218 The N.Z. Journal of Science and Technology. [July 
Fortunately, synchronous motor-generators had been ordered for the 
tramway system which were star-wound, and experiments were immediately 
made to ascertain the effect of ■ arthing the neutral of these synchronous 
motors. The results of these experiments were perfectly satisfactory, and 
it was found that the load could be put on one phase or two phases to earth ; 
and the effect was such as to cause no appreciable change in the delivered 
voltage, whereas when load-transformers only were used connecting the 
phase-lines to an earth used as neutral there was a great variation in voltage 
of the phases. In the extreme case of no load on one phase and equal 
loads on the other two phases we obtained nearly 86 per cent, of the correct 
voltage on the loaded phase, and the unloaded phases gave nearly 173 per 
cent, of the proper voltage. 
The same scheme of obtaining an artificial neutral on a three-phase 
system can be adopted in a 400-volt delta system for light-distribution by 
the use of a star-wound induction motor, by earthing its neutral. The 
regulation, of course, will be governed by the capacity of the motor. 
The A.C. system, it will therefore be seen, lends itself much more simply 
to balance than that of a three-wire D.C. system, if advantage is taken of 
the motor capacities to transfer the energy from one phase to the other. 
An extreme illustration of this was observed during the first few months of 
the Waipori system at Dunedin. One line of the transmission system 
became open-circuited on a pole near the power-house, and was unobserved 
for several hours. The loads at the receiving end remained in balance, due 
to the transfer of energy by the synchronous motor to the other phases of 
the distributing-system. The two sets of transformers at the power-house 
and the receiving end were operated on the two remaining transmitting- 
phases through the ground return. If the older practice had been followed 
as required by the various licenses issued,* in which they require earthing 
to the neutral at one point, and one point only, it would have been impos¬ 
sible to have operated this system with one line open. 
The writer is a strong advocate of the earthing of the neutral of a three- 
phase system, and advises not only the earthing of the neutral at each end, 
but at each point of receiving the energy, and as many other points as may 
be convenient. 
A recent experiment with a small induction motor gave the following 
results :—- 
No-load voltages—A to neutral, 240 ; B to neutral, 240 ; C to 
neutral, 240. 
With 4-38 amp. on A; voltage to neutral—A, 236, i.e., 1-7 per cent, 
down ; B, 244, i.e., 1*7 per cent, up ; C, 240. 
With 4-45 amp. on A and 4-45 amp. on B ; voltage to neutral— 
A, 234, i.e., 2J per cent, down ; B, 240 ; C, 246, i.e., 2J per 
cent. up. 
With equal load of 4-46 loads on A, B, and C, the voltages to neutral 
were—A, 240 ; B, 240 ; C, 240. 
The writer thinks the above may be used advantageously in the solution 
of some of the problems of an unbalanced three-phase distribution, and this 
is his excuse for making such an apparently simple scheme known, as he 
has not seen it published elsewhere. The only precaution to be taken is 
in that of metering, and it will be found impossible to meter on the usual 
power-meters having two elements. A three-element meter or three single¬ 
phase meters must be used. 
* New Zealand Gazette, 25th September, 1913, and 29th Ajml, 1915. 
