Field weakening, is there another name?
- Thread starter anon4
- Start date
Also known as Flux weakening. AFAIK this feature is only found on top of the line hi tech controllers like Sabvoton, Phaserunner etc. Calling these overpriced is prob. a bit unfair as they have features and abilities we can only dream of with our £20 Chinese junk ones! When means allow, I will deff. invest in a Phaserunner and find out what it's all about.
Yeah they are definitely an achievement but I'd never pay it. I have read of one or two people buying a cheap voltage converter and wiring it in as a turbo switch, no idea how effective it is but I guess it's the only way to get a boost without one of these controllers or a higher voltage battery
A lesser version of 'field weakening' exists and is known as 'overspeed' or 'timing advance'. Similarly to field weakening, it provides a way to overcome the natural BEMF, but does so in a cruder manner and does not require an even more costly FOC (field oriented control) controller.
The cheapest non-FOC controllers that I am aware of which feature a timing advance are made by powervelocity.com, although I don't think they have anything available under £200.
The cheapest non-FOC controllers that I am aware of which feature a timing advance are made by powervelocity.com, although I don't think they have anything available under £200.
I guess that puts the extra cost of a Phaserunner controller in perspective with it being FOC. Have you tried out one Danielrlee?
No, I haven't tried one myself, but I've only heard good things about them. My biggest issue with the Phaserunner is the 90A peak phase current limit, far lower than I tend to run nowadays. I'd consider one for use with my BBSHD FS build if the controller ever fails though.
I've had my eye on the following controller series, which has been in development for a while now. I'm fairly certain it's what I'll opt for with my next build:
https://endless-sphere.com/forums/viewtopic.php?f=31&t=75494
FYI, this is the cheapest way to obtain a Phaserunner that I am currently aware of - £229.00 delivered, UK stock:
https://electroncycles.co.uk/product/grin-phaserunner-electric-bike-field-oriented-waterproof-motor-controller-30v-90v-50a/
https://electroncycles.co.uk/product/grin-phaserunner-electric-bike-field-oriented-waterproof-motor-controller-30v-90v-50a/
Thanks Daniel, yes I'd spotted Electron had them and thought the price was better than import from Grin Tech. i'm dreaming a bit at the moment, but would deff. like to venture into the higher tech stuff in the future. I had same idea of trying one out on my HD, but also think I would need to up my current battery voltage, 52v, to get a decent result. More £££'s than I have at the moment.
BTW, those controllers in your link look very capable and well constructed, even to my untrained eye. My desire to learn more about these higher powered controller systems is deff. helped by this type of product. More reading on ES needed
it's not something that I would want to buy or sell, but I am curious about why you want that feature? As far as I can see, these controllers 'detune' the phase of the current to reduce the magnetic flux, the effect is similar to when you go from motor winding code 11 for example to winding code 9, you get more RPM per volt. The downside is you waste more battery.
Wouldn't better to choose a motor with a slightly lower winding code?
Wouldn't better to choose a motor with a slightly lower winding code?
I don't understand it well enough to comment Woosh, but are you saying field weakening uses additional battery power?
The beauty of field weakening is that efficiency is only affected whilst the magnetic flux is weakened. Below these speeds, the controller behaves as normal.
Swapping the motor for a higher kV motor, or raising the system voltage would move the efficiency curve across the board.
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Yes, current increases during flux weakening in addition to the extra current required to reach those higher speeds. Field weakening definitely requires a stiff battery.
Thanks Daniel, yes it makes sense that field weakening mode needs additional power to take effect, but as you say it only takes effect when max.revs is reached. Similar effect to a temp. increase in voltage, which is what anon4 mentioned , using a voltage converter, but I can't see this working on high amperage systems.
I have another idea... I have my old Carrera battery sitting here, works just fine. If I ran some lines from the main power line into my panniers and kept that battery there maybe I could use it as backup, or more excitingly as a booster? I probably would need a beefier controller to handle an extra 36v, and would probably be pushing my luck. Mainly though I'd use for extra range, just mega turbo when I sleep in for work could be handy
Overlooking the issues of connecting your packs in series for one moment, I doubt that your Carrera battery would be able to sustain the continuous output required to reach the sort of speed increase you are talking about. What is the other battery pack that you own?I have another idea... I have my old Carrera battery sitting here, works just fine. If I ran some lines from the main power line into my panniers and kept that battery there maybe I could use it as backup, or more excitingly as a booster? I probably would need a beefier controller to handle an extra 36v, and would probably be pushing my luck. Mainly though I'd use for extra range, just mega turbo when I sleep in for work could be handy
If you want high speed on the road there is a solution, it is called a vélomobile. Remember Colin Chapman? At a time when people were throwing huge amounts of power into cars to go fast he removed weight. E-bikes are light enough to go very fast with little power if they are in a vacuum, air resistance is holding them up. A vélomobile removes air resistance to a very large degree.
A 250 W nominative i.e. legal pedelec motor is capable of pushing a vélomobile at 60 km/h average speed on the flat without one needing to pedal. Chuck a 750 W motor in and you can cruise all day at 75 km/h which is about the average speed of a car on normal roads. If you do pedal along you will be sipping Amps from the battery.
In normal conditions (hills, wind, traffic...) a legal e-vélomobile (250 W nominative, 25 km/h cut off) is able to maintain average speeds around 45 km/h. A member of this forum of a certain age rides his Quest at 45 km/h without a motor.
A 250 W nominative i.e. legal pedelec motor is capable of pushing a vélomobile at 60 km/h average speed on the flat without one needing to pedal. Chuck a 750 W motor in and you can cruise all day at 75 km/h which is about the average speed of a car on normal roads. If you do pedal along you will be sipping Amps from the battery.
In normal conditions (hills, wind, traffic...) a legal e-vélomobile (250 W nominative, 25 km/h cut off) is able to maintain average speeds around 45 km/h. A member of this forum of a certain age rides his Quest at 45 km/h without a motor.
Nah I realise it's probably a bad idea, but might still add lines and connectors for using it as a backup battery. I realize that you can't just hook it up that way safely. My other battery is a 48v hailong 13ah, Chinese cells, supposedly good for 25a continuous
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