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[RNM]

in fact the Sevcon Gen4 does provide full current at 0RPM,

If people are complaining that the bike is slow at very low speeds, I think the ESC is not providing full torque at 0rpm.
Can the Sevcon do that? Perhaps.

Another place to look for answers is the MBB settings (Main Bike Board):
http://electricmotorcycleforum.com/boards/index.php?topic=2925.0
http://electricmotorcycleforum.com/boards/index.php?topic=4357.0

Good luck guys! 

[Mr. Fusion]

The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill

Lecram, it's a limitation of the ESC. Full current (full torque) at 0 rpm would induce great current ripple because the BEMF is very low. To have full current, you would have to increase ESC switching freq a LOT, but that means a lot of additional heat (=burned MOSFETs)

Actually the BEMF voltage doesn't have an influence on the current ripple. Only the motor (winding) inductance does. The very low BEMF just means that a lot of current is needed to get some active power. But from the ESC limitations still full torque should be available...
Thus I also think it's rather a configuration limitation.

[RNM]

The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill

Lecram, it's a limitation of the ESC. Full current (full torque) at 0 rpm would induce great current ripple because the BEMF is very low. To have full current, you would have to increase ESC switching freq a LOT, but that means a lot of additional heat (=burned MOSFETs)

Actually the BEMF voltage doesn't have an influence on the current ripple. Only the motor (winding) inductance does. The very low BEMF just means that a lot of current is needed to get some active power. But from the ESC limitations still full torque should be available...
Thus I also think it's rather a configuration limitation.

BEMF voltage does influence current ripple
The formula is V= L di/dt
http://en.m.wikipedia.org/wiki/Inductance

In this case, V (applied to the motor winding) = V(battery) - V(BEMF). If "dt" and "L" are constant (constant switching frequency= constant dt and L is constant), then "di" varies with V, which varies with V(BEMF).

0 rpm => 0 V(BEMF) => max "V" => max "di" => possibility of lower phase current => lower standstill torque


But I agree that a possible configuration limitation might exist.

[Doug S]

RNM, at low switching speeds, the DC resistance of the copper windings dominates the inductance in limiting how much current you can drive through the motor; at some transition speed, inductance becomes a factor and you can no longer get maximum current through the windings (or, stated equivalently, BEMF starts to rise), which reduces the torque the motor can put out. That's called the "field weakening" point; IIRC it occurs around 3500 rpm on my bike (a 2014 SR), which is somewhere around 60 mph. BEMF is not a factor at low speeds, DC resistance of the copper wire is.

[RNM]

RNM, at low switching speeds, the DC resistance of the copper windings dominates the inductance in limiting how much current you can drive through the motor; at some transition speed, inductance becomes a factor and you can no longer get maximum current through the windings (or, stated equivalently, BEMF starts to rise), which reduces the torque the motor can put out. That's called the "field weakening" point; IIRC it occurs around 3500 rpm on my bike (a 2014 SR), which is somewhere around 60 mph. BEMF is not a factor at low speeds, DC resistance of the copper wire is.

DC winding resistance is another component of the motor time constant (L/R), which let's us calc the current rise and fall.
See the spreadsheet in this link:
http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=29852&start=15#p433095

2 notes for the spreadsheet:
- Time constant varies a lot from motor to motor
- "Applied Voltage" on the top-left is the V (motor) = V (battery) - V(BEMF)

If you play a bit with it, you can see that having 0 BEMF or 50V BEMF, with a 100V battery , you get twice the current in the same time interval.

[M@2015DS]

I stand corrected Ted. Must have been looking at one of the V6 specs.

[joystix2]

I recently noticed my SR would start slowly off the line but after a second or two then it would take off.... Through the App I put everything thats on CUSTOM mode to 100% except the coasting regen to 0%... I noticed a lot more torque off the line in the new Custom mode, even more THAN Sport mode...... Im wondering if if I accidentally lowered the numbers in SPORT mode that I didnt know I did or could do? 

[kensiko]

Lecram  you'll need a DSR