erics wrote:inverters tend to create electro-magnetic interference (EMI).

You imply the EMI is put on the electrical grid, but would it also be broadcast?

erics wrote:if your "significant other" happens to be watching the daily soaps on TV

As we do not have TV, I would be worried also about air-borne EMI/RFI that is received by my audio (0-MHz bandwidth).

erics wrote:Now, filter cards inherently leak a little current to ground

Thinking out of the box here. Thinking of my vacuum cleaner (Electrolux), 1600W electrical power with a GE turbine of 425W suction. If you were to switch on its 1600W motor, knowing an electric motor has 0 Ohm internal resistance initially, then you know an infinite current will flow when switching it on without any control device. So what did the nice vac sucker people do? Add in a circuit that slowly revs up the motor. Plus they put a UI on it for me the user to be able to reduce suction if/where necessary.
Back to EMI. This thing is very silent electrically as perceived by my stereo. (No I do not use AC filtering or re-genration or AC wave synthesis à la PSAudio.)
I just do not know if the motor is 1 or 3 phase. Probably 1 (no inverter then?). And the big dust sucker has no ground connection. Part or all of our required solution apparently is out there.
Now here I get back to my question:

CafSuperCharged wrote:What about other motors that are used in espresso machines - do they all require some control/drive unit? What is the rationale here?

I understood the espresso related rationale, however my reasoning is based on the physics knowledge of a 14 year old grammar school pupil of about 42 years ago.
What is the rationale of controlling electrical motors other than the one I described above?

Regards
Peter

I think it is a brushless DC type motor and a controller is required to run it. The motors are very efficient and can be sealed to keep out coffee grinds. They cost a lot more then typical AC motors other wise we would see alot more of them.

Hi guys,

I also think it's a DC motor* and I'm quite convinced it's controlled with PWM, that's why you need that black box to run it. Without it you would have to connect it to a DC power supply and you'd only get one speed (3500RPM).

Would be nice to get a DC motor to run an ordinary rotary pump, it could be easily controlled to get various speeds/pressures. Does FOT sell motors as well?

Regards,
dsc.

*EDIT: nope it's an AC motor, the controller is there simply acting as VFD.

CafSuperCharged wrote:You imply the EMI is put on the electrical grid, but would it also be broadcast?

One pretty much implies the other. Any waveform with sharp transitions (square waves or spikes) has a large high-frequency component, which tends to radiate from pretty much anything. Including power lines.

A traditional homebrew amateur radio builder's complaint was that it too often seemed easier to get the signal to the power lines than the antenna!

Hi guys,

anyone tried or thought of using this instead:

http://fluid-o-tech.com/files/Mg.pdf

??

the flow ratings are significantly lower.

Regards,
dsc.