Ebikes are they AC, DC or?

Robocop fought that in one of the movies.

efMX Trials Electric Freeride said:
have you guys seen the Kubota ??

90


https://newatlas.com/automotive/kubota-autonomous-electric-tractor/
 
Ohbse said:
I'm guessing this is from that facebook discussion on the AC vs DC poll?

DC in - PWM is used to produce AC out is the short answer.

+1 though I'd add that the controller outputs pulses of DC, but the way it directs the pulses to the 3 different phases based on the commutation sequence the motor is getting AC.
 
So I asked a controller manufacturer.

Here was my question:

Hello,

I was wondering what is coming out of a controller like my 8080h. Is it DC, AC or a pwm signal?

Thanks.

And the answer:

Hi,

It is supposed to work with BLDC Motor with three hall sensors.
PWM signal techology is used to control the logic of controller.
The output is based on RMS current on the motor phase.
The input is DC current.
So it is PWM control logic for output.

Thanks,
Fany

So DC in pwm out. No AC going on.
 
John in CR said:
Ohbse said:
I'm guessing this is from that facebook discussion on the AC vs DC poll?

DC in - PWM is used to produce AC out is the short answer.

+1 though I'd add that the controller outputs pulses of DC, but the way it directs the pulses to the 3 different phases based on the commutation sequence the motor is getting AC.

Scoped output on a phase lead passes through zero and certainly doesn't look like pulses due to motor inductance, but you're also not wrong :)
 
John1deere said:
So I asked a controller manufacturer.

Here was my question:

Hello,

I was wondering what is coming out of a controller like my 8080h. Is it DC, AC or a pwm signal?

Thanks.

And the answer:

Hi,

It is supposed to work with BLDC Motor with three hall sensors.
PWM signal techology is used to control the logic of controller.
The output is based on RMS current on the motor phase.
The input is DC current.
So it is PWM control logic for output.

Thanks,
Fany

So DC in pwm out. No AC going on.

PWM isn't an output - it's a technique to FORM the output. The measured output on phase leads is an AC waveform, as alluded to in the 'RMS current on motor phase'. RMS is the average of a waveform that crosses zero.

Also, Kelly sales people are hardly an authority on motor inverter design - they tend to spontaneously explode :lol:
 
PWM doesn't have anything to do with this discussion. The width of the ON of each pulse (Pulse Width Modulation is PWM) that's occurring at something like 10,000 times per second is what is used to control the current flow for torque and give the motor what it sees as the "apparent voltage" to determine speed.

It's the order in which the controller sends the DC pulses to the different phases along with which other phase is open for the returning pulse from the motor that makes it AC. If you turn a BLDC motor it produces 3 phase AC too, and during operation that's what called BEMF.
 
+1 John.

Here's a relevant video for precisely this discussion, measuring the output of a 3 phase brushless motor using a scope. To quote the author "Because the ESC provides a 3 phase output using a PWM signal which is then smoothed out into a sinusoidal wave because motors are a purely inductive load"

[youtube]yY3VHfxVnJA[/youtube]
 
John1deere said:
So I asked a controller manufacturer.
So DC in pwm out. No AC going on.
That's like saying that there's a significant current flowing from your batteries to your motor, but no electricity, because no one used the word "electricity" when they described it to you.
 
Punx0r said:
That trace was a lot more sinusoidal than I was expecting from a cheapo turnigy RC controller!

Aren't they sensorless, and whatever the motor sends as BEMF is what determines the shape of the controller output other than the small steps resulting from the PWM frequency?
 
AFAIK the motor BEMF is used as the trigger to commutate but I was still expecting a pretty coarse/trapezoidal waveform?
 
Punx0r said:
AFAIK the motor BEMF is used as the trigger to commutate but I was still expecting a pretty coarse/trapezoidal waveform?

Now that I think about it, maybe this one has sinus output. A coarse trap form was/is probably a big part of the noise with RC rigs, since the motor alone is somewhat noisy even before props or the blender sound of big gear reductions.
 

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John1deere said:
progress is nice but being a farmer and knowing some about batteries i just can't see it happening anytime soon. when we are in a rush working 24/24 we just can't wait hours for a tractor to be charged... unless the price is so appealing that you can get let's say 3 instead of 2 conventional tractor (not just the cost of tractor but also operation.) same for custom worker they will need a way to charge in the field.
Who needs batteries !....
..or an operator ?
https://www.farmweekly.com.au/story/6217775/john-deere-trials-electric-tractor/
TCyfi4.jpg
 
Hillhater said:
John1deere said:
progress is nice but being a farmer and knowing some about batteries i just can't see it happening anytime soon. when we are in a rush working 24/24 we just can't wait hours for a tractor to be charged... unless the price is so appealing that you can get let's say 3 instead of 2 conventional tractor (not just the cost of tractor but also operation.) same for custom worker they will need a way to charge in the field.
Who needs batteries !....
..or an operator ?
https://www.farmweekly.com.au/story/6217775/john-deere-trials-electric-tractor/
TCyfi4.jpg

never even taught about cables lol we already do it with manure spreading. could totally work.
 
John1deere said:
progress is nice but being a farmer and knowing some about batteries i just can't see it happening anytime soon. when we are in a rush working 24/24 we just can't wait hours for a tractor to be charged...

The company's chief commercial officer Tim Sherstyuk said research on quick charging was focusing on minutes, similar to filling up a vehicle with diesel fuel.

"Our technology is able to decrease the irreversible chemical reactions that happen during charging, so that the same batteries can be charged fast without compromising cycle life."

Deere's eAutoPowr transmission in cooperation with Joksin Germany was awarded the only Gold Medal by the AGRITECHNICA Innovation Commission jury in 2019. The two brushless electric motors are virtually wear-free and powertrain durability exceeds any other concepts previously offered in the industry. In addition, the maintenance costs are significantly lower. The drive axles allow a traction increase and thus a significant slip reduction ... https://www.tvh.com/en-us/node/43192/john-deere-transmission-eautopowr

Deere wouldn't be developing an electric option for their 8R, 8RT Series Tractors if it wasn't economically profitable. Current retail prices for the diesel 8R Series tractors are $166,000 to $267,000 and $230,000 to $262,000 for 8RT Series tractors. Shipments of diesel 8Rs to dealers are expected this summer. ... https://www.deere.com/en/our-company/news-and-announcements/news-releases/2019/agriculture/2019nov10-agritechnica2019/

Progresses Marches On ... there's always one Big JD Producer-Operator in the province-state-county that has to have the first one whenever an 8R eAutoPowr option becomes available ... maybe as soon as 2022 ?? (wishful thinking? ... just a matter of time).
 
eMark said:
John1deere said:
progress is nice but being a farmer and knowing some about batteries i just can't see it happening anytime soon. when we are in a rush working 24/24 we just can't wait hours for a tractor to be charged...

The company's chief commercial officer Tim Sherstyuk said research on quick charging was focusing on minutes, similar to filling up a vehicle with diesel fuel.

"Our technology is able to decrease the irreversible chemical reactions that happen during charging, so that the same batteries can be charged fast without compromising cycle life."

Deere's eAutoPowr transmission in cooperation with Joksin Germany was awarded the only Gold Medal by the AGRITECHNICA Innovation Commission jury in 2019. The two brushless electric motors are virtually wear-free and powertrain durability exceeds any other concepts previously offered in the industry. In addition, the maintenance costs are significantly lower. The drive axles allow a traction increase and thus a significant slip reduction ... https://www.tvh.com/en-us/node/43192/john-deere-transmission-eautopowr

Deere wouldn't be developing an electric option for their 8R, 8RT Series Tractors if it wasn't economically profitable. Current retail prices for the diesel 8R Series tractors are $166,000 to $267,000 and $230,000 to $262,000 for 8RT Series tractors. Shipments of diesel 8Rs to dealers are expected this summer. ... https://www.deere.com/en/our-company/news-and-announcements/news-releases/2019/agriculture/2019nov10-agritechnica2019/

Progresses Marches On ... there's always one Big JD Producer-Operator in the province-state-county that has to have the first one whenever an 8R eAutoPowr option becomes available ... maybe as soon as 2022 ?? (wishful thinking? ... just a matter of time).

fills up in minutes similar to diesel, sure but how often? if you have to go back home every 2h to charge and the field is a 15-30min round trip... there's just not enough info to see if it's worth it or not. i think for field work the cable would be a better solution and for transport like bales then battery would be better but over here a lot is done by custom worker. how do you charge that amount of power remotely?

if only batteries could catch up to how great electric motors and controllers are... lol
 
AussieRider said:
The controller sends pulsed DC to the phase 1 coils, Then switches to phase 2, then phase 3. The confusion rises because there are 3 sets of "phase" coils but it's not 3 phase AC.
That said there are both BL AC motors and BL DC motors. 3 phase BL DC is "pulsed" direct current not to be confused with alternating (BL AC) current ... https://www.motioncontrolonline.org/products/ac-brushless-motors.cfm
 
eMark said:
That said there are both BL AC motors and BL DC motors. 3 phase BL DC is "pulsed" direct current not to be confused with alternating (BL AC) current ... https://www.motioncontrolonline.org/products/ac-brushless-motors.cfm

Not really true and somewhat confuses the issue further. AC induction (as in your link), PMAC (Permanent magnet AC) motors, BLDC or PMSM are all driven by AC wave forms (in the context of EVs of course)

Waveforms are created by pulse width modulated DC - view the video above :) The precise nature of the AC output will of course vary according to motor specification, however there are motor controllers out there such as the Sevcon that can be configured to run both AC induction and PMAC motors.
 
The controller sends pulses of DC at the PWM cycle rate. It's how those pulses of DC are directed to the 3 phases that makes it so the motor is getting AC. The switching from one phase to the next occurs at the commutation frequency that is based on RPM. The controller tries to make it a sine wave shape by manipulating the ON time,"Width", of the pulses. The older style "trap" controllers apparently change the width of the pulses in a linear manner resulting in a trapezoidal shape of its output, vs a sine wave controller changes the width of the ON pulses in a non-linear fashion to better approximate a sine wave shape.
 
eMark said:
That said there are both BL AC motors and BL DC motors. 3 phase BL DC is "pulsed" direct current not to be confused with alternating (BL AC) current ...
Nope. BLDC motors are AC motors; the controller creates the AC. (Yes, I know, the letters "DC" are in the name, but that's because they are intended as a replacement for mechanically commutated DC motors.)

You could make an argument that you can run a SR motor with unipolar switched DC and therefore it's a "true" DC motor, but you still need a controller, and the difference is largely academic.
 
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