Re: 8 car C set

[Michael <mk@netstra.com.au>]

I believe, but I could be wrong that a chopper control is based on a 
thyristor, a semi-conductor used to vary voltage.

The characteristics of the chopper control are such, that power changes can 
be delivered a lot smoother than that of a resistance grid. Those in 
Melbourne would certainly know what it feels like when taking off in most 
of our trains, that you jolt. If you are in Melbourne and happen to see the 
Comeng M cars 691-698, they are chopper controlled. When taking off they 
feel quite smooth, though could be a lot smoother, owing to the pairing M 
car still containing resistance grids.

I believe that chopper controls are also a lot more efficient when it comes 
to power consumption.

Finally, I have noticed that the chopper controls emit a single, high pitch 
whine when a train is powering, I am not sure if this comes directly from 
the chopper circuit, or it's an interferance that's being picked up by the 
speakers (You can hear it from the roof on the Comengs). Perhaps someone 
can answer this. 

Maybe someone has a link that explains a lot more about chopper control :-)

Regards
Michael

p.s. Melbourne's one and only 4D set is naturally, chopper controlled, as 
with sydney's comengs. The whine on them sounds so much nicer too :-)

Jonathan Boles said on 28-Oct-1999 in <01bf20e1$109b3200$b90065cb@tom-
boles>:

>is a chopper some kind of variable resistor?
>> ..."chopper" electrical circut
>
>

-- 
Michael Kurkowski
Ph: 0416-044-124
Web: http://www.netstra.com.au/~mk

"The cheque's in the mail..."