How did WWII-era submarines control electric motor speed?

[David_Simmons]

Aha. The amplidyne speed control is looking better and better. The propulsion when on the surface was diesel-electric drive. That is, the main diesel engines drove a generator, or generators, that furnished armature current to the screw drive motors. This system is already an amplidyne system since the speed control for it is to vary the field current of the generator. So to use amplidyne control when submerged the only thing needed is to add an electric motor to replace the diesels. Walla! We’re off and running.

[Rick]

@David Simmons

Just so we can see what kind of voltages and currents are involved this site gives the numbers. Scroll down to “The Batteries.”

The US subs had two banks of lead-acid batteries that gave 250 V and a max of 4000 Amp. So the maximum power out of the batteries would be 1 megawatt or 1340 horsepower.

From your link

A total complement of 250 individual cells make up the two banks of batteries each of which can supply 250 volts and 4000 amperes of current.

so if this statement is correct, make that two megawatts.

I have toured the U.S.S. Bowfin in Pearl Harbor. The manunevering room is a tiny corner just forward of the after torpedo room. There were many switches, breakers, and levers that could be thrown on a panel, that was in the center of the room. The back side of this panel IIRC was screened in with a heavy metal mesh (to prevent a salior from rubbing up against some serious amps I’m sure)

Ahh my googlefu is strong tonight. I think I have found the answer! From here

e. The electric propulsion control: includes equipment required for the control and operation of the four main motors when being supplied with power generated by one or more of the main generators or by the storage batteries. The equipment also provides for controlling the charging of the storage batteries by the auxiliary or main generators. Main power cables, capable of carrying the heavy currents involved, connect the storage batteries with the various main generators and motors.

In these circuits, there is control equipment consisting of switches, resistance units, and protective devices designed to permit flexibility of control.…
6C4. Description of main motors. The main motors are of the two-wire, direct-current, compensated compound type with shunt, series, and commutating field windings. Separate excitation for the shut field is provided by the excitation bus which receives power from either battery.Various combinations of armatures in series or in parallel, including all four motors in series for dead slow operation, may be obtained for either surface or submerged operation through the main control cubicle.

Motor speed control is accomplished by controlling the generator speed and shunt field, thus varying the voltage supplied during surface operation, and the motor shunt field when submerged. Reverse operation is accomplished by reversing the direction of the flow of current in the motor armature circuit.

Main motors used in a gear drive installation are classed as high-speed motors and are each rated for continuous duty at approximately 1,375 hp, 415 volts, 2,600 amperes, 1,300 rpm.
6C10. Functions. The control equipment performs the following functions:

1. Start, stop, reverse, and regulate the speed of the main motors for both surface and submerged operation.

2. Provide for series, parallel, or series-parallel connection of the motor armatures.

3. Provide for uniform speed control of the main motors throughout the entire range of propeller speed from about 42 to 219 rpm submerged to about 280 rpm on the surface.

4. Provide for operating the main motors from one or both main storage batteries and from any combination of the main generators.

So there is your answer. There is a bunch more on this site including pictures of the controls and labeling. IANAEE, but it appears that by hooking up one bank of batteries to either two motors or four in series, you get some very slow speeds, by hooking them up in parallel some slightly higher speeds, by doing the same with the second bank of batteries in series or parallel just that many more speeds.

[David_Simmons]

@Rick

From your link
so if this statement is correct, make that two megawatts.

I have toured the U.S.S. Bowfin in Pearl Harbor. The manunevering room is a tiny corner just forward of the after torpedo room. There were many switches, breakers, and levers that could be thrown on a panel, that was in the center of the room. The back side of this panel IIRC was screened in with a heavy metal mesh (to prevent a salior from rubbing up against some serious amps I’m sure)

Ahh my googlefu is strong tonight. I think I have found the answer! From here

So there is your answer. There is a bunch more on this site including pictures of the controls and labeling. IANAEE, but it appears that by hooking up one bank of batteries to either two motors or four in series, you get some very slow speeds, by hooking them up in parallel some slightly higher speeds, by doing the same with the second bank of batteries in series or parallel just that many more speeds.

Yeah. I assumed the battery banks are only used one at a time but it looks like both are used simultaneously.

So they do use field control. This is simplest method and must be adequate to the job. I suspect that fine speed control down to the fraction of a shaft rpm is hardly needed.

Amplidyne speed control would have been so neat and all you need add is a whopping big electric motor. Actually, such a motor might not have taken up much more space than that complex control room, and might have generated less heat. Oh well.