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Old 01-17-2003, 01:00 PM   #16
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Really nice work.

What happen at almost full throttle? I assume, that even at low frequency, the reverse pulse will last into the next pulse?

I agree, that the Schotky diode conduct the reverse voltage pulse, but I highly disagree that this leads to reduced effiency at higher frequencies. Cause: When the reverse voltage are conducted by the diode, then (seen from the motor point of view) it is close to dead short the motor. This actually means braking....

Besides, it seems that almost everyone, both racers and companies, agree, that higher DF equals smoothness AND more runtime, while lower DF equals more unch, but less runtime.

However, this is nice work. Two things came to mind: Phases and the relation between motor frequency and ESC frequency.

Phases: This is an area I dont know much about, but the motor is basically three coils. A coil in itself is very different to a resistor. In addition, there's 3 off them, which shift at some frequency. At 30.000 RPM, the coils shifts 500 times pr. second. If I'm correct, this result in a frequency of 1.500 HZ.

A motor like this, are basically designed for DC. With an ESC, we operate it with pulses.

Therefor I assume, that the relation between ESF frequency and motorfrequency plays a role: If the ESC DF are low, then it's closer to DC....
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Old 01-17-2003, 01:59 PM   #17
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"What happen at almost full throttle? I assume, that even at low frequency, the reverse pulse will last into the next pulse?"

At full throttle the power pulses are wider (longer in time). They merge. There is no useful recirculating current. At 3/4 throttle the pulses are quite wide so there is little time for the recirculating current to work effectively.

"I agree, that the Schotky diode conduct the reverse voltage pulse, but I highly disagree that this leads to reduced effiency at higher frequencies. Cause: When the reverse voltage are conducted by the diode, then (seen from the motor point of view) it is close to dead short the motor. This actually means braking...."

Although the voltage reverses during recirculation, the current continues in the same direction driving the motor for free. It is not braking.

"Besides, it seems that almost everyone, both racers and companies, agree, that higher DF equals smoothness AND more runtime, while lower DF equals more unch, but less runtime."

I aggree that higher frequencies yield more smoothness. A couple of racers tested lower frequencies with a 10/2 in a touring car and got more runtime. This was during a thread on this subject on Trinities Tech Talk.

I have seen some discussion matching the speedcontrols frequency to the motor. I believe LRP does this in a way by changing frequency with motor speed. The only problem is the speed control does not know what wind you are running. I do this when I use a higher frequency for mod. A 10/2 has much less induction than a stock motor so the recirculating pulses are briefer.

The coils are inductors and have properties of inductors.
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Old 01-17-2003, 02:02 PM   #18
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Default Driving Technique for Max Efficiency

You get increased efficiency by using the recirculating current effectively. The way to do this with a mod motor is to gently apply the throttle and keep your trigger just ahead of the car's speed rather than jamming the trigger to full throttle right after the corner. This increases the time that you are at part throttle and utilizes the free recirculating current effectively.
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Old 01-17-2003, 06:31 PM   #19
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i have a Keyence V zero xtreme esc and i played around with the ESC frequency once 2 test it b4...

a lower frequency would provide more punch,but ur power band will not b smooth n from my testing,initial response of the car is slow,but then the torque will sudden jus kick in...sort of like turbo lag...

with a higher frequency,the power band of the car is smoother and car feels better for mi...
hmmm,...more heat is also generated with a higher power band...
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Old 01-17-2003, 08:05 PM   #20
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One thing that I don't think has been mentioned in this thread is the efficiency of the speed control itself. I did testing on a keyence speedo which has the ability to show you the temperature of the FET's. The higher the frequency, the hotter the FET's get. Just running between 7,500 and 20,000 hz settings, I experienced almost 20 degrees difference in operating temperature. Obviously heat can equate to a loss of efficiency. I'm not saying high frequencies are bad but just something to consider.
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Old 01-17-2003, 08:33 PM   #21
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hm..... turbo lag ..... i also use keyence but i only have turbo lag IF i set the frequency too high and the inital trottle point too low ...
once i set it to my liking its linear .....
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Old 01-18-2003, 07:53 AM   #22
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using an ESC with low drive frequency( ard 1khz) and it's really punchy...to the extent that i'm seriously thinking of reusing my standard diff's instead of a one-way...but after hearing about this efficiency thing i dont think it's that bad now with the extra punchiness....BTW any way's to help control the punch?
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Old 01-18-2003, 08:10 AM   #23
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You could look into the settings on your radio, I kow my KO has a featre that allows me to slow down how fast the ingagment of my throtte and steering inputs are to allow you to be "jerkier" but still get smooth inputs....... Might be worth a try if you use a high end radio......
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Old 01-18-2003, 08:25 AM   #24
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any other ways?like on the car itself?cos i dont have a high end radio..
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Old 01-18-2003, 08:31 AM   #25
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You can control the punchiness a bit with gearing that detunes the car a little. Either a little too high (bigger pinion) or a little too low will slow the car a bit and reduce the punch. Be careful not to overgear so much that the motor gets too hot.
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Old 01-18-2003, 08:36 AM   #26
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thanks..have already thought of that...just needed someone to nudge me a little
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Old 01-18-2003, 08:58 AM   #27
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u can use current limiter or power limiter also...
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Old 01-18-2003, 09:08 AM   #28
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well....it's a cheap ESC with no power pot or any such..to tell the truth the brakes suck as well.wish i can hurry the ships or something so my V7.1 arrives soon
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Old 01-18-2003, 03:03 PM   #29
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increase the motor timing,

this wil give you higher RPM but lower bottom end torque.

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Old 01-18-2003, 04:03 PM   #30
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punchy..... hm... why i just cant get enuff punch when pple are saying thay have too much ....
my settings on esc and radio are on the comical side of punchiness.....

inital drive power is at 35
freq is at 0.7
trot limitor at 0
trot curve on transmeter(ex1 mars) at 100
inital trot in controler is at 45L 70M

anything else i missed out?
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