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Lowest electrical noise type of motor for low speed applications

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Someone:

--- Quote from: beanflying on May 24, 2020, 07:55:06 am ---
--- Quote from: nfmax on May 24, 2020, 07:44:51 am ---If the diameter of the turntable is large enough, you can use a flexible belt drive, as your torque and acceleration requirements are low. A speed reduction of 100:1 should be feasible. This is how they did it in record player turntables back in the day, though the primary concern was mechanical noise rather than electrical. Both shaded pole induction motors and BLDC motors were used.

With a suitably large moment of inertia, would it possible to simply turn the motor off briefly while you make your measurements, and let the turntable 'coast'?

--- End quote ---

He wants a turndown rate from 1-200 RPM which is not feasible with a single reduction.

--- End quote ---
When you open up design concepts (and your mind) a little, its not hard at all to meet those speed requirements with direct drive.... coming from experience putting precision motion right on top of low noise electronic sensing.

beanflying:

--- Quote from: Someone on May 24, 2020, 09:52:38 am ---
--- Quote from: beanflying on May 24, 2020, 07:55:06 am ---
--- Quote from: nfmax on May 24, 2020, 07:44:51 am ---If the diameter of the turntable is large enough, you can use a flexible belt drive, as your torque and acceleration requirements are low. A speed reduction of 100:1 should be feasible. This is how they did it in record player turntables back in the day, though the primary concern was mechanical noise rather than electrical. Both shaded pole induction motors and BLDC motors were used.

With a suitably large moment of inertia, would it possible to simply turn the motor off briefly while you make your measurements, and let the turntable 'coast'?

--- End quote ---

He wants a turndown rate from 1-200 RPM which is not feasible with a single reduction.

--- End quote ---
When you open up design concepts (and your mind) a little, its not hard at all to meet those speed requirements with direct drive.... coming from experience putting precision motion right on top of low noise electronic sensing.

--- End quote ---

When you consider the 'low noise' part of it initially requested it limits the options. If you ignore it then a stepper/gearbox makes a lot of sense but they are a long way from low noise.

So rather than 'open your mind' then offer ZERO how about you make a suggestion?

Someone:

--- Quote from: beanflying on May 24, 2020, 10:28:50 am ---
--- Quote from: Someone on May 24, 2020, 09:52:38 am ---
--- Quote from: beanflying on May 24, 2020, 07:55:06 am ---
--- Quote from: nfmax on May 24, 2020, 07:44:51 am ---If the diameter of the turntable is large enough, you can use a flexible belt drive, as your torque and acceleration requirements are low. A speed reduction of 100:1 should be feasible. This is how they did it in record player turntables back in the day, though the primary concern was mechanical noise rather than electrical. Both shaded pole induction motors and BLDC motors were used.

With a suitably large moment of inertia, would it possible to simply turn the motor off briefly while you make your measurements, and let the turntable 'coast'?
--- End quote ---
He wants a turndown rate from 1-200 RPM which is not feasible with a single reduction.
--- End quote ---
When you open up design concepts (and your mind) a little, its not hard at all to meet those speed requirements with direct drive.... coming from experience putting precision motion right on top of low noise electronic sensing.
--- End quote ---
When you consider the 'low noise' part of it initially requested it limits the options. If you ignore it then a stepper/gearbox makes a lot of sense but they are a long way from low noise.

So rather than 'open your mind' then offer ZERO how about you make a suggestion?
--- End quote ---
Because there are too many variables/parameters to make any serious suggestions. What constitutes "noise"? A single pole rotor (permanent magnet) could be driven to the specifications required with electronics similar to an audio amplifier, almost zero EMI but likely huge magnetic fringing fields. An ultrasonic motor would do it with no audible noise. Both without any gearing as direct drive. If every concept of "noise" is sensitive then the suggestions already provided of hydraulics are valid.

"noise" is even less clear than "low", together they're just marketing speak.

T3sl4co1l:
Float the turntable on water (or other hydraulic bearing), embed a bar magnet in it, and drive two coils in quadrature to position it.  Drive can be via DAC into linear power amp, so the digital MCU control stuff can be at some distance (use isolation?) from the amplifier and compass\\\\motor.

You know, like they did it two centuries ago. ;D ;D

Tim

filssavi:
BLD
--- Quote from: T3sl4co1l on May 24, 2020, 12:37:34 pm ---Float the turntable on water (or other hydraulic bearing), embed a bar magnet in it, and drive two coils in quadrature to position it.  Drive can be via DAC into linear power amp, so the digital MCU control stuff can be at some distance (use isolation?) from the amplifier and compass\\\\motor.

You know, like they did it two centuries ago. ;D ;D

Tim

--- End quote ---

What you are suggesting is a poor man BLDC, then he might just as well use a proper one...

The problem with BLDCs is that, similarly to steppers they are usually driven By fully energising a phase at a time, that  has its advantages (mainly its cheap) But will generate quite a lot of noise. The least noisy way to drive a machine is with sinusoids (ok it is not that simple I know but let’s not go too much into details) so PMSM (also knows as BLAC) or induction machines

Also the placement for the MCU is completely irrelevant, as the machine drive and machine themselves will spew out much much more EMI

Last but not least I would strongly Advice against rolling your own drive, as if you don’t have experience in the field it is pretty much guaranteed you will fail even the most basic compliance test, let alone do better than what you find on the market

Also provided you are willing to spend I am sure you can find off the shelf solutions to the problem as your problem is common in many T&M specialities

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