Another good one

Another great video!

@RCexplained

5 жыл бұрын

Thank you!

Good practical measurement. Thank you. One comment: even though voltage across the battery leads is not going to drop significantly, I would put a voltmeter across the battery. This, of course, becomes more important if you have load on the motor.

Hey brother, again, love and appreciate these videos immensely. So I think I'm finally starting to put it all together, but then, ultimately, I know that I still have no idea because of my limited understanding of what is essentially the most important component and barometer, power output. For all intents and purposes, I think there's perhaps some merit to thinking about a BLDC motor relative to an ICE motor with KV having a direct, albeit inversely proportional, relationship to displacement with the actual windings perhaps akin to Redline (a 6.0 liter American v8 historically makes good low end and mid range power but revs out at less than 6k rpm [i.e. a 4480 800kv motor] whereas a 3.0 liter v12 from Italy makes its power at the top of the rev range and winds out to 8500rpm [i.e. a 4074 2650kv motor]. So even though both of these imagined engines make 400hp, their driving characteristics and how they achieve said power would make them feel and perform vastly different. So there are a few things that seemingly always trip me up: Why are manufacturers seemingly so reluctant to broadcast the power output of their BLDC motors. If someone is building a gas go cart, the hp rating of the engine is one of the first decisions and defining characteristics (however It just occured to me that this is definitively only with 4 stroke engines with 2 stroke engines, like BLDC motors, using only their size to define each with the HP rating often buried deep in the manual, if available at all....oh the catharsis of writing...so maybe aligning BLDC motors more specifically with 2 stroke motors might be more beneficial) Man oh man, so If youre even still reading this, I guess my question ultimately boils down to how is the watt output of a motor determined and what value should we place on that number? Should that be a major consideration in our motor choice? Lastly, in one of my cars, I have a 2200kv 4074 motor rated at 1600watts with a 4s 86A max. Running this motor on 4s, my power meter or the data logged (Im using a castle mamba x esc) have shown that the motor pulled all 86A but the output never exceeded 1250w. That's a pretty significant discrepancy . What might cause that? Can you please perhaps either point me in the right direction with reading material to better grasp how much power BLDC motors make, make a video on the topic, or respond to this chaotic mess of a post? Thanks brother and my inability to distill my lacking understanding only further corroborates how lacking that understanding is...ha, thanks man.

@RCexplained

4 жыл бұрын

Hey Samm, Not sure how I missed replying to comments on this specific video. I did a brushless motor comparison to ICE. DId you see this? What voltage did you run to the motor that made 1250watts pulling 86A?

@Jdogdrums7

3 жыл бұрын

14.8v times 86a ~ 1273 amps Even a fully charged 4s at 16.8 volts multiplied by 86 amps is still only 1445 amps If you want full 1600 watt power out of your motor, you need to increase the speed of the motor, which will increase the amp draw for a given load. If you are already maxing out your ESC's speed capability, then you need more load on the motor at a given speed to increase amp draw. The only other thing you could do is to increase voltage to the motor, but be careful not to exceed the rated voltage of your components. TL;DR - you need to pull or allow the motor to consume more amps to achieve 1600 watts at the 4S voltage.

On an SEDF setup, regarding Low Timing, would it be problematic if the voltage is considerably higher than factory stock (14S vs 12S) using the stock 12 bladed rotor. How do we make sure that we dont blow our load too early?

Thank you so much for your video, I loved it. May I know what is the power required to move a vehicle of 180kg with solar panels, about 15 kmph.

@RCexplained

5 жыл бұрын

Thank You for your comment! To answer your question, it does highly depend on the type of hull that you have. If you have a planing hull, it will be easier to get to speed. I would expect that you should start with 4kw and adjust from there. I have been able to get a planing hull to 30km/h with a 225kg weight.

A 3 phase brushless motor has the following values. The maximum current drawn from the battery is 4.62 amps.. The thrust is 4025 grams with a three-bladed fan 18 * 8.. The speed at the maximum lifting force is 2780 rpm. The battery voltage is 23.46 volts. How much is the output power? How much is the efficiency?

Great explanation videos!!! I have a quick question.... What kind of no load current would you expect to see on a 190KV 6368 brushless dc motor running at 36v ? I have found it impossible to find a data sheet and am worried I am about to fry my esc by running it.... I am trying to make a tennis ball machine so the loaded current shouldn't be much higher...? Many thanks!

@RCexplained

4 жыл бұрын

Hi Mathew, I would expect unloaded current to be around 5A or less. However, I would not be too concerned about unloaded current regardless of what it happens to be. My attention would be focused on loaded current. Loaded current is proportional to the load that you are placing on the motor. As load increases, current increases. This would entirely depend on your setup. You will have to accelerate your motor up to speed first. This will pull current. When operating, if you rely on a heavy mass to use inertia to help spit the tennis balls out, this will smooth out the loaded current during delivery. However, if you are no stop popping tennis balls out of the machine, inertia will get bogged down and the motor will be doing all the work.

How do I calculate load current in a shunt DC motor?

The specs sheet has 2.5A of No load current at 10V so if I want the value at 22.2V can I double it will it give the correct value ?

Hi Sir .I need to know why there will be fluctuations in no load current @ constant speed and constant voltage in bldc motors.. Please give me some answer

Well explained, For no-load condition increasing current at the same voltage will actually increase torque since more power is provided & we can reduce RPM that way as well?

@RCexplained

4 жыл бұрын

Thank you for your comment. I don't quite understand what you are getting at. How are you going to increase current at the same voltage? Or are you referring to a motor with a larger no load specification? The no load specification doesn't really tell you much about the torque output of the motor.

@skipper5811

4 жыл бұрын

@@RCexplained if you use a motor at 8A & 24V or 12A & 24V (assume you are a developer). Here no-load torque will simply increase as the magnetic flux produced will be higher

@RCexplained

4 жыл бұрын

@@skipper5811 yes, an increase of current produces more torque. This happens when the motor is loaded. No load implies no torque is produced.

@skipper5811

4 жыл бұрын

@@RCexplained But what in case of a BLDC motor? they always produce no-load torque. In actual no load term is inaccurate as there is always a load because of the rotor. if no torque is true than RPM should be able to go infinity.

@RCexplained

4 жыл бұрын

Hey Skipper Studio. Load is typically regarded in BLDC motors as external to the motor. Internal load is related to efficiency as in theory, following newtons first law, there should not be any load to keep a motor rotating. Since nothing is 100% efficient, this is where the No-Load (Io) value comes in. A high (Io) value on the motor, does not say much about the torque of the motor. But it does tell you that there is a lot of wasted power at high motor speeds. RPM of the motor is electrically limited by kv and voltage. Any type of load does not come in to the equation.

My 2500kv motor's idle current at 10V is 2.5A is there any mathematical way to assume the idle current at 22.2V can you please help me

Hello, i wanted to know how much current a brushless motor need or how to calculate it? 🤔

@RCexplained

4 жыл бұрын

Hi Gabriele 17, for RC airplanes there are online calculators that help out with this.

any ideal why different controllers/boards get different motor current (100mA ~400mA) to drive same BLDC motor?

@RCexplained

6 ай бұрын

No, in my testing the Io value has been within a very small margin of difference.

How to measure the current of each brushless motor in a drone under load?

@RCexplained

3 жыл бұрын

Easiest way to do this is to have an ESC that data logs the performance. Download the data from the ESC

Disregard most of the previous gobblygook and perhaps this is more of a question on the fundamentals of current than on BLDC motors specifically, but in the instance of let's say a 5870 motor by tp power, I dont understand how the same 16000w output can be achieved from the same can from 25v and 600a or 125v and 125a (in both cases, Im using figures that are close representatives but not specific). Is there anyway you point me in the right direction for reading material or other sources or even perhaps elucidate this yourself? Thank you again

@RCexplained

5 жыл бұрын

Hey! Thank you for your awesome question and comment. I think it would be best for me to answer these questions in a video. I can shift the next couple weeks video out and try and get these in this week. It may take 2 videos, one for a comparison of ICE vs bl motors and one talking about voltage, current and motor power from the same can.

@sdy5001

5 жыл бұрын

@@RCexplained that would be incredible, thank you. Learning new stuff, especially conceptual stuff, always came easy so I'm sure others are trying to sift through it all as well and it seems like such an integral part of the hobby and such an important aspect of so many of the technologies of the future I wonder why it's not more readily discussed. Hopefully your videos to come get a zillion views and get that ball rolling!

@xnoreq

4 жыл бұрын

@@sdy5001 Just a very rough calculation with TP5870 3D vs 10D: the former has high Kv (1690) which leads to a low torque constant. The total torque produced by the motor is the product of this constant and the current. The current specified by the manufacturer as 650 A. The latter has low Kv (540) which leads to a much higher torque constant. But now the max current specified by the manufacturer is much lower: 202 A. And this makes perfect sense. The low Kv motor has probably thinner wires with more windings increasing Rm (basically the resistance of the wire). Resistance reduces current draw, hence the need for higher voltage. The thinner wire / extra windings would also heat up more if you were to push higher currents through it, hence the lower current limit. So if you do the math you'll see that with max voltage/current you feed both with about 15 kW electrical power and get out of them roughly 14 kW mechanical power. But this is ONLY the case if your load (the propeller) is such that you achieve the numbers given by the manufacturer. A too large/small prop may completely ruin efficiency for either of the motors. Of course you also need the power supply that outputs the specified voltage AND can supply the current.

If I'm using 2s-12s motor at 6s instead of 12s so will it affect the power and torque of the motor?

@RCexplained

4 жыл бұрын

You are limiting the power potential by not using the full voltage potential of the motor.

@piyushtashildar3240

4 жыл бұрын

@@RCexplained thank you sir!! But what about the torque?

@RCexplained

4 жыл бұрын

@@piyushtashildar3240 Hi Piyush, the torque that the motor delivers is directly related to the load placed on to it. Load is related to the current. If you pull more current you will have higher torque output. Torque on 6s can still be the same as torque on 12s however, it will be a lot more difficult to produce torque at high RPM's on 6s.

Isn't the current from the battery pulse width modulated rather than DC?

@RCexplained

4 жыл бұрын

From the battery it is DC. It then is Pulse width modulated at the ESC and lastly electrically commutated in to AC power for the motor.

@gmack4097

4 жыл бұрын

@@RCexplained So there's enough capacitance on the ESC inputs to enable accurate current measurements with a DC meter? Have you checked that with a scope?

Hi awesome video that no load current. Just thinking here if i compare this two motors: www.leopardhobby.com/index.php/En/Goods/detail/id/45 page parameters and this model LBP4092/4D and compare that to this model: www.leopardhobby.com/index.php/En/Goods/detail/id/43 page parameters and this model: LBP4074/2.5Y. Max amps and voltages are near to same, 4074 have little bit bigger amperes because not find exactly same amps. 4092 is must bigger motor physically and have 4200W max power on specs and when you see 4074 specs that are much little motor and have 2600W. I have now this 4074 motor and i think if i change to that must bigger 4092 motor is my output power exactly same like this tinier motor 4074 (about of course bigger motor losses mass and bearings are little bit bigger, but if we ignore that). Do i maybe have better torque all rpm and better "trottle response" with bigger motor and maybe bigger torque? And that max wattage numbers are quite odd. If i have 26v and 110A and 26v and 120A why other motor is 4200W and other 2600W. Or is that something to how much temp and torque/power that motor can physically handle? Sorry if my question is badly writed hope you understand and can help me with this :)

@RCexplained

4 жыл бұрын

Hi Lassi, I'm not sure how I missed your comment. I like to respond to everyone who has a question. Moving to a larger motor with the Kv staying the same, should increase the amount of current that you can run through the motor, thus increasing power. If the load stays the same, theoretically, the overall power output would not change. The specific winds that you have selected do not have similar kv's from what I see. This would suggest you are considering increasing the voltage for the larger motor as the kv is lower. Specifications on that spec sheet do seem like there is something not making sense. I have more recently done a video on motor torque that you'd be able to view.

you forgot to take the controller losses into account.

@RCexplained

4 жыл бұрын

This can be found in great detail within the description of the video.

@russellwilson5246

4 жыл бұрын

@@RCexplained esc insicnifiant...this just dosent sound right to me.

@RCexplained

4 жыл бұрын

Hey Russel, doesn't sound right based on which part?

@russellwilson5246

4 жыл бұрын

@@RCexplained you saying the power losses in the speed controller are insignificant..i dont know maybe your right at full throttle under no load?? maybe the controller does nothing in this situation..but controllers have risistance right...mosfets are mounted on heat sinks...can you do the test and mesure energy used between controller and motor and compare?

@RCexplained

4 жыл бұрын

Resistance in the ESC will cause a voltage drop that can be determined by V=IR. The resistance of a 100 amp rated ESC is very low, typically less than 3 milliohms. Using the formula, the voltage drop across the ESC would be less than 10 millivolts for a larger Io value. (0.1% of the typical voltage Io is measured at) We also know that small variations in voltage don't really effect the Io value at all. Therefore, we are not concerned about these voltage losses. To be able to measure this difference would require very sensitive equipment to measure these very small values of difference. Equipment that I don't have.