I use a stepper motor (ex-printer) using a microstepping driver controlled by Arduino which is essentially a 2 phase AC signal. This means you can ramp the speed on start-up and stop. Takes only about 1 turn of platter to reach speed (or rest) but much better than instant full speed.
If you can control the frequency with 3 phase controller then smooth acceleration from rest should be possible.
Speed adjustment is by programming the frequency.
If you can control the frequency with 3 phase controller then smooth acceleration from rest should be possible.
Speed adjustment is by programming the frequency.
Why is it difficult to start the motor? When using 3 phase sinewave drive, it is very easy and you don't have to worry about starting in the wrong direction as long as you have the phases connected correctly.
That statement did confuse me so glad it was corrected.
Pyramid, the motor connection in your picture has only 3 pins. I would have thought a bldc run with your generator would require 4 pins. Could you explain please.
Thanks,
Kffern
It doesn't matter if the motor is delta wound (as the last one with the 1/4" shaft was) or wye wound (as the first one was), there are only 3 connections. There is no "common" or return lead, even when wye wound (the other side of the 3 windings are connected together to form a "Y", but there is no connection needed for this center node.
The ground connections on the signal generator are needed to complete the circuit with the amplifier inputs. The amplifier output grounds would be connected together, but the "hot" lead would go to each of the windings.
The ground connections on the signal generator are needed to complete the circuit with the amplifier inputs. The amplifier output grounds would be connected together, but the "hot" lead would go to each of the windings.
Can you run a 2 phase generator on a single phase hysteresis synchronous 3 wire motor. The Hurst motors are split phase so you lose the cap and run 90 degrees. This hysteresis motor also uses a run cap but no one seems to explain why it is there. There are so many variables in the motor game. So if the cap is use to shift 90 degrees like the Hurst maybe it would run smoother with out cap. If possible would need to know how to wire it because it is 3 wire instead of 4.
Thanks Tom
Thanks Tom
Tom-
I'm confused. Are you using the Hurst Hysteresis motor (DA/DB series)?
A single phase hysteresis motor would only have 2 wires. If it is split phase, the capacitor is used to feed the other phase as a HM doesn't require a starting cap.
If it is a split phase HM with 3 wires, it is nearly identical in hook up to the Hurst AC synch motors: 1 lead direct, 1 lead thru a phase cap and the 2 return leads (combined in your case internally so only one external wire) connected together.
Since I'm not sure what you are looking at, you will need to confirm the wiring diagram with the motor's data sheet.
I'm confused. Are you using the Hurst Hysteresis motor (DA/DB series)?
A single phase hysteresis motor would only have 2 wires. If it is split phase, the capacitor is used to feed the other phase as a HM doesn't require a starting cap.
If it is a split phase HM with 3 wires, it is nearly identical in hook up to the Hurst AC synch motors: 1 lead direct, 1 lead thru a phase cap and the 2 return leads (combined in your case internally so only one external wire) connected together.
Since I'm not sure what you are looking at, you will need to confirm the wiring diagram with the motor's data sheet.
Hi Pyramid
I decided to try a over the top really large motor. Found a deal on a hysteresis synchronous military surplus motor. It is 3 3/8 diameter 5 1/4 inches long. It is smooth even with a cap and straight out of the wall ac.
I put the diagram below. I measured the wires and it goes with the schematic. Orange to blue 19.2 ohms/ orange to black 104.5 ohms and black to blue 123.7 ohms. They use a 4 uf cap but l am not sure why it is there unless they are creating a 90 degree phase shift like Hurst does???
Well if I have to run this on 1 phase controller I am going to try it anyway. Will have to get larger power supply/ amp and transformer. If you know how to calculate what the amp sees load wise from the motor it would help me choose a bigger class d amp.
Thanks Tom
I decided to try a over the top really large motor. Found a deal on a hysteresis synchronous military surplus motor. It is 3 3/8 diameter 5 1/4 inches long. It is smooth even with a cap and straight out of the wall ac.
I put the diagram below. I measured the wires and it goes with the schematic. Orange to blue 19.2 ohms/ orange to black 104.5 ohms and black to blue 123.7 ohms. They use a 4 uf cap but l am not sure why it is there unless they are creating a 90 degree phase shift like Hurst does???
Well if I have to run this on 1 phase controller I am going to try it anyway. Will have to get larger power supply/ amp and transformer. If you know how to calculate what the amp sees load wise from the motor it would help me choose a bigger class d amp.
Thanks Tom
I've looked at some of the TI solutions, as well as Analog Devices and a rather interesting chip from PMD (MC73110 dedicated DSP motor controller). The main thing I didn't alike about any of these (besides cost and complexity) was they all required an optical encoder for speed feedback. I think the focus of most of these designs was lower vibration over speed accuracy. While both are important, IMHO accurate speed control and adjustment is the most important factor and vibration reduction is still achievable even while focusing on the former.
I've been doing some reading. the TI method doesn't use hall effect sensors or the typical feedback methods. But that may just be marketing that i dont understand. They sell an evaluation board but its something like $300.
In your tests, when you drive a BLDC with 3 phase sinusoidal signals, is it mimicing the usual trapezoidal signals where only 2 are energized at a time?
No it is completely different.
When using trapezoidal commutation, only 2 coils are energized as they use the 3rd winding as a sense coil to measure rotor position. This does not work well at low speed as the signal in the winding is very low and gets buried in the noise floor. FOC attempts to correct for this by de-rotating the signal induced in the stators by looking at the field from the rotors point of view in which the torque vector and the driving flux appear stationary (with respect to each other). Both methods use drive current to control the speed and let the rotor position determine when to commutate the drive signal. The motor can still exhibit cogging in this mode of operation.
By using 3 phase sinusoidal drive, the drive frequency determines the rotor speed, but the drive current has to be adjusted to maintain constant torque vs speed.
The 2 approaches are almost opposite: FOC controls the torque and the speed has to be compensated accordingly. 3 phase sinewave drive controls the speed and compensates the torque accordingly. It also works extremely well at low speeds and there is no problem with starting in the wrong direction.
When using trapezoidal commutation, only 2 coils are energized as they use the 3rd winding as a sense coil to measure rotor position. This does not work well at low speed as the signal in the winding is very low and gets buried in the noise floor. FOC attempts to correct for this by de-rotating the signal induced in the stators by looking at the field from the rotors point of view in which the torque vector and the driving flux appear stationary (with respect to each other). Both methods use drive current to control the speed and let the rotor position determine when to commutate the drive signal. The motor can still exhibit cogging in this mode of operation.
By using 3 phase sinusoidal drive, the drive frequency determines the rotor speed, but the drive current has to be adjusted to maintain constant torque vs speed.
The 2 approaches are almost opposite: FOC controls the torque and the speed has to be compensated accordingly. 3 phase sinewave drive controls the speed and compensates the torque accordingly. It also works extremely well at low speeds and there is no problem with starting in the wrong direction.
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Possibly. Which motor (what frequency) do you need it to put out? You will need to adjust the amplitude for your application.
It's not new tech and back in the 70s and 80s there were some very advanced drive setups from Japan for the big DD turntables. But for belt drives cheapy AC motors were, well cheaper so some of this was forgotten.
Nowdays there are solutions galore out there, but a lot of TT manufacturers, having spread FUD over DD in its heyday (Linn I am thinking of you here) don't want to admit that there is better.
Hi Bill
Did some more review and research on the motors you used and other options at Anaheim automation. I would like to try a larger output motor so it looked like the bly 172s 24v-2000 might do the trick. It is a 8 pole delta wound so would it be 40 hz for 600 rpm like the blwr 172s 24v-2000 you used?
Which brings us back to the sg4 (which I love!!!). Is the sg4 ok at 40 hz? I can adjust voltage at the voltage divider or amps (they have volume controls). I will only use it at 33.333. As always thanks for all the help.
Tom
Did some more review and research on the motors you used and other options at Anaheim automation. I would like to try a larger output motor so it looked like the bly 172s 24v-2000 might do the trick. It is a 8 pole delta wound so would it be 40 hz for 600 rpm like the blwr 172s 24v-2000 you used?
Which brings us back to the sg4 (which I love!!!). Is the sg4 ok at 40 hz? I can adjust voltage at the voltage divider or amps (they have volume controls). I will only use it at 33.333. As always thanks for all the help.
Tom