Sad, you've got a person updating an otherwise inoperable machine while teaching students a skilled trade while "experts" trash talk. It's hard enough to recruit students into this field even worse when people like you push nostalgic agenda. Sad
Nostalgia has nothing whatever to do with my viewpoint. One reason I work on a thyratron controlled lathe is that I must be one of only a few people left who worked with them when they were new. The first assignment I got when I entered the R&D business in 1955 was to build a temperature control to maintain the correct heat in the damping fluid on a hermetically sealed integrating gyro. The circuit my boss gave me had a thyratron controlling the heater. The damned thing changed firing point with ambient temperature changes and whether there was light on it. I hated it then and nothing has improved my opinion of them since. On my own I designed another control with normal vacuum tubes, which became the standard. Solid state existed then but specialized types like SCRs were not on the horizon.
We have enough spare thyratrons for the Modular I work on that we probably will never go to solid state, but if we run out, I will change.
What we keep trying to tell you is that unless you really know what you are doing, your conversion is not going to be an improvement.
A local shop had a "plant electrician" who left a trail of messes behind when he departed. He had installed VFDs on the wheel and workhead motors on a cylindrical grinder. To start a motor, you pressed the original run button, which lit the VFD, then stepped through the setting on it and used the start and stop buttons on it. When you were done, you had to remember to hit the machine stop button to turn the drive off. Repeat on the other drive. The owner complained that he had to run a seminar every time he wanted to put a man on the machine.
I added additional timers and circuitry to hold the drive on during the braking cycle and ran all the wires through housings or conduit. Then I set up the controls so that the operator only has the original buttons and a knob to set RPM. When it has been off for a certain length of time, it automatically shuts down. The operator can just hit stop and walk away. BTW, your 10EE has a timer with a similar function to turn off the field current after it has had time to brake.
Somewhere back there is an analysis I did on the 3hp DC motors used on the Reliance motor generator units. The designer hit all the bases, multiple windings per slot, brushes offset to make the transition from winding to winding as smooth as possible, etc., a tour de force. The only motors I have worked with that are as smooth are the servo motors that are used on CNC lead screws. I designed and wound a unique three phase magnetic amplifier to run it and had it going, but I am aging faster than the project is progressing, so I don't know if it will be finished. Magamps are also ancient technology but they have some real advantages such as tolerating stalling without damage. They just deliver the rated current and wait for you to shut them off.
Bill
P. S. I found my post about the DC motor-
I was looking at my spare 3 hp 10EE armature and did a little analysis. It has 29 slots with 87 bars on the commutator. Consequently, each slot has three bars connected to its coils. With all the wrappings and poor light where it was, I could not be sure of the exact winding configuration, but it appears to be a lap winding. The brushes are at 90 degree positions, as near as I could measure with Vernier calipers. The brushes are two bars wide so when one bar is centered on a brush, it is contacting the two on either side, lighting up all three coils in that slot. As a three bar set comes up to a brush, first 1, then 2, then 3, the the last 2, then last 1 are energized ramping the field produced in that slot up and down. Meanwhile, as the brush is coming off a set, it is bringing up the next set. The result is a smooth transition from energizing one slot to the next. With the four brushes, the coils are energized four times during a revolution, twice in each polarity since diametrically opposite brushes are + or -. Besides that, the odd number of bars, 87, means that the transition between bars by one brush is shifted by 1/2 bar from the opposite one, blending the steps even more. No wonder the motor can develop strong torque when barely turning and show no discernable cogging.
It seems like every time someone gets a 10EE, his first impulse is to rip out all that obsolete junk and put in a modern something or other. Personally, I am going to keep my DC motor. I may work up a different control system, but the odds on finding a better motor are slim or expensive.
