you can put it into a more understandable form of English ?
My queries are....
1. What is an elemantary wave coil and what does it do ?
2. Why have THREE harmonic windings feeding ONE field coil ?
3. Why is only ONE of the harmonic coils connected to the "elemantary wave coils" ?
4. Why / how does the elementary wave coil only effect the UNLOADED voltage ?
5. Why have elemantary wave coils when there is a "field rheostat" fitted which should adjust the output voltage ?
Here is the Chinglish text...
The wiring principle chart is shown as in Fig 1.
In the diagram the Z4 Z5 and Z6 Z7 as for the elementary wave coil of the auxiliary winding of the difference turns. Both can reach to adjust unloaded voltage purpose vis change over right and reverses series connecting plate. The unloaded voltage rises when the Z4 Z6 connect to the Z7-Z8 . When the Z4 Z7 connect to the z6 z8 the unloaded voltage goes down. When the z4 connect to the z8 or the z6 z7 connect to the z5 z8 that the two elemenbeve wave coil will be used separately. The connecting plate has been connected afotre delivering. According to the needs of the users it can be changed to connect elementary coil as above method.
STC-3KW-20KW STC-30KW -50KW
Fig 1 wiring principle chart
1. Main winding 2. Harmonic coil of the auxiliary
3. Field rheostat 4. Elementary wave coil of the auxiliary winding
5. Silicon-controlled rectifier 6. Excitation winding
7. Winding of indicator 8. lndicator 9. Voltmeter
Regards,
Ian