102 fan
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I'm a bit confused about the M/A set in an aircon MKII. Why does the ETH have to go to an electric motor to turn an alternator? Why not just use some form of transformer?
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Mk ii m/a
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swt_passenger
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DC to AC conversion possibly.
They couldn't use Inverters, so that's what you'd have to do to use AC equipment.
They couldn't use Inverters, so that's what you'd have to do to use AC equipment.
Smudger105e
Member
That's exactly why there's an MA, to 'transform' the voltage. An ETH supply is not always wobbly electric? The MA's on the Mk2f's on the GatEx were run off DC too, so a transformer would not be of any use...
Also, the ETH or ETS supply voltage can vary depending on the load, how many vehicles are in the formation etc. By powering an alternator set you can have consistant control over the on board electrical supply, which is vital for something like air conditioning equipment.
ChrisCooper
Established Member
I think the aircon is 415v 3 phase too, so can't run directly off the locos train supply (unless it's a HST powercar which do produce 415v 3phase). As has been said the MA also helps to maintain a constant voltage whilst the train supply can vary.
Nym
Established Member
Motor Alternators where frequently used before the advent of large scale power electronics in the last 10 years.
DC-AC conversion is possible using many power electronics, but these are expensive.
Motor / Alternator sets can have a small amount of control gear and a flywheel to enable a nice smooth 3 phase supply, as DC Motors can produce constant torque (witch is whats needed for a 3 phase syncronous machine (That i suspect the generator is), and if this starts to lag slightly, it will affect the slip within the syncronous machine, that can be detected and more torque demanded of the DC Motor.
DC-AC conversion is possible using many power electronics, but these are expensive.
Motor / Alternator sets can have a small amount of control gear and a flywheel to enable a nice smooth 3 phase supply, as DC Motors can produce constant torque (witch is whats needed for a 3 phase syncronous machine (That i suspect the generator is), and if this starts to lag slightly, it will affect the slip within the syncronous machine, that can be detected and more torque demanded of the DC Motor.
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