Monarch 10EE and VFD conversion

Same day I arrive after driving cross country. One of Murphy's corollaries,

"Odds are when you find a great deal on something you need or want, it's far enough away or too expensive to ship to net any savings"

I'm not sure I even have the power available to run a 10hp spindle...

5hp, is no problem, 7.5, probably. 10hp, might need to do some rewiring. Unless programming the inverter for a second or two of ramp-up would keep the motor from drawing the usual inrush spike?

Jon

Yeah, I think I could manage that... And, that would give me some Monarch parts to sell that might offset the motor and VFD somewhat...

Jon

2 seconds spin up time == no inrush

Ok, I could do 30 amps. I have 50 amps single phase available in total, with my rotary phase converter coming off that circuit with 30 fuses in the disconnect. I know I don't use all that, so wouldn't have much concern over pulling 25-30 amps for the lathe.

So, is a motor's inrush draw rate for full load, no load, or some percentage load? This is good stuff to know even if I end up with something else.

Jon

Hey Iggy,

For starter's, why?? What's wrong with the as-designed method of supplying the DC voltage to the spindle motor rotor and field from the same source (in this case, an MG set)? Why two?

Probably not that it can't be done, but safety would dictate a lot of control circuitry so that the motor can't over-speed because of the loss of field excitation. Bad news on a lathe if it were to happen. The motor would probably fly apart within a few seconds, but imagine the chuck and work-piece speeds for that second or so. If you've never seen it happen, it's hard to imagine.

Take care.

Brian Lawson, Bothwell, Ontario.

Ive been recently told that Monarch is making a new batch of 10EEs, but all the machines have been spoken for..primarily the US government

And they are selling for $125,000

Gunner

Just fire up your mill first and let it run, and it adds to the capacity of the RPC

Gunner

I don't see why not. That's certainly how the off-the-shelf controllers operate, with an optional field winding supply.

I don't know about this particular DC motor, but in general DC motors with separate field windings can be wired in parallel or series and run off a single power supply, with varying torque-vs-speed characteristics for those two configurations.

It's the inrush draw on top of a couple other machines running that I was concerned about, not RPC capacity. With everything running right now, I total 9.5hp, but 5hp is the biggest motor, and it starts just fine off a 3hp RPC. I'd assume a 10hp motor is going to have at least double the inrush of a 5hp motor.

Jon

Im running 7.5 hp Clausing on my 5hp rotary with no issues

Gunner

Well again, it's not RPC capacity I'm worried about, it's the inrush current that concerned me. If I really need a bigger converter, one of my customers has a 10hp commercial RPC he's offered me for free. But if it's going to pop the breaker every time I light it off.

Sorta like the air compressor I bought a couple years ago at an estate sale. Bought and paid for it, and they let me strip the disconnect box off the wall. I was aghast when I found 60 amp fuses inside! My whole house only has 100 amp service. But that's the max inrush. It'll pop 20 amp fuses, but has been running 3 years now on 20 amp slo-blow fuses.

Much as I might like to go look and seriously consider it, I've decided the Monarch is not for me. I need something I can bring in, level out, plug in, and run...

Jon

It can. All you need is two power supplies of the right voltage and current. All of that is produced by the generator in the early ones, and by the electronics in the later ones. Most people don't have variable power supplies of the proper ratings on hand. (And no, I don't know what the proper ratings are. :-)

Enjoy, DoN.

The 10EE separately varies the rotor and field at different times to achieve the various speeds. Think two variable resistors (probably set up as rheostats in the early M/G types, and as potentiometers in the later electronic types. The rotor is increased until you reach a maximum voltage -- and then to continue increasing the speed, the field current is decreased.

The separate variation si why not a single power supply. No wiring in either parallel or series in this case.

Enjoy, DoN.

So, then, there is no real need to change to a 3 phase motor and VFD, all one needs is to make or buy a proper set of power supplies? That seems far easier than making all those shaft and mount adaptors and much more straightforward.

I made a power supply for my mill and it was completely trivial. It was not adjustable or regulated, though, but I do not think that it needs to be regulated. Adjustability, may be a bit tricky, but not totally impossible with a multitap transformer or something like that.

i

I've heard it said they named the Monarch the 10EE because that's how many EEs it takes to maintain one.

Karl

The speed and torque characteristics may have been varied that way by the original antique controls, but that doesn't mean it is the only way to run that motor. One might, for example, apply a fixed field current and have it act as a permanent magnet motor, which is quite suitable for this type of application and horsepower. Such a power supply is easy nowadays with solid state rectifiers, versus when it was all new.

Multi-KW variacs show up on eBay all the time with little buyer interest (read: cheap). Typically surplus from theater lighting systems.

Starting a 10 Hp motor right off the mains, especially with a heavy lathe chuck on the high-speed range, will really dip your power, if running off wimpy single-phase power. However, starting the same motor off a VFD won't make the slightest flicker in the lights. The VFDs have soft-start, and you can set the start ramp time to your liking. Even a fraction of a second ramp-up reduces the surge by a huge factor.

Jon

The problem there is you lose the torque that the DC motor could provide in its lowest range. DC motors generally have a much wider speed-torque range than induction motors, and the special motor on the EE was designed to extend that as far as possible. That's how they got away without having a back gear. If the DC drive can be fixed relatively easily, I'd do that. If either the motor or generator are shot, then it would be REALLY expensive to fix, like a rewind. But, that is fairly unlikely. It is much more likely to be bad brushes, dirty rheostat or relay contacts or something like that.

Jon

I actually measured the starting current of a 10 HP motor.

Mine, starts very nicely from just 180 uF capacitance on one leg (run caps only).

At the starting moment, the motor draws 120 amps.

In fact what VFDs do not have is hard start. So a VFD may not be able to start the worst loads, like a crusher or a big conveyor. A lathe, though, is not a hard starting load.

i