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skyl4rk
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Safe, I may have missed the discussion in a previous thread, but did you rule out a brushless permanent magnet motor?
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The AC Induction Motor Ebike Project
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safe
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I have to back up a bit before I answer that...
My "concept" is for a racing class to be invented where the power input is limited to a very precisely metered 1000 watt value so that the approximate average output is 750 watts which satisfies the legal definition of an "ebike" in America. (based on the Federal Ebike Law) The basic idea is that if we are to have an "ebike racing category" then the rules are going to have to be strict enough so that there is no crossover into the emotorcycle category.
The stuff that Recumpence has been doing with RC brushless motors does a good job of proving the point that the RC brushless permanent magnet motor is a quick way to get something powerful... but it's also very illegal.
So instead of the quest for more and more peak power (which is pointless because there is no legal framework for such things) I'm trying to develop a racebike along the concept of an ebike racing class that is limited to 1000 watts of input.
Is this a foolish and pointless path to take?
Well... maybe... at least if I do build something and it delivers a really flat powerband like I want it to then there is the potential for a future in that I might decide to manufacture it as an actual product for sale.
The limitation of permanent magnet motors (brushed or brushless) is that the magnets set a very limited powerband upper limit (the no load speed) and this means that in order to actually have a racebike you would need to use multispeed gears.
With the AC Induction motor it's just a simple change in the frequency limit... no changes needed on the hardware side... so that the fully street legal EBRR ("Electric Bicycle Road Racer") bike goes from a 20 mph limit, a 30 mph limit or unlimited depending on the upper frequency permission setting. The changes would be done in the controller and no other changes would be required. (so it's a more flexible design from the legal standpoint) The AC Induction motor with 4 poles has a very low base rpm (1800 rpm) compared with the permanent magnet motor that will spin faster. (4000 rpm) This will allow the AC Induction motor to operate without the need for multispeed gearing... or primary geardowns (usually about 10:1)... which is a big plus because these bikes are already getting too complex.
I've attempted to express a comparison as best as I know of how the two motors might compare. Anything with a permanent magnet is going to have a flat torque curve with a very definite ending. (no load speed) The AC Induction motor continues to deliver power even though the frequency is allowed to rise. (at reduced levels, but it's still rising)
The Image:
http://www.motoredbikes.com/attachment.php?attachmentid=20846&d=1252251821
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safe
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Transformers Too Heavy
From what I've been able to find on the internet so far (not an all inclusive observation, so help me out if you know better) it's hard to find an inverter that doesn't weigh a lot. It seems that they are probably building the standard inverter with a transformer to serve at least some role. At nearly 10 lbs most of these inverters are simply too heavy to be used on an ebike.
So instead of the retail inverter I'm looking at the old school Cockroft Walton Voltage Multipliers that look like this:
...the idea is that you push and pull an AC current from the bottom and the diodes cause the voltage to step up. The nice thing about these circuits is that they tend to be rather efficient... in the 90%-95% range. Increasing the voltage going to the motor increases it's efficiency, but the more you step up the voltage the more losses you get, so it's going to be some happy compromise about how much to step up. You then get simple DC for output which is perfect for the second part which is to create a Three Phase waveform. (that's the part where you need a custom chip or a PIC in order to figure out the algorithms to act as the VFD)
One of the charactoristics of the Cockroft Walton Voltage Multiplier is that increased current produces voltage sag. If I were of the mindset of wanting to increase power output beyond a certain point this design would be frustrating because you would run up against a limit as far as power output peak. But here I'm actually "lucky" that my stated goal is to keep the power limited to a maximum of 1000 watts. With a 1000 watt input restriction you can design the voltage multiplier:
...so that it cannot exceed 1000 watts of power.
From the legal standpoint this would help because it says that people who want to try to modify the controller for more power will have a hard time doing it without removing many of the components.
So the design will serve as both a way to step up the voltage and also prevent a future user from increasing the power beyond 1000 watts.
I'm still going to want to use a current sensor on the battery to know whether I'm trying to use a frequency (high throttle position) that is too high. A frequency setting that is too high will cause the motor to draw excessive current to try to attain the synchronous speed which is both bad for reasons of heating and also violates the 1000 watt input rule. This built in structural limitation for power input will be another layer that will make illegal power modifications harder to do. (and protect the motor too)
The police will like the fact that I'm building in all these things that make illegal power harder to do and that increases the acceptance potential of the product. The bike might look illegal on the outside, but it will likely be legal on the inside.
-------------------------------
To be honest this is looking to be a very challenging project to pull off. It's no wonder no one has done this yet because it's not an easy thing to do. It just seems like there are few products available that fit the needs of an AC Induction motored ebike. (despite the fact that industry has been using Induction motors for years there is a limited supply of parts that apply well for the project)
From what I've been able to find on the internet so far (not an all inclusive observation, so help me out if you know better) it's hard to find an inverter that doesn't weigh a lot. It seems that they are probably building the standard inverter with a transformer to serve at least some role. At nearly 10 lbs most of these inverters are simply too heavy to be used on an ebike.
So instead of the retail inverter I'm looking at the old school Cockroft Walton Voltage Multipliers that look like this:
...the idea is that you push and pull an AC current from the bottom and the diodes cause the voltage to step up. The nice thing about these circuits is that they tend to be rather efficient... in the 90%-95% range. Increasing the voltage going to the motor increases it's efficiency, but the more you step up the voltage the more losses you get, so it's going to be some happy compromise about how much to step up. You then get simple DC for output which is perfect for the second part which is to create a Three Phase waveform. (that's the part where you need a custom chip or a PIC in order to figure out the algorithms to act as the VFD)
One of the charactoristics of the Cockroft Walton Voltage Multiplier is that increased current produces voltage sag. If I were of the mindset of wanting to increase power output beyond a certain point this design would be frustrating because you would run up against a limit as far as power output peak. But here I'm actually "lucky" that my stated goal is to keep the power limited to a maximum of 1000 watts. With a 1000 watt input restriction you can design the voltage multiplier:
...so that it cannot exceed 1000 watts of power.
From the legal standpoint this would help because it says that people who want to try to modify the controller for more power will have a hard time doing it without removing many of the components.
So the design will serve as both a way to step up the voltage and also prevent a future user from increasing the power beyond 1000 watts.
I'm still going to want to use a current sensor on the battery to know whether I'm trying to use a frequency (high throttle position) that is too high. A frequency setting that is too high will cause the motor to draw excessive current to try to attain the synchronous speed which is both bad for reasons of heating and also violates the 1000 watt input rule. This built in structural limitation for power input will be another layer that will make illegal power modifications harder to do. (and protect the motor too)
The police will like the fact that I'm building in all these things that make illegal power harder to do and that increases the acceptance potential of the product. The bike might look illegal on the outside, but it will likely be legal on the inside.
-------------------------------
To be honest this is looking to be a very challenging project to pull off. It's no wonder no one has done this yet because it's not an easy thing to do. It just seems like there are few products available that fit the needs of an AC Induction motored ebike. (despite the fact that industry has been using Induction motors for years there is a limited supply of parts that apply well for the project)
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safe
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Cockroft-Walton Voltage Multiplier Calculator
http://www.cosmicrays.org/muon-cockroft-walton-calculation.php
It sure would have been great if I had found something like this for motor rewinding. The link is to an online calculator so that you can figure out what combination of capacitors and frequency will produce an efficient system.
Basically the "good" things to have are:
Higher Capacitance
Higher Switching Frequency
...many of the chips I've seen for High / Low Drivers operate at speeds of 300 kHz or more. That compares to about 20 kHz for a normal PWM controller.
So speed is good... faster clock speeds translate into being able to use smaller and less expensive capacitors to achieve the increased voltage.
Full Wave circuits require more capacitors than Half Wave, but the capacitance can be about half to achieve the same end, so it balances out.
http://www.cosmicrays.org/muon-cockroft-walton-calculation.php
It sure would have been great if I had found something like this for motor rewinding. The link is to an online calculator so that you can figure out what combination of capacitors and frequency will produce an efficient system.
Basically the "good" things to have are:
Higher Capacitance
Higher Switching Frequency
...many of the chips I've seen for High / Low Drivers operate at speeds of 300 kHz or more. That compares to about 20 kHz for a normal PWM controller.
So speed is good... faster clock speeds translate into being able to use smaller and less expensive capacitors to achieve the increased voltage.
Full Wave circuits require more capacitors than Half Wave, but the capacitance can be about half to achieve the same end, so it balances out.
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Three one hundred and twenty degree Phased Cockroft Walton Particle accelerators delivering , Their energy into a WYE shaped copper (soon to be plasma) vortex.
EVER HEAR OF A TRAVELING GROUND FAULT?
Wayy to much Back to the Future.
ONE POINT TWENTY ONE JIGGAWATTS OR SO RIGHT!
How about a three phase 110 volt dc washer motor with a custom controller
Look here
http://cgi.ebay.com/FISHER-PAYKEL-T...emZ300344651607QQcategoryZ71256QQcmdZViewItem
A FISHER-PAYKEL-Top-Load-Washer-Washing-Machine has a three phase 110 volt dc motor with a built in adjustable motor controller .
No transmission, no belts, Direct drive from 0 up to 1000 rpm.
Part of me actually wants to see your version of a Flux Capacitor at night . Every thing faintly glowing.
EVER HEAR OF A TRAVELING GROUND FAULT?
Wayy to much Back to the Future.
ONE POINT TWENTY ONE JIGGAWATTS OR SO RIGHT!
How about a three phase 110 volt dc washer motor with a custom controller
Look here
http://cgi.ebay.com/FISHER-PAYKEL-T...emZ300344651607QQcategoryZ71256QQcmdZViewItem
A FISHER-PAYKEL-Top-Load-Washer-Washing-Machine has a three phase 110 volt dc motor with a built in adjustable motor controller .
No transmission, no belts, Direct drive from 0 up to 1000 rpm.
Part of me actually wants to see your version of a Flux Capacitor at night . Every thing faintly glowing.
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safe
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When you connect the wires to make up a 48 volt DC connection you get a large spark. Increase that to 72 volts DC and it gets worse. By 110 volts DC you can easily kill someone. (people have died at 50 volts DC) DC power tends to make the victim freeze up when they touch the wire.
AC power, on the other hand, tends to make the victim release the wire and so higher voltage AC is less dangerous. I know that I've been electrocuted by a standard 120 volt AC line and while it's not fun it isn't that bad if you pull your hand away.
I'm thinking of a 48 volt DC base battery voltage which I then step up two or three times to either 100 volts AC or 150 volts AC Three Phase power. The idea would be to make the higher voltage components better shielded so that it's unlikely that a short occurs. Each phase will carry only a part of the overall power, so you reduce the risk once the power gets divided.
The bigger danger is the DC than the AC in my opinion... (it's the connection that is dangerous) It's possible to use higher voltage DC and then include a contactor... that's definitely a possibility... however, that still means that there is an exposed line of high DC voltage in the system.
If a danger exists I'd rather it be AC than DC...
Also, these voltage multipliers tend to be pretty safe in that each stage only sees the voltage step it is doing, so the parts aren't stressed with the full voltage. A ground fault would be bad, but since this is something that can be contained in an insulated container that should be manageable.
The peak danger is between the step up and the Three Phase power. The "in between" DC voltage will be high... but again... that can be shielded behind an insulated container.
http://en.wikipedia.org/wiki/High_voltage
Voltages of greater than 50 V applied across dry unbroken human skin are capable of producing heart fibrillation if they produce electric currents in body tissues which happen to pass through the chest area. The electrocution danger is mostly determined by the low conductivity of dry human skin. If skin is wet, or if there are wounds, or if the voltage is applied to electrodes which penetrate the skin, then even voltage sources below 40 V can be lethal if contacted.
http://en.wikipedia.org/wiki/Electric_shock
It is sometimes suggested that human lethality is most common with alternating current at 100-250 volts; however, death has occurred below this range, with supplies as low as 32 volts. Danger increases dramatically with voltages over 250 volts. Shocks above 3300 volts are usually fatal, and those above 11000 being mostly fatal.
My online name is "safe" so I'm trying to live up to my name.
AC power, on the other hand, tends to make the victim release the wire and so higher voltage AC is less dangerous. I know that I've been electrocuted by a standard 120 volt AC line and while it's not fun it isn't that bad if you pull your hand away.
I'm thinking of a 48 volt DC base battery voltage which I then step up two or three times to either 100 volts AC or 150 volts AC Three Phase power. The idea would be to make the higher voltage components better shielded so that it's unlikely that a short occurs. Each phase will carry only a part of the overall power, so you reduce the risk once the power gets divided.
The bigger danger is the DC than the AC in my opinion... (it's the connection that is dangerous) It's possible to use higher voltage DC and then include a contactor... that's definitely a possibility... however, that still means that there is an exposed line of high DC voltage in the system.
If a danger exists I'd rather it be AC than DC...
Also, these voltage multipliers tend to be pretty safe in that each stage only sees the voltage step it is doing, so the parts aren't stressed with the full voltage. A ground fault would be bad, but since this is something that can be contained in an insulated container that should be manageable.
The peak danger is between the step up and the Three Phase power. The "in between" DC voltage will be high... but again... that can be shielded behind an insulated container.
http://en.wikipedia.org/wiki/High_voltage
Voltages of greater than 50 V applied across dry unbroken human skin are capable of producing heart fibrillation if they produce electric currents in body tissues which happen to pass through the chest area. The electrocution danger is mostly determined by the low conductivity of dry human skin. If skin is wet, or if there are wounds, or if the voltage is applied to electrodes which penetrate the skin, then even voltage sources below 40 V can be lethal if contacted.
http://en.wikipedia.org/wiki/Electric_shock
It is sometimes suggested that human lethality is most common with alternating current at 100-250 volts; however, death has occurred below this range, with supplies as low as 32 volts. Danger increases dramatically with voltages over 250 volts. Shocks above 3300 volts are usually fatal, and those above 11000 being mostly fatal.
My online name is "safe" so I'm trying to live up to my name.
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Fifteen joules of any type of electric delivery system .
Ac , dc microwave, electrostatic you name it is lethal.
Ac holds you just as hard as dc.
The same muscles are contracting..
The only rule is keep your left hand away from it.
I can see it now .
A tiny flaw in the insulation, a bubble of gas.
Under the intense electric stress, grows warm.
Finally the gas starts to conduct well.
A tiny spark appears outside the insulation,
warming the surrounding air.
Quickly quenched by the magnetic field's.action on it.
Alternately stared and quenched at thousands of times a second.
Finally it achieves a phenomenon called Avalanche.
This will let the magic smoke out quickly.. .
If you are very lucky the fuse will blow.
If not well, up one leg and down the other LOL.
Ac , dc microwave, electrostatic you name it is lethal.
Ac holds you just as hard as dc.
The same muscles are contracting..
The only rule is keep your left hand away from it.
I can see it now .
A tiny flaw in the insulation, a bubble of gas.
Under the intense electric stress, grows warm.
Finally the gas starts to conduct well.
A tiny spark appears outside the insulation,
warming the surrounding air.
Quickly quenched by the magnetic field's.action on it.
Alternately stared and quenched at thousands of times a second.
Finally it achieves a phenomenon called Avalanche.
This will let the magic smoke out quickly.. .
If you are very lucky the fuse will blow.
If not well, up one leg and down the other LOL.
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safe
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No matter how you slice it I will be using 1000 watts of input power. You can increase the voltage and reduce the current, but the total power is going to be the same.
The fact of the matter is that ALL the ebikes are already pushing enough power to do some damage... there are folks that are using 6000 watts of power and that means that if they got a short it would seriously hurt.
What I'm doing is "normal" in that it's within the same level of power that is already being used. From a "safety" perspective there is no such thing as perfection, so all that can be done is to use proper techniques to insulate the components.
Probably the better way to look at is that the dangers are already there... and it's only when you are looking more closely that you realize the way things already are.
I'd rather get an AC shock than DC given the choice.
The voltage I will be dealing with is the same as household electricity, so it's not rocket science.
The fact of the matter is that ALL the ebikes are already pushing enough power to do some damage... there are folks that are using 6000 watts of power and that means that if they got a short it would seriously hurt.
What I'm doing is "normal" in that it's within the same level of power that is already being used. From a "safety" perspective there is no such thing as perfection, so all that can be done is to use proper techniques to insulate the components.
Probably the better way to look at is that the dangers are already there... and it's only when you are looking more closely that you realize the way things already are.
I'd rather get an AC shock than DC given the choice.
The voltage I will be dealing with is the same as household electricity, so it's not rocket science.
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The NEC Doesn't care if a system does not even work, as long as it does not hurt someone. When its not working, It does not even have to be sized for the job.
You do need to prove competence to work on household wiring.
A licensed Journeyman Electrician.
Authorized by ,The authority having jurisdiction.
Usually a state board..
works for.
A licensed Contractor who may hire Journeymen to work for him , as well as sue and be sued.
The specialty licenses go into low voltage under 50 volts, or
Over six hundred volts.
Most dont need them.
Only then can they do work on a home or business.
If you meet the requirements for the UL.certification.
The Underwriters Laboratory U L for short will need to pass judgment on your setup. If it doesn't pass, and you sell it to the public expect to be sued a lot.
You do need to prove competence to work on household wiring.
A licensed Journeyman Electrician.
Authorized by ,The authority having jurisdiction.
Usually a state board..
works for.
A licensed Contractor who may hire Journeymen to work for him , as well as sue and be sued.
The specialty licenses go into low voltage under 50 volts, or
Over six hundred volts.
Most dont need them.
Only then can they do work on a home or business.
If you meet the requirements for the UL.certification.
The Underwriters Laboratory U L for short will need to pass judgment on your setup. If it doesn't pass, and you sell it to the public expect to be sued a lot.
safe
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You're talking about getting a UL certification and I'm not even sure if the concept is viable yet. Right now it's "pioneering research" to see how it might work. Long before any factory started to produce anything I'd be sure to go through every element of legal red tape there is and get everything past inspection. (you have to pass all the safety laws for bicycles as well as the federal ebike law)
I would never manually build these bikes for sale... that would be insane.
The idea is to discover what works and what doesn't and what is legal and what isn't and eventually get to a point where a product might be made. But that's so far away right now that it's not worth worrying about.
I would never manually build these bikes for sale... that would be insane.
The idea is to discover what works and what doesn't and what is legal and what isn't and eventually get to a point where a product might be made. But that's so far away right now that it's not worth worrying about.
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