As long as the motor doesn't stall, the speed of the motor is determined by the frequency, not the voltage. The platter speed is affected by torque demands as the speed difference is manifested by increase/decrease in belt creep. If the torque demand of the platter remains constant, belt creep will cause it to rotate slower, but it should be constantly slower. If the belt isn't moving or is not twisted, it would indicate to me that something is sticking. I've also seen this when the bearing oil is too thick. I had a VPI platter that "rocked" back and forth with a sloppy bearing fit. I increased the viscosity of the bearing oil until the rocking ceased (finally stopping at SAE90), and the rev to rev stability was terrible. I went back to 3-in-1 oil and the speed was much more stable, so I lived with the rocking (eventually replaced both the platter and bearing).
There is not a huge difference between 40Hz and 36Hz wrt voltage; the lower the frequency, the lower the voltage, so if anything, you may be slightly high.
The drive system is somewhat sensitive to belt tension. Too low and the belt can slip, too high and belt creep will increase.
The RR tach averages the speed display over several revs, which could hide what is really happening rev to rev. Install solder jumper J1 on the PCB to disable averaging; it may give a clearer picture of what is happening.
There is not a huge difference between 40Hz and 36Hz wrt voltage; the lower the frequency, the lower the voltage, so if anything, you may be slightly high.
The drive system is somewhat sensitive to belt tension. Too low and the belt can slip, too high and belt creep will increase.
The RR tach averages the speed display over several revs, which could hide what is really happening rev to rev. Install solder jumper J1 on the PCB to disable averaging; it may give a clearer picture of what is happening.
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Thanks, Bill. My guess is that I might have belt creep. Will try another belt.
Thanks, Bill. My guess is that I might have belt creep. Will try another belt.
George, could you please clarify the position of each bearing, as they have different sizes?
Do you have any pictures of the replacement procedure or even pictures of the disassembled motor?
Thanks!
I'm still facing some small vibrations and maybe could be the bearings.
The small bearing - 607 - is on the bottom of the motor and the bigger - 608 - is on the top, near the pulley.
The motor is easy to disassemble. No photos right now, but in order to remove the bearings a bearing extractor like this is necessary : 3 Inch 2 Jaw Gear Puller Mechanic Bearing Steering Wheel Remover Extractor Tool | eBay
If you have vibrations, I thing is not the bearings. If the bearings go south, you will hear some motor noise. Maybe some issues with the motor pod?
The motor is easy to disassemble. No photos right now, but in order to remove the bearings a bearing extractor like this is necessary : 3 Inch 2 Jaw Gear Puller Mechanic Bearing Steering Wheel Remover Extractor Tool | eBay
If you have vibrations, I thing is not the bearings. If the bearings go south, you will hear some motor noise. Maybe some issues with the motor pod?
The machine shop used a boring bar on a CNC lathe to create the ¼" center bore. There was no way to hold the tolerance of a ¼" bore for the entire length of the pulley as the boring bar will deflect to much, so they cut the bore as long as they could and relieved the remaining length with a larger, non-critical diameter.
Will this amp do the job?
Sure Electronics AA-AB35281 3x200W Class D Audio Amplifier Board - T-Amp
Kind regards/Stefan
Sure Electronics AA-AB35281 3x200W Class D Audio Amplifier Board - T-Amp
Kind regards/Stefan
I think this amp might be OK for driving 115 or 230 V motors, using a separate transformer for each phase, but looking at the hardware it appears that each output is bridged, rather than referenced to ground. If true this means that you could not connect any of the output connections together; so you would have to separate both ends of each motor winding.
Depends on what job you are trying to do. Which motor would you be using it with? What are the motor requirements (voltage, power, frequency)?
What am I doing wrong?
I have built my 4th SG4 and 2nd MA3, driving a BLWS motor.
Sometimes the motor starts in the incorrect direction (counterclockwise) and sometimes correctly. I have it connected according the instructions, name black motor lead to 0 phase; red to 120 phase and yellow to 240 phase.
I thought I'd check it on a scope to see if everything looked OK from a phase standpoint. It appeared that the 120 phase connection output was actually 240 degrees out of phase and the 240 output was 120 degrees out of phase. Thinking I had something wrong with the MA3, I checked the SG4 output directly, and got the same results.
The output from the 120 is in the first photo and the output from the 240 connection is in the second photo.
What am I doing wrong? I suspect that I might have some setting on my 'scope screwed up.
Also why would the motor start in different directions?
Thank you.
I have built my 4th SG4 and 2nd MA3, driving a BLWS motor.
Sometimes the motor starts in the incorrect direction (counterclockwise) and sometimes correctly. I have it connected according the instructions, name black motor lead to 0 phase; red to 120 phase and yellow to 240 phase.
I thought I'd check it on a scope to see if everything looked OK from a phase standpoint. It appeared that the 120 phase connection output was actually 240 degrees out of phase and the 240 output was 120 degrees out of phase. Thinking I had something wrong with the MA3, I checked the SG4 output directly, and got the same results.
The output from the 120 is in the first photo and the output from the 240 connection is in the second photo.
What am I doing wrong? I suspect that I might have some setting on my 'scope screwed up.
Also why would the motor start in different directions?
Thank you.
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Do you have the scope settings for the two channels set to 'Chop' or 'Alt'? if the latter then what you see may well be affected by the trigger settings. In your pictures it looks like the yellow trace is being used to trigger the display(same relative position on screen).
It might be worthwhile showing a picture of the scope settings, so we can understand a little better what's going on.
It might be worthwhile showing a picture of the scope settings, so we can understand a little better what's going on.
As Ralph said, you will always want to trigger from the 0° output and use that as the reference.
The motor will run backwards if any two of the three lines are swapped. There should be no way the firmware can swap any of the outputs; it is hard coded and I've not heard of this before if it is a bug.
Is the motor under a severe load at start up? As the torque load increases, the angle between the rotating field and rotor will increase (this is what produces torque in the motor), but usually, if the angle exceeds 90°, the motor will just stall.
The motor will run backwards if any two of the three lines are swapped. There should be no way the firmware can swap any of the outputs; it is hard coded and I've not heard of this before if it is a bug.
Is the motor under a severe load at start up? As the torque load increases, the angle between the rotating field and rotor will increase (this is what produces torque in the motor), but usually, if the angle exceeds 90°, the motor will just stall.
I was assuming that I have something screwed up on my scope. I thought I was triggering off channel 1 which is the 0 degree output. But this scope is new to me so I might go back to my older one.
The motor may be under a fairly severe load. It's a very heavy VPI platter (12-14 pounds) so startup inertia would be substantial. Is there a cure for this?
Remember it doesn't consistently run backwards - sometimes its correct and sometimes in reverse. This was what really threw me for a loop
The motor may be under a fairly severe load. It's a very heavy VPI platter (12-14 pounds) so startup inertia would be substantial. Is there a cure for this?
Remember it doesn't consistently run backwards - sometimes its correct and sometimes in reverse. This was what really threw me for a loop