So, how does an M-1 work?

In answering the question posed in another thread, I felt we should make a new thread on this.
The question is, "How does propulsion work?"

Let's start with the M1 and M3

These cars' propulsion is "switched resistance" DC traction motor propulsion.

We need three prerequisites before we can consider moving this massive chunk of steel.
1) If we start this thing up, can we stop it?
This is ensured by requiring a at least a minimum amont of brake pipe pressure (80# for M-1...110# with M-3s in consist). This amount of brake pipe pressure will energize all the ERs (Emergency Relays) in the train. Since Door Light, P-wire, and local propulsion are interlocked through the ERs, the train is not going anywhere without them energized.

2) I don't want to draw power in the train if my doors are not closed.
This is accomplished by a series trainline circuit that passes through all the SLRs (Signal Light Relays) in the train, and energizes PIR (Power Interlock Relay) and the Door Light. If you see a red door open indicator light on in any vestibule in the train, the Engineer should not have a door light. (Unless he's in Door Bypass).

3) I don't want to draw power if any car is holding brake, or a hand brake is applied.
Ensured by another series circuit that checks that all brakes are released. PKO (Power KnockOut) will energize, and the Engineer will get a trainline "release" light, if all brakes are released.

If we have all of those 3 conditions met, the Engineer can go ahead and generate propulsion trainlines.
Each car reacts to the propulsion trainlines.
The propulsion sequence is the same, whether the Engineer goes to P1 or P2, P3, or P4. The only thing that changes is a higher acceleration rate is called for if he goes beyond P1. He will get a P2 rate if he moves beyond P1 on the controller handle. (P3 acceleration rate has been disconnected for years because of substation issues) Let's assume the Engineer has moved the handle to P4.
First, the traction motors are made up in a series circuit, by Line, Series, and Ground contactors energizing. Resistance is then gradually cut out, step by step, by the KM controller. The rate at which the resistance is cut out is controlled by rate control and current limit circuitry. Load weigh is also factored in to adjust the amperage allowed. All the propulsion and braking resistors are in the large cages you see on either side of the car, rearward of the first set of doors.
When the car has sequenced up to full series, it will transition to parallel configuration. This is considered P2. The "F" end and "B" end trucks are now in parallel with each other. Series contactor deenergizes and PK and PM (Parallel K and Parallel M) contactors energize. This allows the train to accelerate more, as the KM controller runs backward and cuts out more resistance, step by step, from the parallel circuits. When the KM controller gets to position 13 of parallel. It stops. You're in full parallel, and that's all you get out of that.
P3 and P4 are what's called "weak field" modes. By shunting the traction motor fields, you get more current through the armatures of the motors.
That shunting is added to the full parallel mode that you're already in.

For dynamic brake, all the power contactors will be deenergized, and the high voltage switchgear is isolated from 3rd rail and ground. Braking contactors BK, BB, and BM energized and make 2 closed loops. The motors are now generators, and braking effect is attained by changing the resistance in the circuit with current limit circuitry again.

[see next post]

http://www.L773.com/M1prophvckt.jpg 603k jpeg

This is what the M-1 high voltage propulsion circuitry looks like electrically. I have a better print at work...had to chop off the ends of this one to fit in scanner. I don't think GE will get too mad at me for posting it, as DC propulsion is passe.

[see next post]

For the M-7 propulsion, we want the same 3 prerequisites as for the M-1 and M-3.

However, the actual propulsion in the M-7 is a totally different animal, as it is AC propulsion.
The 750 VDC charges up filter capacitors known as a DC Link. Devices called IGBTs (Insulated Gate Bipolar Transistors) are capable of switching high currents from this DC Link very rapidly. Using what's called PWM (Pulse Width Modulation), The computer fires these IGBTs as required to produce what the traction motors will consider three phase AC power. The frequency and/or voltage are changed as required for torque, acceleration, and deceleration by dynamic brake. The M-7 resistor grids are only needed for dynamic brake, as the LIRR substations are not equipped for regenerative braking. The M-7s are pre-wired for regen. All that would have to be done is install the LB12 contactor, and hook up the wires that are now deadended. And install the switch in the Engineer's cab.
There are no resistors needed for propulsion mode.
In the M-7, there are 2 propulsion inverters per car. One does the 2 motors on the "F" end truck. The other does the 2 motors on the "B" end truck.
I won't post any schematics of the M-7, as that is current technology and intellectual property.

In reading the print posted above, you can pick out the contactor tips mentioned.
The 1,2,3,4 in the circles represents the traction motor armatures.
The stuff by where it says Rev 1, Rev 2, etc. is the reverser tips. The little squigglies by where it says FF or F is the motor fields. If the reverser throws the other way, the current flow in the fields is reversed, and the motor will turn in the opposite direction. You only reverse the flow in either the fields or the armaures, not both. If you do both, the motor would turn in the original direction.
The stuff in the middle of the print, under wher it says "propulsion",
is the cam operated contactors, that short out resistance from the circuit as the controller advances. Off to the left, you also have additional cam operated contactors, that are only used in series operation.

I hope this all helps. Anything else, ask!

Tom

Oops. Forgot to mention there are no propulsion trainlines such as series or parallel command in the M-7.
Amount of traction called for is monitored by P-wire. Unlike the M-1 and M-3, where P-wire is only monitored for braking. The M-7 monitors P-wire for propulsion and braking.

Tom

<i>I won't post any schematics of the M-7, as that is current technology and intellectual property.</i>

Ahhh, AC inverters are all kinda the same and boring, too

So, on the M-1s - they only use the P2 rate, now? What is that rate anyway (amps and in mph/s)

N3, here's a question --

In troubleshooting M1/M3 stuff on the road, we classically loop the P-Wire to isolate problem cars that will not release. We then cut out the trucks or the E/P's in the trouble cars and away we go.

Now, this is the first time I'm hearing that M-7 P-Wire also controlls propulsion. They don't tell us Transportation guys those things.

Exactly how is this done? An oldtimer would say polarity is reversed, but that would be far too simple. What kind of voltage gives say, Max Brake vs. Full parallel?

It would also then be safe to sat that looping a P-Wire in an M-7 would affect propulsion as well as brake. True?

From an "on the road" troubleshooting point of view, please fill me in on this.

Thanks.

Clem

Clemuel,

The M-7 does use P-wire for amount of traction requested as well as for braking. I do not have a duplicate propulsion manual at home, so I have to get the values for M-7. They range from 100 to 500 milliamps. The values are totally different from M1/M3 P-wire. Those readings are:

Coast 500 ma (M-3 550 ma)
Inshot circa 430 ma
Min Brake circa 370 ma
linearity to max brake
In Max Brake a switch opens to completely open the P-wire circuit.

The M-7 will use a value from 100ma to xxx for brake call
let's say xxx is coast
then xxx to 500ma would be power range.

I'll get the M-7 figures when I go back to work. I've been off since Saturday

To hazard a guess as to your excellent point:

There are trainlines still used in the M-7.
I just wanted to differentiate between the M1/M3 propulsion commands of trainlines 3 (P1), 4 (P2), 5 (Brake), and 6 and 7 (weak field commands).
These are not needed because there is no series, parallel, or weak field in AC propulsion of M-7.
There are trainlines such as Power Enable, Traction Interlock, Forward, Reverse, etc.
If the computers saw that power was being called for, but couldn't tell how much power (from P-wire), it would probably default to a low acceleration rate. To loop a P-wire in an M-7, though, I believe you would have to activate the drum switch to "Isolate", which would put any cars beyond that point just along for the ride, anyway. (Cut out SBCOs?)
Transportation people probably know about that better than me, since we only deal with single pairs in the shop. (I'm considering bidding a Road Car Electrician job, if a good one comes up. Then I would be exposed to multiple pair consist troubleshooting on the 7s) Most of that kind of stuff we're just gonna have to learn on the fly, unfortunately. Like they did with the M-1...and like we did with the differences in the M-3...and like we are doing with CCM M-1, and inverters in M-1 and M-3, and Microcab ATCs. Get the picture here?

Phil,
There are two rates used.
Controller handle to P1 gives P1 rate
Controller handle to P2, P3, or P4 gives P2 rate
Controller handle to P3 or P4 would have given P3 rate, but that has been disabled with low rate jumpers. (This place is just no fun) Maximum acceleration rate used for M-1 and M-3 is P2 rate....sorry!
I've forgotten the figures you requested. P1 amperage progress point is I think around 288 amps, P2 rate I think is 350 - 375 amp range? [edit: it's 377] I have to find the figs.

Clemuel,

Here's the values for M-7 P-wire (all values in milliamps):

Emergency Brake 94 - 106
Max Brake 124 - 140
Min Brake 256 - 277
Coast 290 - 310
Min Power 323 - 343
Max Power 495 - 515

(linearity between min and max brake, and min and max power positions)

The Emergency Brake and Max Brake values do not make it into P-wire trainline loop. They are shunted back to the panel through FSR (Full Service Brake Relay) and are simply for the Event Recorder to record Master Controller position.

Tom