1LikesTiming vs. Power (Brushless)
12-05-2007, 08:34 PM
#1
Timing vs. Power (Brushless)
There has been thoughts for a long time, in a lot of peoples mind with the old BRUSHED motors that MORE timing equals FASTER motors...
I hear a lot now with brushless in a similar direction...
Some people I have talked to have theirselves so worried up about this issue that even though they have NEVER run a Brushless motor...the idea sombody might have one with MORE timing is making them sick to their stomach.
Then through the ESC's into the mix and that you can change or add even more timing through programming...now they are really upset.
So WILL a Higher Timed Motor go FASTER than a LOWER timed motor?
and can ANYBODY answer that question not having any other information?
Personally, I say...two motors with EQUAL 'POWER' should run the SAME top speed....but the motor with MORE timing may have a different curve in getting there.
Now...that doesn't mean the two would accelerate the same - so a LOWER timed motor may be better for LONG straights - where a higher timed motor may be better for "Off the Corner" speeds?
Any thoughts
I hear a lot now with brushless in a similar direction...
Some people I have talked to have theirselves so worried up about this issue that even though they have NEVER run a Brushless motor...the idea sombody might have one with MORE timing is making them sick to their stomach.
Then through the ESC's into the mix and that you can change or add even more timing through programming...now they are really upset.
So WILL a Higher Timed Motor go FASTER than a LOWER timed motor?
and can ANYBODY answer that question not having any other information?
Personally, I say...two motors with EQUAL 'POWER' should run the SAME top speed....but the motor with MORE timing may have a different curve in getting there.
Now...that doesn't mean the two would accelerate the same - so a LOWER timed motor may be better for LONG straights - where a higher timed motor may be better for "Off the Corner" speeds?
Any thoughts
12-05-2007, 09:04 PM
#3
There has been thoughts for a long time, in a lot of peoples mind with the old BRUSHED motors that MORE timing equals FASTER motors...
I hear a lot now with brushless in a similar direction...
Some people I have talked to have theirselves so worried up about this issue that even though they have NEVER run a Brushless motor...the idea sombody might have one with MORE timing is making them sick to their stomach.
Then through the ESC's into the mix and that you can change or add even more timing through programming...now they are really upset.
So WILL a Higher Timed Motor go FASTER than a LOWER timed motor?
and can ANYBODY answer that question not having any other information?
Personally, I say...two motors with EQUAL 'POWER' should run the SAME top speed....but the motor with MORE timing may have a different curve in getting there.
Now...that doesn't mean the two would accelerate the same - so a LOWER timed motor may be better for LONG straights - where a higher timed motor may be better for "Off the Corner" speeds?
Any thoughts
I hear a lot now with brushless in a similar direction...
Some people I have talked to have theirselves so worried up about this issue that even though they have NEVER run a Brushless motor...the idea sombody might have one with MORE timing is making them sick to their stomach.
Then through the ESC's into the mix and that you can change or add even more timing through programming...now they are really upset.
So WILL a Higher Timed Motor go FASTER than a LOWER timed motor?
and can ANYBODY answer that question not having any other information?
Personally, I say...two motors with EQUAL 'POWER' should run the SAME top speed....but the motor with MORE timing may have a different curve in getting there.
Now...that doesn't mean the two would accelerate the same - so a LOWER timed motor may be better for LONG straights - where a higher timed motor may be better for "Off the Corner" speeds?
Any thoughts
BL motors have a lot of variables. Rotor OD, Rotor length, Stator ID, stator length, wind, wire gauge, wire material grade, stator steel grade, rotor magent grade, manufacturing process, it goes on and on...
Every combination of variables will have a timing level that will produce the most power. That will be the right timing. Its up to the motor manufacturer to figure this out and get us started in the right direction.
Increaing timing affects 3 things. It will increse RPM, increase amp draw and increase heat. If you increase timing and you go faster it was a good move. If you increase timing and you go the same speed and the motor runs hotter it was a bad move.
Some motors like LRP, GM/Orion and Novak have adjustable timing rings. Moving the ring moves the hall effect sensor that determines rotor position in relation to the windings. This makes the speedo fire the windings in the stator further in advance of the rotor pole.
Some motors like the new Faigao/SpeedPassion motors are not adjustable...but the Faigao/SpeedPassion speedos are. You can advance or retard the timing of the motor at the speedo. It does the same thing as moving the hall effect sensor but it does it electronically.
There is going to be a lot of things figured out with BL over the next few years. We litterally are at the same point, relatively speaking, as when we switched from wiper speed controls to the first ESC's in the mid 80's.
12-05-2007, 09:42 PM
#4
i've played with timing on my novak 10.5 and 13.5. as timing was advanced or retarded, the powerband basically shifted around a bit and I had to gear to compensate. lap times are essentially the same once the gearing was optimized.
with the 13.5 i've played around with rotor size as well as timing. with the small rotor the motor was more of a top end motor, with the larger rotor it's more of a low end motor. ultimately, after getting brave with the gearing of the small rotor, i can turn the same laps and get a similar feel between the two setups.
with the 13.5 i've played around with rotor size as well as timing. with the small rotor the motor was more of a top end motor, with the larger rotor it's more of a low end motor. ultimately, after getting brave with the gearing of the small rotor, i can turn the same laps and get a similar feel between the two setups.
12-09-2007, 08:06 PM
#5
Advancing the timing beyond the nominal optimum point can be done for two reasons:
1) Adjusting for the shift in the permanent magnet field that occurs during operation at higher torque levels. This is normally only a few degrees or so when using rare-earth materials and relatively few pole pairs (as is the case with the typical single-pole-pair brushless RC car motor), and ideally it's mapped to the actual winding current. Old-school brushed motors with their relatively weak ferrite magnets required a lot of advance just to offset the amount of distortion in the induced field.
2) Field weakening at higher speeds. Rather radical amounts of advance (45-70 degrees) applied at speeds above the normal max speed of the motor can provide some intentional (and temporary) demagnetization of the permanent magnet, with a corresponding increase of Kv and decrease of Kt. It's possible to more than double the base speed of a motor by applying this technique, but it's not simple or easy to do without characterization of several variables, and the transition into field weakening must be done very carefully to avoid overmodulating the motor.
I haven't mapped out the advance curves of any RC car controllers, but I suspect that the maximum advance available on them probably is too much to fulfill the needs of purpose #1, and not quite enough to accomplish purpose #2.
1) Adjusting for the shift in the permanent magnet field that occurs during operation at higher torque levels. This is normally only a few degrees or so when using rare-earth materials and relatively few pole pairs (as is the case with the typical single-pole-pair brushless RC car motor), and ideally it's mapped to the actual winding current. Old-school brushed motors with their relatively weak ferrite magnets required a lot of advance just to offset the amount of distortion in the induced field.
2) Field weakening at higher speeds. Rather radical amounts of advance (45-70 degrees) applied at speeds above the normal max speed of the motor can provide some intentional (and temporary) demagnetization of the permanent magnet, with a corresponding increase of Kv and decrease of Kt. It's possible to more than double the base speed of a motor by applying this technique, but it's not simple or easy to do without characterization of several variables, and the transition into field weakening must be done very carefully to avoid overmodulating the motor.
I haven't mapped out the advance curves of any RC car controllers, but I suspect that the maximum advance available on them probably is too much to fulfill the needs of purpose #1, and not quite enough to accomplish purpose #2.
12-10-2007, 06:59 AM
#7
with the Orion motors about 1mm timing(=about 3 degrees of timing) is the sweet spot. The motor has a little more RPM and the heat is not an issue, any more timing than 1mm advanced timiing and its just making the motor run hotter without anymore performance gain.
12-10-2007, 03:41 PM
#8
Since torque is directly proportional to current draw, it should be possible to add timing accordingly - either by direct measurement of current, or by using the motor speed and ESC modulation index (PWM duty cycle) along with characterization of the motor (mainly the Kv constant and resistance) to estimate the current draw. I'm not aware of any RC controllers that do this.
12-10-2007, 03:45 PM
#9
If you run enough timing to put the motor into a field-weakened state, then you'll need to gear down slightly to compensate for the trade-off of less torque for more speed. This is why mechanical means of adjusting timing in a brushless motor is nowhere close to optimal - it should be done in the ESC in a way that allows the timing to be advanced only at higher motor speeds.
12-10-2007, 04:24 PM
#10
Since torque is directly proportional to current draw, it should be possible to add timing accordingly - either by direct measurement of current, or by using the motor speed and ESC modulation index (PWM duty cycle) along with characterization of the motor (mainly the Kv constant and resistance) to estimate the current draw. I'm not aware of any RC controllers that do this.
12-10-2007, 06:39 PM
#11
I too, have been amazed at people who get so worked up about timing, even those that haven't even run brushless. I feel that a lot of these concerns aren't really true fears. Instead, it's an opportunity for some veteran brushed tuners to spread rumors in hopes to hang on to their brushed racing a little longer. I suppose I can understand somewhat. After all, they are slowly losing their brushed tuning advantage over the average brushed racer. It took me over a year of experience and research to become a good brushed tuner.
But I've said it before, and I'll say it again. You can advance or retard the timing (on the brushless ESC or brushless motor) until you are blue in the face. The electromagnetic coil field strength will only generate so much Watts of power out of the motor, at a given voltage. There is a point where it simply will not get any better. That's the law's of physics at work. Sleep better my friends, you can't cheat physics.
As of today, sure, their might be a little room to find the perfect timing, or a speed controller that may do some variable timing better than others. But the big picture is, when the right timing is used, there is nothing more you can do. Your limited by the electromagnetic coil field strength.
But I've said it before, and I'll say it again. You can advance or retard the timing (on the brushless ESC or brushless motor) until you are blue in the face. The electromagnetic coil field strength will only generate so much Watts of power out of the motor, at a given voltage. There is a point where it simply will not get any better. That's the law's of physics at work. Sleep better my friends, you can't cheat physics.
As of today, sure, their might be a little room to find the perfect timing, or a speed controller that may do some variable timing better than others. But the big picture is, when the right timing is used, there is nothing more you can do. Your limited by the electromagnetic coil field strength.
12-10-2007, 06:50 PM
#12
But I've said it before, and I'll say it again. You can advance or retard the timing (on the brushless ESC or brushless motor) until you are blue in the face. The electromagnetic coil field strength will only generate so much Watts of power out of the motor, at a given voltage. There is a point where it simply will not get any better. That's the law's of physics at work. Sleep better my friends, you can't cheat physics.
As of today, their might be a little room to find the perfect timing, or a speed controller that may do some variable timing better than others. But the big picture is, when the right timing is used, there is nothing more you can do. Your limited by the electromagnetic coil field strength.
12-10-2007, 06:52 PM
#13
The Mamba doesn't require the user to enter any basic motor parameters, so I'm skeptical of its ability to correctly add timing with increasing speed and/or torque (that's not to say it's a bad controller - I have a couple and they work great).