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Help design a DC motor drive for the 10EE

Kezorm

Plastic
Joined
Mar 15, 2016
I'm in the process of developing a new drive for my '43 round-dial 10EE. Modern electronics with PFC (Power Factor Correction) input stage and full-bridge IGBT output stage. This means a reversible DC motor drive capable of full armature voltage, field weakening, closed loop speed control, etc. Designed for 230VAC single-phase input, although it will actually be able to run as low as 85VAC at reduced output power. Output is designed specifically with the 10EE 3 and 5HP motors in mind, although it will also be capable of driving 3-phase motors. Clean DC output (high frequency switching of DC bus), not the chopped up AC of the cheapy SCR drives. The initial design won't be regenerative, but it will incorporate control of a braking resistor. Not going to be cheap - I estimate bill of material costs will end up around $1500. But, it keeps the original DC motor and backgear vs. spending money on a VFD conversion or the like.

So, here's where I need help... What inputs / outputs does the drive need? Think ideal world, not necessarily limited to only direct retrofit of a 10EE. Here's what I have so far:
  • Forward switch
  • Reverse switch
  • Left carriage travel limit switch
  • Right carriage travel limit switch
  • Left ELSR Switch (ELSR-like function without the need for the actual ELSR mechanical bits)
  • Right ELSR Switch
  • Primary Speed Control Potentiometer
  • Secondary Speed Control Potentiometer for rapid reverse
  • Output to drive contactor for braking resistor
  • Encoder input for closed loop speed control

I'm sure I'm forgetting something or not aware of some functionality on the newer machines...

Note that this entire effort is open-source hardware and software. I would welcome anyone who wants to contribute to the effort at any level (time and knowledge, not $$$). So far, I have all of the power design complete and am working on the final "logic" board that will have all the smarts and interface I/O - thus the question on I/O needs.

To the same point, anyone is welcome to build their own drive from this design. Obviously the design is not yet complete and documentation is seriously lacking, but what is there (and what will be there) is free for anyone to use or modify for their own purpose. In fact, I would love if I could get a few more people to buy into building one of these drives for themselves. I've ordered 5 each of all the PCBs, so it would be nice if I could recoup some of that cost. If demand is there, I would even consider coordinating a group order / build. Component costs often come down significantly when buying more than 1.

I'll work up some more info if anyone wants to get involved in the design at a lower level. Here are a few links to the circuit design so far. All untested at this point, but I do have boards and parts on order for the first unit.

Input stage power board (essentially a 380VDC, 4800W DC power supply)
CircuitMaker: MonarchDC - Power

Input stage logic board
CircuitMaker: MonarchDC - Logic

Output stage power board
CircuitMaker: MonarchMotor - Power

Thanks!
Greg
 
Since you have competition in the Beel drive ( thats already out there and has experienced that every 10EE can be different ) It seems foolish to spend 1500 in materials for something you can buy relatively economically.
 
Since you have competition in the Beel drive ( thats already out there and has experienced that every 10EE can be different ) It seems foolish to spend 1500 in materials for something you can buy relatively economically.

The open source nature of this project suggests it can be developed and repaired for years to come. Is the Beel drive proprietary? If so then future support may be a challenge.
 
Since you have competition in the Beel drive ( thats already out there and has experienced that every 10EE can be different ) It seems foolish to spend 1500 in materials for something you can buy relatively economically.

To put numbers to that... authorized-channel, brand-new, with-warranty - turnkey and 'approved' - Parker-SSD 514C-16 4Q DC Drives sell off-the-shelf for not that much above your $1,500 raw BOM cost.

Used-but-good Eurotherm/Parker-SSD 514C-16 go for around $300-$400. Two of my three were NIB/NOS at that price and the allegedly 'used' one electrically pristine as well. Minor cosmetic scars only.

Add another $100 for a used 5xx series that can be 'slaved' to the 514C for Field regulation.

One knob control under the hand thereafter.

Under 200 RPM, it appreciates the Lenze smoothing filter.

Above 200 RPM it may as well be Elliot Roosevelt. It just "doesn't give a damn".


Bill
 
You might consider adding a radius encoder input (i.e. cross feed), which would enable constant surface speed control. Also it would be nice if the desired fwd & rev. RPM could be set via keypad, rather than rheostat. Similarly, rather than use limit switches, why not use a carriage position encoder and make the limits settable by keypad, for feeds in X&Y. Starting to sound a bit like CNC, but with manual controls and no programming capability?
 
The open source nature of this project suggests it can be developed and repaired for years to come. Is the Beel drive proprietary? If so then future support may be a challenge.

'Open Source' I like. Open BSD on all my pooters.

But this is a hardware issue. Analog at that.

BICL D510 is based off a design from the mid 1970's and built out of stock components whose makers publish reference circuits.

Eurotherm's design is newer and more sophisticated. Only about 20 years old by now.

You didn't think sub-ten-HP single-phase-input DC Drives were still bleeding-edge technology.

Or did you? If so.. the large-frame 3-HP Reliance just isn't all that picky.

Bill
 
.. with manual controls and no programming capability?

Cheap and easy, so long as that is OK.

Alternate 100 mm slide potentiometer. Light spring to make it's teat follow a length of rail that clamps to the cross. Bingo. radius-relevant RPM. Change the angle of the the rail to suit yer need.

Or use a stout copper wire and BEND it to the curve of choice.

Caveat: SSD use a single potentiometer for Forward (@ chosen RPM) <-OFF/BRAKE-> Reverse (@ chosen RPM)

Fastening a gallon can of paint to the faceplate and rocking the 10EE spindle back and forth to mix it is cheatin'.

Also damned slow compared to the mixers at paint stores.

:)

Bill
 
Since you have competition in the Beel drive ( thats already out there and has experienced that every 10EE can be different ) It seems foolish to spend 1500 in materials for something you can buy relatively economically.

I saw the Beel option in the following post - http://www.practicalmachinist.com/vb/monarch-lathes/10ee-solid-state-dc-motor-retro-fit-305500/ The Beel drive is an inexpensive chopped AC drive, far from a clean DC output and not really capable of full armature voltage with 230VAC input. Yes, the drive is reasonably functional option, but not what I'm looking for.

The drive I am working on can be more closely compared to the GE DC300 drives that someone sourced years back (minus the regenerative braking). Or, for $2000, here's a closer new comparison to what I'm working on - DC Drives | Non-Regen.(D), 3 Phase | D2Q1-1-1 - Driveswarehouse . At a glance, it looks like it could be a good fit, but note that it needs 3-phase input. Don't know much about it though. Might be able to get away with the 10HP version running on single phase. Or, the software might refuse to operate if missing a phase.

Anyway, the $1500 BOM cost is when built one-off. Could probably come down a few hundred dollars if built a few at a go. Yes, it's more expensive than what it could be if I had time to engineer the hell out of it. But, seeing as there's limited time and no profit to be had, the project is better suited for a design-by-overkill approach.
 
but note that it needs 3-phase input. Don't know much about it though. Might be able to get away with the 10HP version running on single phase. Or, the software might refuse to operate if missing a phase.

Hem's sake.... you've missed the basics entirely. There IS NO DC bank as a VFD has.

"Software" is analog. Potentiometers are the 'memory'.

DIGITAL controls on DC Drives generally start at 10 HP, 3-phase ONLY, and go UP. Where "UP" is 9,000 HP to 15,000 HP depending on maker. Those fill a small building. Or NOT so 'small'.

The ones in the range we use for a 10EE are ALL direct-off-the-line switchers. "Two-pulse" per cycle for a BICL D510, "six-pulse" for an El Cheapo 1Q 3-P equivalent.

Take away two of the three phases, the pulses go away with it.

A patent that probably expired Donkey's Years ago adds 'virtual' pulses by faking a bit of phase-shifting with more sophisticated triggering and pass-elements. Dunno if the GE does that or not. Have the manual. Don't have 3-P. Don't care how GE built it if I cannot use it.

But that 'trick' provides near-as-dammit 24-pulse off 3-Phase, and 'virtual' 8-pulse off single-phase.

Compare a D510 and an SSD-514C. SSD has eight inductors, four down each side of the PCB. Ever wonder what those DO on a single-phase ONLY DC Drive? The diagram is online.

And then... DC motors are far better 'integrators' of CURRENT - and it is Ampere-turns as does the motation, not Volts - than you have yet twigged to.

Ergo for motors in the range a 10EE cares about, SCR-class is good enough. So long as it doesn't have spikes a rectified-power-class motor (as-in "RPM" I, II, III) could live long and prosper with, but the older 'rotating power' era large-frame does not handle as well.

Bill
 
The ones in the range we use for a 10EE are ALL direct-off-the-line switchers. "Two-pulse" per cycle for a BICL D510, "six-pulse" for an El Cheapo 1Q 3-P equivalent.

Huh, guess I always assumed that the DC drives capable of full armature voltage on the 10EE had a capacitor bank in them and switched high-frequency. Thanks for the info.
 
Huh, guess I always assumed that the DC drives capable of full armature voltage on the 10EE had a capacitor bank in them and switched high-frequency. Thanks for the info.

Off-the-shelf drives of that class top-out at around 1 HP or half that. K-B and the other 'usual suspects' sell 'em, Galco and the other 'usual suspects' stock them. I have one for a Bison 1/5th HP gearmotor drive for power-longitudinal-feed on a tiny mill.

Their motors are too small to effectively integrate the pulses. Noisy acoustically if nothing else. Larger motors can do - more copper, more iron, more 'inertia', mechanical as well as electromagnetic, same AC Hz component, ergo don't need such 'perfect' power.

But there yah go.. didn't even read the online catalogs and spec sheets, didja?

Lot of folk out there doing 'ass u me' class Engineering. I started my Engineering career with high explosives. They DO NOT "forgive" even the tiniest little bit of such f**k ups.

Last thing you hear is a loud ringing noise in your ears.

Last thing as goes through yer mind is the pink mist that usta be yer arse.

Good training, that. Makes a body right THOROUGH as to reading the manuals, doing research before, not after, and paying attention in class.

:)

BTW .if it is ANY consolation.. before wandering-off to make-use of off-the-shelf SSD drives?

I 'had a dream' for a smoother 10EE drive as well

Big-arse old-school analog LINEAR PSU. Variable B+ supply for a broadcast transmitter sort of thing.

Downside is it wudda drawn more current and turned it into heat than my whole facility could deal with.

And not regulated all that well, anyway. They WANT to oscillate, y'see... so one has to damp the p**s out of 'em.

:)

Bill
 
Wow, tough crowd. Maybe a bit more explanation as to the why... I actually have need of a PMAC motor drive in a completely different application. Nothing out there that's a perfect fit (at least not for $1500). So, decided to spin my own and share it open-source (this is far from my first motor control design). Then, it occurred to me that with a modular design approach and a couple minor extras in the power circuit, it could also work beautifully for the 10EE. Thus my question regarding ideal I/O for a 10EE drive. At a minimum, I will develop a basic logic board for my own immediate 10EE needs. Long term, maybe I'll get around to the pseudo CNC that rimcanyon alluded to. Figured I would see if anyone else was interested in contributing before I finalize the design. Regardless, the overall drive project will continue.
 
FWIW,

I have a replacement solid state drive in my 1976 5HP 10EE. It like all the single phase drives I am aware of uses a step up transformer on the AC stage to achieve 230VDC. Fincor the make of my drive and, Sabina both made replacement drives for 10EE's The Beel drive needs a xformer as well to get full armature voltage.

I really wonder IF a three phase DC drive would work on single phase at a reduced output. I have several inverters that will work on single phase at 50% output. I have an inverter welder that will work on single phase that is sold as a three phase welder. A 10HP DC drive may be the answer?

Steve
 
I really wonder IF a three phase DC drive would work on single phase at a reduced output.

Few would last long even if they didn't trip on fault or were lied-to with kinky f***ery.

Thermal stress in a (usually) packaged bridge when only one pass-element was being fired, the others left cold.
 
You can get well over 240 VDC with some capacitors and have smooth DC in the process. The 3 hp motor is an extremely smooth one and should be fed good DC for best results. Somewhere back there I posted an analysis of the armature and commutator design that makes it almost devoid of "cogging", moving in jerks at very low speeds. I had a single phase unit going with a magnetic amplifier that gave smooth running and would only supply rated current to a locked rotor. It takes good capacitors though, because the current in and out of them is high. I doubt anyone would pay for it. Three phase works a lot better and only requires 1/3 the capacity. I have a good three phase magamp also, but I was looking at the single phase only market.

Personally, I think the motor should be run at 300 VDC with the neutral halfway between, 150 / 0 / -150 to avoid straining the insulation and less field weakening, which would give a more stable system. 300 V is well below the peak of full wave rectified 240 VAC.

Bill
 
You can get well over 240 VDC with some capacitors and have smooth DC in the process.

Aye, but... for wot that motor needs, they'd take up as much space as a fridge and cost more than filling it with decent champagne.

:)

And then one has to regulate that array. And price-in the cost of finite-life replacement as the caps age.

Nooo. 'active' elements give the leverage needed for less space, waste, and money.

Magnetics can be 'active'. Some right useful technology that most others have forgotten about.

Bill
 
Aye, but... for wot that motor needs, they'd take up as much space as a fridge and cost more than filling it with decent champagne.

3 hp?

The 120-265 VAC PFC front end (the part that turns Ac into 380-400 volts dc) in an Eltek rectifier.. is about 1.25 inches by 3.5 inches.. by about 8 inches.

The new ones are rated 3kw, delivering 48 volts at 62 amps, and yes the front end really is 98.5% efficient for about 97% full load efficiency.

OP could buy one or two of those and build two half bridges to supply pwm to the the rotor and field coil for less than half of his 1500 estimate.. 3hp would be pushing it due to motor efficiency, may need more than 3kw.

older versions are on ebay for about 100$ for a 2kw unit.
Eltek Valere H2���A 1 48V 4�A Rectifier | eBay
Eltek Valere 1U 48V Mini DC Power Supply H125�A1 NE Rectifier Modules | eBay
Eltek Valere H25��A1 VB 2�� 24�VAC 48V 42 56V � 5�A DC Black Rectifier | eBay


The 400v dc output of those rectifiers will be split above and below ground when fed from the American 120/240 grid. With appropriate LC filters after the IGBT half bridge, the motor will see DC.. with very little ac ripple current at say, 12khz or so. maybe 20 to keep the noise down.
 

Ever hear the term 'sandbagged'? Reliance Electric and Engineering built a business on doing that.

4.6 HP, actually. Sustainable.

5 HP, probably. Torque is MUCH higher than the 'small frame' units. Do the math. Those are 1750 or so RPM base.

Look at the size of the four brushes and the mass and area of the commutator bars. Compare that with a latter-day 5 HP RPM III. Smaller even at the higher FLA of my 180 VDC one. Compare with those of the main drive motor of a 1CM Continuous mining machine. Mind - it runs at higher voltage. It also delivers 100 HP, 3 shifts a day, and for years.

Reliance/Monarch de-rated the nameplate of that 'large frame' type T motor, turned right around and over-volted it per those same nameplate figures. Part of why they last so long and can still deliver a punch @ 2400 RPM when having only a 690 RPM base. Under load.

Free-running @ nameplate V for each of Armature and Field is about 850-900 RPM with VERY modest brush-timing in favour of FWD, close-on 1000-1100 RPM unloaded with max-aggressive bias to FWD.

And then... nominal 12 A or so FLA aside... in the 'real world' you'll want your power source to to be able to sustain 24 A for 60 seconds, sustain 16 A indefinitely, manage reversing / braking spikes of ~ 800 V with more energy "under the curve" than just minor annoyance, 1200 + V of lesser-energy spiking.

Ever reverse one of these Mike Foxtrot "Dinosaur Current" Type T (Rex) critters at the gallop?

Impressive. Very.

Just ship me your favorite armchair-selected magic box, 3 at a go.

I'll send back the remains, one per each motor as destroyed it.

:)
 








 
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