I don’t think that is how they work. Brushless dc is not inverted 3ph ac
Other treadmill/DC motor uses?
- Thread starter skeer
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Innovate1
Well-known member
Not sure where you get your information. My day job is working on them. There are a few other variations but almost all are inverters and 3 phase motors. Lot's of info if you want to check google. Here's a couple...
https://blog.orientalmotor.com/the-differences-between-brushed-and-brushless-dc-motors?
That page talks about sensors for shaft position but HVAC motors typically don't have actual position sensors and sense it indirectly from voltage and current -it's not quite the same as an inverter for an induction motor. The basic winding and driver details are the same.
https://www.renesas.com/us/en/support/engineer-school/brushless-dc-motor-02-inverter-pmw
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RaisedByWolves
Well-known member
Yes and no depending on the size of the press.
It would be OK drilling holes up to say 5/16-3/8" but a direct drive via the stepped pullies would lack power down low where you need it most. On a small say 10-12" press, yeah, you're not going above 3/8" anyway. On a 15" Drill press it will be very under powered.
I have done several and my primary DP has a 1/2HP Dayton motor that is very good. I have one up for sale noe with a 1/2HP Pacific scientific motor that is OK for general shop work, but the Dayton motor is twice the length and has much more torque than the PS motor.
I have several Treadmill motors (The PS is one of these but much more stout than the typical) and their basically 1/4th the size of the Dayton and 1/2 the size of the PS.
Vijeahos.
My atlas.
Innovate1
Well-known member
Treadmill motors run at higher speed than typical DP motors so for the same power you get less torque. To get similar torque you would need some additional speed reduction - either another stage or change the ratio of the existing.
Zeus36
Well-known member
You could hook a treadmill motor to a fan and have true variable speed. Window fan, Shop fan, Whole house fan...
Garcky
Well-known member
Never thought about that. Around here, treadmills are free on the curb, most weekends. Of course, you'd have to dispose of the rest of the thing, I guess. That might make it more difficult. I wonder if they're recyclable as shred iron?
I don't work on motors or have a day job that does it. lol....
you might have mistaken the similarity of the 120deg firing of the dc pulses (pwm or not) to each of the coils that looks like 3ph AC and the similarities of the wye winding between the motors.
maybe you can compare DC transmission lines and AC... both are 3PH per se.. but they are not the same.
Garcky
Well-known member
We got rid of one when we moved. Junk hauler. We paid to have it and other stuff hauled off. Hadn't been used for years. Exercise equipment is discarded all the time for that reason.
Nothing like that in my neck of the woods, either ppl are too poor to own treadmills or scavengers are rampant and efficient, things like that are gone before it even hit the curbs.
if you are scavenge the treadmill motors, make sure you get the controller with it. those higher power controllers are harder to come by.
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didn't want to side track the OP, as far as uses... I got two treadmill motors brushed ones and few 1/2 1/4 dc motors... original intend for the treadmill motors was to make a DIY windmill generator... if you have the land space and your town ordnance allows these things. Vertical or horizontal ones up to your imagination.
nadogail
Well-known member
I recently drilled an inch sized pulley to accommodate the metric shaft on the alternator I wanted to drive with a Vee Belt.
Innovate1
Well-known member
That note talks about 6 step commutation and later about sinusoidal output sensorless (actually they have sensors - the applied voltage must be kept in phase with the rotor on these type motors somehow. They indirectly sense position from voltage and current. Just one of the many confusing use of terms in the field). Figure 10 shows a "3 phase inverter bridge". 6 step was common maybe 30 or 40 years ago. Sinusoidal commutation is common today. I am not going to argue with you but I actually have a masters degree (MSEE) in power electronics and design drives for these type of motors. Have been for 30 years. And have almost that many patents. If you want to have a discussion that's fine. I think I know the basics. But I don't know everything and am always willing to be proven wrong or learn something new.
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That microchip link. the figure 10, block diagram of a 3phase inverter bridge is just a naming convention right ? figure 9 shows the internals and table 3 and 4 shows the sequence of how it was activating in pairs to redirect the points UVW to be both power and ground via the 6 transistors/MOSFET/LGBTs (Qs). The pulses are still DC and not AC. even if it is PWMed. There was a guy in youtube that converts the AC alternators to brush-less motors that have better explanation than me. Maybe if I look up that one, would be better.
Innovate1
Well-known member
I suppose you could call any name assigned to anything a naming convention. But the term 3 phase inverter is what it truly is and what people in the industry call it. Look up the definition.
Inverter: an apparatus which converts direct current into alternating current.
And the current does alternate or change direction.
A solid state circuit to generate 3 phase AC power would be the same (although the control of frequency would be different because the BLDC circuit has to be kept in phase/synchronous with the rotor). Most of that note deals with what are often called "six step" drives because there are 6 states of commutation (switching what coils receive power similar to a brush commutator in a brush motor) as seen in 3 and 4. Note that only two windings are used at a time. For the case of figure 10 it would apply power to all 3 phases at the same time and the applied voltage (averaged because it is applied as PWM, pulse width modulated) and current will be sinusoidal just like from a power utility (except for the higher frequency PWM which is sometimes filtered out between the control and the motor, usually only on fairly high power systems).
The pulses are positive and negative so looking at any one or group of pulses you could say it is pulsed DC. But it also has pulses of the opposite polarity so most people don't consider it DC because the polarity alternates, thus it is alternating voltage and current. Doing a quick search I see some on line say it is still a DC motor although the one I saw was referring to a 6 step method of drive. Most in the industry wouldn't say that.
Often for 6 step drive the motor is designed to have trapezoidal (flat topped) back emf. This is to better match the driving voltage and reduce torque variation as the shaft rotates. A lot of more modern motors have sinusoidal back emf and are driven with sinusoidal driving voltage and power all three windings all the time.
The terms used can get confusing. For example an induction or stepper or SR motor could be called brushless because they don't have brushes but the term is not usually applied that way because it is understood that those type motors never use brushes.
Innovate1
Well-known member
If it is a control for a treadmill motor that's a DC brush motor and the control is not an inverter - it never changes polarity. They are usually called chopper drives because they PWM or chop the DC to provide less than full voltage.My SIL bought this old mini lathe at a yard sale, rebuilt it and gave it to me for Christmas, Has a treadmill DC motor which gave the old lathe variable speed. He also had to make the inverter.
