Does anyone know how the control stand communicates with the governor and visa versa (voltage), and what voltage (and is it just binary?) is sent into the 27-pin MU connector to communicate information to the other or multiple units.

Is the auxiliary generator the power for the; control stand, governor, battery charge, and every other; dial, gauge, and circuit (except for the main traction generator and traction motor system)?

I'm wondering how that simple PG governor controls just about everything and how it gets its power and sends feedback to the control stand and how the control stand is powered.

74 volts is the standard operating voltage in most diesel electric locomotives. Simplified diagram is from a GP9 locomotive. AV, BV, CV & DV coils are the speed control solenoids within the governor; AV, BV, CV, & DV switches are the throttle switches in the control stand. There are a few other wires controlling Overiding solenoid and low oil pressure etc. with in the governor that are not shown. Every voltage going to the governor would also go to the MU cable. No feedback to the control stand is necessary in these earlier locomotives. The governor has the ability to back off the excitation if it can not maintain engine RPM via hydraulic lines going to the vane motor of the load regulator, this can also by done electrically via the overiding solenoid. The dot sequence diagram shows what connections are made in what throttle positions.

Some of the other items shown on the diagram:
30A- Control circuit circuit breaker
Gen Fld switch-controls power to the generator field relay, when open, locomotive can not develop power to move.
Engine run switch- controls the power to the governor solenoids via the engine run relay
PCS-pneumatic control switch- function is to open engine run circuit via PCR coil/relay and drop engine speed to idle in the event of a safety related pneumatic event such as deadman foot pedal activation or emergency brake application.
IS-isolation switch-used to take a locomotive offline so it receives no excitation or engine speed signals from the control stand or MU cables
NVR-No Voltage Relay-function is to open engine run circuit and drop engine speed to idle if the power to the engine cooling and traction motor blower circuits fails.
GR-Ground relay-function is to open engine run circuit and drop engine speed to idle in the event of a fault from the traction generator circuit is detected.
PC wire-Positive (+) control wire

Yes, the aux gen supplies the power for control, lighting, and battery charging. Most 1st and 2nd generation EMD road locomotives would also have a D14 companion alternator attached to the front of the main generator to supply AC 3 phase variable voltage and frequency power to the cooling fans and traction motor blower motors ( their speed is directly related to engine RPM).

For more information see George Ellwood's excellent site:
http://www.rr-fallenflags.org/manual/manual.html
Please consider a donation to maintain this helpful site and keep it growing. I recommend the EMD GP9 manual for beginners and use it in my basic locomotive classes. Hope this helps, feel free to ask more questions if needed.
Mike Tillger

Worth noting that the battery is nominal 64 volts. With the engine running, the system voltage is maintained around 74 volts as that is the charging voltage for a 32 cell 64 volt lead-acid battery. Apply 74 volts and a discharged battery will soak up lots of current (generator has to work harder to maintain the voltage) and current flow reduces as the battery charges until it's just a comparative trickle to a fully charged battery.

Just as most people think of their auto's electrical system as being 12 volts when it's really closer to 14 (give or take a few tenths) when the engine is running.

Steve

Go back to the interurban days that preceded the diesels in MUing, controllers were just large rotary switches cutting relays with resistors in/out shifting motors from series to parallel for speed changes. Easily could just use the line voltage to do this.

Note the North Shore electroliner's cooking grille is heated by the power resistors, your electroburgers really are..."electro"

To add just a little to what filmteknik was saying: the float voltage has to account for the internal resistance and self-discharge of the battery, so it's higher than the chemical potential alone (about 2.15V per cell, or 68.8V for two 36-volt strings or monoblocks) would indicate.

"Average" temperature float voltage for a modern VRLA pair is between 2.23 and 2.27 Vpc, with 2.25 as the average, and this (not coincidentally) is 72VDC. The actual voltage provided from the aux gen will be a little higher to cover losses in the supply wiring and voltage regulator -- for example, in the MP36 the auxiliary alternator runs at 55VAC 3ph and rectifies to 74VDC, 18kW peak).


But you were asking about control: a reference is AAR standard S512 for MU control; another is APTA RP-E-017-99, and isn't it convenient you can download your own copy of the latter here:

http://www.aptastandards.com/portals/0/ ... Hauled.pdf

All the 'binary' (meaning e.g. relay-switched via on-off voltage presence) is 74V. You may note that the 'loadmeter' connections have an analog range specified in mA, with no fixed voltage specified.

Electric Railways of every mode did not use line voltage for MU control. The control units and controllers used a 32VDC circuit cabled between cars for control. In the cases I am familiar with, dropping resistors were used to achieve this, with no batteries involved.

Incorrect sir....please allow me to explain.

While the Electroliner stove was electrically powered, it was most definitely NOT from waste heat from the acceleration grids.

The stove worked off AC power, provided by one of the train's motor-generator sets, and heated the pans inductively.

Waste heat from the acceleration grids would only be available during, or shortly thereafter acceleration, and on a run with limited stops (like Chicago to Milwaukee in 90 minutes...), would not be available for most of the run.

An example of waste resistor (acceleration ,and dynamic braking) heat put to good use would be the PCC car, which DID utilize this waste heat for passenger compartment heating. Additionally, the frequent starts and stops of city streetcar type operation would provide more heating than a high speed, limited stop service.

Jeff

I'll have to reread some of the info I have, thanx for the correction.
IE CERA book...duh...