TD-124 motor speed

[Kal Rubinson]

Does anyone know the loaded and unloaded motor speed of the E50 motor?

Kal

[Kal Rubinson]

Found the answer: "The motor runs 1500 rpm (50Hz) or 1800 rpm (60Hz), but the turntable runs only between 16 and 78 rpm."

[Geneml]

Originally Posted by Kal Rubinson

Does anyone know the loaded and unloaded motor speed of the E50 motor?

Kal

kal, the motor speed also depends on the eddy current brake. Actually, not only does it slow down the motor, but it helps to smooth-out the 4-pole fluctuations of the shaded-pole motor.

[kevinkr]

Not quite that simple as I found to my surprise - this is a shaded pole induction motor, and while synchronous it does not run at the speed one would normally expect. According to "Swiss Precision" the motor runs at nominally 1350rpm on 50Hz, and on 60Hz this would be 1620rpm which if you do the math on a shaded pole induction motor indicates that this motor is synchronous as one would expect.

These motors exhibit a deliberate amount of controllable slippage which is not the case with a conventional synchronous motor, loading on the motor determines the amount of slippage, and there is a finite amount of slippage that can occur before the motor looses lock which is I think significantly beyond the range the eddy current brake.

Motor speed is a function of the setting of the eddy current brake as Genemi states. Hope you did not find the incorrect speed information in my TD-124 restoration thread. (I only found this information out when I got the Swiss Precision for Christmas.)

You can find the required math on any site dealing with the Siemens MicroMaster 410 ac motor drive and the like.

Incidentally a properly restored motor exhibits excellent speed stability as long as the TT main bearing is in good shape. Earlier plastic sleeved main bearings have a tendency to seize and as they fail the drag just continues to increase as the table runs until it doesn't..

Fully warmed up mine has not required a speed adjustment in a month or more of nearly constant use. Note that when cold it may run 1% or more slow.

[Mark Kelly]

Yes, it's a shaded pole (induction) motor which means it isn't synchronous by definition. If it were synchronous there would be no induction (which is caused by slip), also the eddy current brake would't work.

The figures from Audio Precision sound about right, shaded pole motors generally slip by around 10-15% depending on torque load.

[Geneml]

Originally Posted by Mark Kelly

Yes, it's a shaded pole (induction) motor which means it isn't synchronous by definition. If it were synchronous there would be no induction (which is caused by slip), also the eddy current brake would't work.

The figures from Audio Precision sound about right, shaded pole motors generally slip by around 10-15% depending on torque load.

What about voltage? How does that affect speed?

[kevinkr]

Originally Posted by Geneml

What about voltage? How does that affect speed?

Not by as much as you would expect, large changes (20% or more) seem to only affect speed by a few %, however it does affect torque significantly.

[kevinkr]

Originally Posted by Mark Kelly

Yes, it's a shaded pole (induction) motor which means it isn't synchronous by definition. If it were synchronous there would be no induction (which is caused by slip), also the eddy current brake would't work.

The figures from Audio Precision sound about right, shaded pole motors generally slip by around 10-15% depending on torque load.

I didn't explain that too well.. I should have avoided the term "synchronous" although in the E50 the mains frequency is the biggest determinant of what speed the motor will run at, with loading being next (slippage), and voltage being last. The last two are a relatively small percentage of the total. I don't completely trust the numbers quoted for these effects elsewhere - so won't quote them here.

[jackinnj]

If you could get an LP with an impulse, chirp or square wave, would be interesting to put vibration sensors on several locations and take a look at how the system responds to these types of stimulus.

[audiosilente]

the td 124 motor is not a syncronous motor, but a normal ac induction motor. the td 124 have 2 motors . mk1 version and mk2 versione. the mk2 version is more good than mk1. the coils have a different structure. size of coil is 0.4mm more than mk1 version. best speed with laser test 50 hz is 1450 rpm. all mk2 version have more dinamic than mk1. i have repaired over 1000 td 124 :-) sorry for my poor english simone