DIY Turbopump Controller

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Nicolas Krause
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DIY Turbopump Controller

Post by Nicolas Krause » Thu Jan 14, 2021 6:39 pm

While I've purchased a TPM 50 turbopump for 100$ off of eBay, the device did not come with a controller. I'm unable to afford the purchase price of a new turbotronik controller, and while I've been looking on eBay, I haven't seen one come up for a price I can afford. I have a portion of the circuit completed in KiCad and I'm at the point where I have to start designing to power supply for the whole shebang. I'll need three different power levels, a 3.3V for the microcontroller and LCD screen, 15V for the driver chip (a FAN7388) and then 200V for the IGBT's that make up the driver circuit for the motor itself. I've been looking at the specs of the TurboTronik controller and it states that on startup it'll draw a maximum of 45W of power or 64VA. Given that it also specs that the voltage for each phase of the motor is 150V I've calculated the max current as 64VA/(1.73*150V)=246mA. So with a bit of a safety buffer a 200V supply that can also give up to 300mA of current should be alright no? This is the first time I'm designing an electronics project with this many moving parts and I just want to confirm I'm getting the basics right as I go forward.

John Futter
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Re: DIY Turbopump Controller

Post by John Futter » Thu Jan 14, 2021 6:59 pm

Nicolas
Look up my previous posts on this
I've built around 20 controllers for these. I used a simple 35-0-35 volt transformer to give me relay selected voltage of 45 volts and 90 volts to run the pump.
i switched supplies at approx half freq

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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause » Thu Jan 14, 2021 7:23 pm

Thanks for the reply John, I've found your design on the coulter smithing forums. Just to confirm a couple of things I'm reading about the device.
  1. There's no magnet sensor on the TPM 50
  2. Your design uses no microcontroller, but there is some digital logic, it looks like there's an output I assume to a computer down the line?
  3. If I run the pump at 90V will I get full RPMs? Or is the 150V the manufacturer specced just a standard engineering safety margin?

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Re: DIY Turbopump Controller

Post by John Futter » Sun Jan 17, 2021 2:03 am

Nicolas
The NT10 /NT13 controllers that were used we these devices used pwm and turned the pwm on / off so you heard a zip zip noise from the motor.
they used the on / off so they could use the higher voltage and still keep the motor windings cool.
My design did use a micro to generate the main freq to the 3phase logic generator and driver so micro did only monitor motor current and based on current it incremented the frequency when the motor current was below two amps. Net effect was the unit would accelerate to full noise in about 3 minutes in a leak free system.
Sorry did not include the micro stuff as it was proprietry to work ( some one elses work)

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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause » Sun Jan 17, 2021 3:11 am

I'd read that it was proprietary work on the original thread, no worries there, looks like a fun project for me to add a microcontroller. Besides, I've got a lot more faith in your circuit design skills than mine when it comes to the driver portion! I'm in the process of replicating your circuit at the moment in KiCad, I'll probably figure out all the components and circuit operation and then work on adding some firmware to control the whole thing.

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Re: DIY Turbopump Controller

Post by John Futter » Sun Jan 17, 2021 5:44 pm

i'll post some more when I get to work
I havent been there since 22/12/20 big holiday wiring up my new house

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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause » Fri Jan 22, 2021 7:03 pm

Hi John,

I've got a first draft of your schematic done up in KiCad, still have to build a bunch of footprints and possibly swap out a component or two, but lot of the basic work is done. I've also ordered a couple of the new Raspberry Pi Pico microcontrollers. They're very cheap, 4$, and seem to meet all the specs for what I need to do. So the next steps are to figure out the connections between the Pico and the pump controller circuit and then I can move on to layout once I've got a final version of the schematic.
Capture.PNG

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Re: DIY Turbopump Controller

Post by Peter Schmelcher » Sat Jan 23, 2021 9:19 pm

Nicolas these are internal pics of my NT10 controller circuit board before I repaired it but after cleaning with compressed air. It had previously been repaired by someone and was sold "as is". Unfortunately, I never found any schematics so I repaired it using these pics.

The NT10 controller spins up the turbo in discrete drive frequency steps with coasting between frequency increases. During the coasting moments the voltage produced by the motor windings are measured and used as a tachometer reading. As I recall the turbo needs to spin up within 2 minutes getting quickly through a 50Krpm mechanical rotor resonance.

Today my plan B repair would be a new variable frequency drive for a CNC router spindle ($130). The faster VFDs run up to 1000 Hz and I suspect that with a crystal change hack one could increase the upper frequency.
-Peter
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Nikodem Czechowski
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Re: DIY Turbopump Controller

Post by Nikodem Czechowski » Sat Jan 23, 2021 11:31 pm

Nicolas Krause wrote:
Fri Jan 22, 2021 7:03 pm
Hi John,

I've got a first draft of your schematic done up in KiCad, still have to build a bunch of footprints and possibly swap out a component or two, but lot of the basic work is done. I've also ordered a couple of the new Raspberry Pi Pico microcontrollers. They're very cheap, 4$, and seem to meet all the specs for what I need to do. So the next steps are to figure out the connections between the Pico and the pump controller circuit and then I can move on to layout once I've got a final version of the schematic.

Capture.PNG
Can you share the schematics in KiCad? Would love to join the work, I can (help) design the PCB, if you would like. Especially that I am looking for a controller for my Turbovac 50 :wink:

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Re: DIY Turbopump Controller

Post by Nicolas Krause » Sun Jan 24, 2021 1:16 am

Peter, thank you for photos and explanation of how the device measures the turbopump speed. I think at this point I'll press on with the custom design rather than the VFD option given the work John has already put into the circuit design.

Nikodem, I'm happy to share the schematic, I should warn you that it's missing some details and I swapped in some components I was missing in the library rather than build them out. It's a first draft, and I still have to put in connections for the microcontroller, LCD screen, on/off switch etc... As far as helping with the PCB design, I appreciate the offer but I like the work and I need the practice!

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