Class 222
 

Hi

If Class 222 units are deisel-electric, why is it that the desiel engine beneath each coach accelerates when the train leaves a station? In every other desiel-electric unit I know, the deisel engine's role is to produce electricity for the electric motors that do the traction. The desiel engine therefore has no need to accelerate or to slow down.

Any ideas?

Patrick

The only locomotives with electric motors independent of the diesel engine (as battery charger) are the Canadian "GOATS", with battery back-up.
In all the conventional diesel-electrics, as more power is required to pull the train, and the motors suck-up more current from the dc generator or ac alternator, the diesel engine has to account for this. Suffice is to say that various ingenuous methods have been devised for the diesel to electric conversion function, and now digital technologies allow the most straight forward solution of 3-phase alternators - dc rectification - 3-ph.conversion to feed squirrel-cage induction motors.
We might also add that the hybrid Toyota Prius car can be battery operated in the city, but for uphill or motorway usage requires the engine to supply the extra power.
Delighted to answer any technical question.
Cheers from Dario

Hi Dario

What you say is very interesting. However, my experience of French diesel-electric locos (mostly CC72000 and BB67x00 series) is that the diesel engine stays at a constant speed no matter what te loco does. Anybody care to coment on those locos?

Patrick

In that case I assume that the diesel engine will always be running at about 1000 rpm even when stationary. Doesn't that make them very noisy in stations etc?
John.

I have gone reading through my Electric Traction books for more details.
DE locos are designed to operate at rated power, i.e. with engines running at rated rpm speed, to match the generator characteristic curve. Then the electric motors' speed is controlled by the engineman for proper traction.

Hi swisstrains

They are quite noisy and polute the atmosphere quite a bit. This is why, on the line Paris (Gare de l'Est) to Troyes and eastwards, trains are brought out of Paris by an electric engine and then this is swapped for a deisel CC72000 series for the rest of the journey. Apparently, residents from Paris and the Eastern suburbs complained to SNCF.

Regards

Patrick