Class 309 (and other EMUs) peak power

[Justin Smith]

I believe a class 309 Clacton EMU has a total quoted power of about 1120hp per 4 car set but can (could) comfortably do 100mph.
Elec locos usually quote both peak and continuous power with the latter being the default level, e.g. a class 86/2 would be 4040hp continuous and 6100hp maximum (is this the one hour rating or is that less ? )
Am I right to assume that the 1120hp stated for the class 309 is continuous power ?
And if so what is its peak power ? And if it's, say, plus 50%, would that approximation also apply to other EMUs ?
This makes a big difference to calculated hp/ton figures, esp as trains do not have to use peak power all the time, just when ascending gradients or during full acceleration for instance.

 

[Snow1964]

I have a vague recollection that on the EMUs of late 150s and early 1960s peak power was about 15% over nominal rating. The multiple windings on the motor effectively created a magnetic field which limited the rotation of the motor, in later years some of the 4CEPs had extra field weakening notch (think they were nicknamed greyhounds) to allow them to run faster

The 1960s ac locos had 3 ratings, continuous, 1 hour, and peak (5 minutes), the 5 minute one is your short burst of power that gives the max. Ultimately it was how hot you were prepared to let it get without burning out any wiring insulation and electrical components. Because there were multiple classes of electric loco all with different ratings the amp meters were painted with red yellow and green sectors so drivers didn't need to remember the numbers.

 

[Justin Smith]

I have a vague recollection that on the EMUs of late 150s and early 1960s peak power was about 15% over nominal rating. The multiple windings on the motor effectively created a magnetic field which limited the rotation of the motor, in later years some of the 4CEPs had extra field weakening notch (think they were nicknamed greyhounds) to allow them to run faster

The 1960s ac locos had 3 ratings, continuous, 1 hour, and peak (5 minutes), the 5 minute one is your short burst of power that gives the max. Ultimately it was how hot you were prepared to let it get without burning out any wiring insulation and electrical components. Because there were multiple classes of electric loco all with different ratings the amp meters were painted with red yellow and green sectors so drivers didn't need to remember the numbers.

Thanks for that.
Was (is ?) that 15% for 5 minutes or 1 hour ?

 

[contrex]

The 1960s ac locos had 3 ratings, continuous, 1 hour, and peak (5 minutes), the 5 minute one is your short burst of power that gives the max. Ultimately it was how hot you were prepared to let it get without burning out any wiring insulation and electrical components.

I think the ratings times are worked out to provide acceptable maintenance/rewind intervals. If you took the 5 minute power for 10 minutes I don't think the loco would burst into flames

 

[Strathclyder]

I have a vague recollection that on the EMUs of late 150s and early 1960s peak power was about 15% over nominal rating. The multiple windings on the motor effectively created a magnetic field which limited the rotation of the motor, in later years some of the 4CEPs had extra field weakening notch (think they were nicknamed greyhounds) to allow them to run faster.

Some CIGs were also similarly modified. South West Trains ended up with the bulk of them upon privitisation IIRC and created a further 8 Greyhounds with the buffet vehicle being swapped out for a CEP trailer. @nw1 will likely know more though, as slam-door 3rd rail EMUs are something of a blindspot for me lol

 

[nw1]

Some CIGs were also similarly modified. South West Trains ended up with the bulk of them upon privitisation IIRC and created a further 8 Greyhounds with the buffet vehicle being swapped out for a CEP trailer. @nw1 will likely know more though, as slam-door 3rd rail EMUs are something of a blindspot for me lol

I'm not so good on the exact technicalities of how the acceleration works but do remember the Greyhounds and when they came in.

The introduction was at the 1989 May timetable, when the Portsmouth Direct fasts were accelerated thanks to the introduction of Greyhounds. The initial batch was 1301-1312, IIRC, but later, more were introduced.

Initially they were found only on Portsmouth fasts however by May 1991 they also operated the majority of Portsmouth via Eastleigh too, which partly interworked with the Portsmouth fasts (in some hours, a 12 car from the Direct arriving at Portsmouth Harbour would divide with front 8 returning up the Direct and rear 4 going via Eastleigh).

I believe, but might be wrong, that the Greyhounds did not work the Portsmouth via Eastleigh on electrification in 1990, however.

Eventually Greyhounds also started appearing on other services such as those Southampton or Poole semi-fasts not operated by 442s when the frequency on the SWML increased later in the 90s. I do vaguely remember the CEP trailer units but I think these were much later on (certainly later than 1997).

 

[hexagon789]

The 412s had the additional motor field weakening stage added in 1988 as well.

Normal stages are at 31 and 38mph; on the 'Greyhounds' an additional stage comes in at 45mph - improving acceleration between 45 and 60mph and increasing the unit balancing speed to over 90mph on level track.