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Old 05-29-2008, 04:56 PM   #1
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Default Sensored vs. Sensorless

What is the difference between the sensorless motor and the sensored motor?

What are each type's advantages/disadvantages and uses (which classes)?
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Old 05-29-2008, 04:59 PM   #2
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In a sensored motor, the esc always knows where the rotor is inside the can, sensorless, it basically takes it best guess.

Around this area, we have found sensorless has no real advantages. Unless you like the exclusive push start system.
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Old 05-29-2008, 05:19 PM   #3
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The sensored motor has sensors in it to tell the ESC what position the rotor is in. A sensorless motor it totally dependant on the ESC to guess what position the rotor is in. It is worthy to note that a sensored motor can be used for both types of ESCs but a sensorless motor can only be used with a sensorless ESC. Some claim that sensorless is more effecient and has a bit more power then sensored. Personally I don't know if that is true or not. The only advantage I can attest to is the reduced wire clutter since you don't use the sensor wire harness on a sensorless ESC or motor.
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Old 05-29-2008, 05:56 PM   #4
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I've heard that sensorless can achieve higher RPM with a slight advantage in efficiency, but for racing Sensored is the way to go since racing is about constant accelleration, not TOPSPEED. With a sensored motor, the ESC knows the rotor posistion and should not faulter under hard accelleration. Sensorless have been know to "cog" under accellerations and sometimes spin backwards from a standing start.

I think the efficiency of the system has is also based on the winding type. Either system can use either winding. Delta (IMO Dasiy Chain Windings) and "Y" or wye (IMO Star Windings). The Delta windings are better for RPM. While the "Y" is better for torque. The efficiency from wye windings comes from the windings not being able to carry current once the phase is no longer powered thus not taking in power in the off state.
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Old 05-30-2008, 04:48 AM   #5
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Quote:
Originally Posted by trailranger View Post
I've heard that sensorless can achieve higher RPM with a slight advantage in efficiency, but for racing Sensored is the way to go since racing is about constant accelleration, not TOPSPEED. With a sensored motor, the ESC knows the rotor posistion and should not faulter under hard accelleration. Sensorless have been know to "cog" under accellerations and sometimes spin backwards from a standing start.

I think the efficiency of the system has is also based on the winding type. Either system can use either winding. Delta (IMO Dasiy Chain Windings) and "Y" or wye (IMO Star Windings). The Delta windings are better for RPM. While the "Y" is better for torque. The efficiency from wye windings comes from the windings not being able to carry current once the phase is no longer powered thus not taking in power in the off state.
I think you're a bit confused. There are no coggings under acceleration in sensorless. The only issue you can get is at the start. Any cogging once the car has started is not due to it being sensorless.

Also a common mistake is to think that with sensored the speedo always knows the exact position of the rotor, that is only true at standstill, once spinning the speedo is always late compared to the rotor, for physical reasons. This is why sensored systems use as much as 30 degrees worth of timing, otherwise they'd get negative timing at top speed. The downfall is that at low speed they are highly inefficient.

Also Delta provides less RPM than Y.
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Old 05-30-2008, 06:04 AM   #6
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Quote:
Originally Posted by TRF415boy View Post
I think you're a bit confused. There are no coggings under acceleration in sensorless. The only issue you can get is at the start. Any cogging once the car has started is not due to it being sensorless.

Also a common mistake is to think that with sensored the speedo always knows the exact position of the rotor, that is only true at standstill, once spinning the speedo is always late compared to the rotor, for physical reasons. This is why sensored systems use as much as 30 degrees worth of timing, otherwise they'd get negative timing at top speed. The downfall is that at low speed they are highly inefficient.

Also Delta provides less RPM than Y.
A 3T D will have a higher Kv then a 3T Y.

One example are the following:

https://shop.graupner.de/webuerp/servlet/AI?ARTN=97224
https://shop.graupner.de/webuerp/servlet/AI?ARTN=97225

The 3.5T Y has a 8800Kv and the 6T D has an 8800Kv, if the 6T D was a 3T D it would have around 16,000Kv.
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Old 05-30-2008, 06:15 AM   #7
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Quote:
Originally Posted by lutach View Post
A 3T D will have a higher Kv then a 3T Y.

One example are the following:

https://shop.graupner.de/webuerp/servlet/AI?ARTN=97224
https://shop.graupner.de/webuerp/servlet/AI?ARTN=97225

The 3.5T Y has a 8800Kv and the 6T D has an 8800Kv, if the 6T D was a 3T D it would have around 16,000Kv.
That's where you're wrong, we're talking equivalent windings here, and the equivalent in delta of a 3.5T Y would be a 7T, NOT a 3T. You cannot compare the power of a 3.5T Y and a 3T delta at all.
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Old 05-30-2008, 07:15 AM   #8
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I have run both systems. While sensorless systems are much better than before with the newer software updates..........they offer no where near the control and feel of a sensored system. I will never go back to sensorless. Just mu opinion.

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Old 05-30-2008, 07:36 AM   #9
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The "problem" of using sensorless hapen when you are using motors and esc of different brands.

Manufacturers are just learning about brushless and for now only dedicated (same manufacturer) equipment work well with another.

This is no different of what hapened some year ago with model airplanes motors and esc. Now every motor work well with every esc.

There will come the time when that will hapen with model cars motors and esc.

Beside that the systems work fine sensored or sensorless. Usually i use a Mamba Max esc and Mamba motors (sensorless) and the system is fantastic, you see no diference for any sensored system. I have tried in some races the MM esc and a GM Evo 3 motor and some cog can hapen in the start, some times it doesn't star at the moment, during the race I have no problems. I have tried the new SpeedPassion GT esc with Mamba motors, they work fine, and the GT esc with GM Evo 3 motor, where some dificult at the star can hapen but works fine with the sensors plugged.

I have tried the GM Evo3 motor with the GM Genius esc without the sensors and they work fine too.

So what i concluded, is that if esc and motors are from the same manufacturer they will work fine if sensorless. If you try to use esc and motor sensorless from different manuf. problems can hapen. The way to overcome those problem with diferent manuf. material have been to plug the sensors cables.
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Old 05-30-2008, 08:09 AM   #10
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Quote:
Originally Posted by TRF415boy View Post
That's where you're wrong, we're talking equivalent windings here, and the equivalent in delta of a 3.5T Y would be a 7T, NOT a 3T. You cannot compare the power of a 3.5T Y and a 3T delta at all.
How can I be wrong? You mentioned Delta provides less RPM than Y, but you didn't state anything else. So I only assumed you meant the same number of turns. A Delta wound motor will get to it's top RPM faster and a Y will get more torque, it's just the nature of how the windings make the motor react. If you really want to go into details, there are some engineers in rcgroups.com that can fill in all the details.
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Old 05-30-2008, 08:28 AM   #11
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Quote:
Originally Posted by TRF415boy View Post
That's where you're wrong, we're talking equivalent windings here, and the equivalent in delta of a 3.5T Y would be a 7T, NOT a 3T. You cannot compare the power of a 3.5T Y and a 3T delta at all.
Yes and no. Actually youre right but for comparing delta and star wound you have to use a factor of 1.73 what means a 6T is an equivalent to 3.5T. There had been 4T motors some time ago, but actually these were 7T deltas.
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Old 05-30-2008, 09:13 AM   #12
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All technical discussion aside, it goes like this:

Sensorless is good, cheap speed. It has poor throttle feel at low RPM's. It's good for bashing, or "racers" that are delusional about the importance of throttle control. It seems to work better in low turn motors (mod) than the higher turn motors ("stock").

Sensored is equally good, perhaps more expensive, and has a vastly superior throttle feel, especially lower in the power band. This is the only choice for serious racers.

Is most industry applications, sensorless appears to be the preferred method. It seems to be considered a newer, superior technology with less complicated ESC's. For toy car racing, however, sensored has established itself as king.
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Old 05-30-2008, 09:39 AM   #13
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Quote:
Originally Posted by V12 View Post
There had been 4T motors some time ago, but actually these were 7T deltas.
Is this true for all 4.0 motors? or just GM ones? Im asking because i have a 4.0 from Orion. If i got things right about delta motors i should lower even more the timing on the motor for it to work properly with my LRP TC...
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Old 05-30-2008, 09:47 AM   #14
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If you are going to do any type of racing, use a sensored competition legal motor.

Last edited by Rick Hohwart; 05-30-2008 at 10:12 AM.
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Old 05-30-2008, 09:59 AM   #15
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...

Last edited by syndr0me; 05-30-2008 at 11:07 AM. Reason: Fixed typo
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