You're welcome Flaxbybuck.
I like your work approach, I will follow you with great pleasure and interest.

Hi Chris, good question.

On brushed motors the current passes through both cables (ESC - motor) in a single direction when moving forward and in the opposite direction when moving in reverse, therefore a single fuse is sufficient to open the circuit.

In brushless motors my reasoning is this: If I put just one fuse on just one cable, in the event of an overcurrent it will open the electrical mesh relating to its winding.
No more current will pass through that winding and the motor stops.
Ok, but what prevents electric current from still circulating in the other windings? In my opinion nothing.
I believe (but I could be wrong) that the control circuit of the brushless motor continues to apply voltages at pre-established time intervals (albeit very short) on the other uninterrupted windings (and therefore in electrical continuity).
By continuing to supply voltages on closed electrical meshes, electric current will still circulate.
Therefore, in my opinion, the crux of the matter is not in the switching speed of the three currents but in the failure to open all three circuits.
If I'm making a mistake, please correct me and explain why.

Is there any need to install fuses in all three motor wires for a brushless motor? Given the speed at which power is switched between each, wouldn't one fuse be sufficient?

Only one is used in a brushed motor circuit.

Chris

Thank you all for responding to this subject, and especially to Alessandro - you must have spent quite a time preparing your response.

From the nature of the responses received I form the impression that there is a basic need for definitive advice on this topic that can be readily accessible to all modelers. I'm not sure of the best place for this. Any thoughts ?

Having spent a considerable sum on the battery, ESC and motor I feel it best to install the best protection, so I will insert a fuse between battery and ESC, and three fuses between ESC and motor. Fuse ratings will follow advice given, initially using lower rated fuses. As you say, they are cheap enough.

Again, thank you all for your help 😉

Thanks Alessandro. I'll post my thoughts on one of my build installations so I can work my way through what is required and get my head around the subject better.

Chris

Hi ChrisF, I agree with all your excellent points of view and the considerations you have made.

I dont currently 😊 fit fuses in my builds but may well do so in the future. I've read a number of threads on different forums previously about the subject and as said some do fit fuses and others don't, including very experienced modellers.

In my case the risks are very low as I use good quality ESCs and motors, I don't run my boats hard and our lake is on private land (no rubbish) and the weed is kept well under control, but again as said, why take any risk if for a few £s protection can be easily added?

My only real concern is fire and if I fit a fuse it will be to combat that. I'm glad the wiring has been mentioned as I also think that is the weak link and the fuse should be based on that rather than the motor or other component. The problem for me is sizing the fuse. I use silicone cable from Component Shop and err on the side of safety sizewise but it is the cable fitted by the motor manufacturer that concerns me. If fitted with bullet connecters already and braided as are my Overlander motors it isn't easy to determine the size of the cable but one would hope they are sufficient for the max. current draw of the motor!

I will use car type blade fuses but one thought I do have is that the cable entries use chocolate box type connecters which goes against my use of good quality connectors i.e. XT60 and bullet and is a reason I only want to use the minimum number of fuses.

Hi Flaxybybuck
Sorry if I didn't reply sooner but I had little time and the short pauses were not enough for such a long text.
However, since the first translations didn't seem very comprehensible to me, I shortened many sentences and cut many parts. I hope this is understandable.


Brief answer:


1. Yes.

2. 40A.

3. Yes. Three fuses, one on each cable.

4. 20 Ampere (based on the data you provided).



Complex and reasoned answer (can be ignored and not read by those who consider it useless).

I am absolutely certain about the need to protect the circuit (cables, connectors, motors, ESC, battery), even if many "experts" disagree.
On the positions of the fuses I am quite sure of what I say (very inclined to change my mind if there are concrete elements).
I have no absolute certainties about the amperage thresholds and I am still in the study/learning phase.

During the period in which I participated in the forum I heard interesting advice regarding the correct size of fuses such as that of ColinH. Below I put the relevant links.

Well, I liked both Len1 and Roy, although there are differences between their opinions, not only because I like them and always make very useful interventions but because I agree with their statements, later you will understand why.

First I'll tell you how I did it. From here we can continue with other reasoning.
I used a single 20 Amp fuse, positioned between the brushed motor and the ESC.
At his time, I analyzed the motor's plate data, considered the sections of the cables and carried out practical tests in the tank with an ammeter in series, to measure the electric currents (test in water).
I realize however that I am very conservative (cautious).

I start from the fact that if a person has correctly sized his "electrical system" (from the battery to the engine) he can still risk seeing his ship go up in smoke, even though he has done everything right.
Electrical surges are not a rare occurrence when we are dealing with an electric motor.

Position between ESC and electric motor.
As already mentioned several times (every naval modeller knows this), vegetation, ropes or other material can get caught between the propeller blades and brake or completely block the propeller.
In these cases we will have much higher currents than the operating ones.
This is the most common case to take into consideration.
To overcome this accidental event, simply place a fuse between the ESC and the motor.
For brushed motors, only one is enough because the current flowing on one cable is the same as the current flowing on the other cable.
In your case you need three different fuses (one on each cable) because there are three different currents circulating alternately on the three cables, connected to the respective windings.
The brushless direct current motor normally powers the stator windings to create the rotating magnetic field, which (due to the effect of combined attractions and repulsions) will rotate the permanent magnets.

Size of fuses between ESC and electric motor.
As regards the size of the fuses between the motor and ESC, it is necessary to look at the operating electric current and the maximum current of the electric motor to safeguard the motor, it is necessary to look at the current carrying capacity of the electric cables to safeguard the cables, it is necessary to look at the carrying capacity of the connectors to safeguard the connectors.
I know that many modelers recommend considering the maximum current that the motor can absorb and choosing a fuse with lower amps (For example 5 Amperes less, as ColinH suggested to me). Some say 20% less.
So far I have instead considered the normal nominal operating current of the motor and used a fuse with higher amperes (between double and triple), always taking into account the electric current absorption tests in the tank.
In short, I used a very empirical (very conservative) method.
The first is probably the most correct.
In your case the max load current is 50 A, so 45 or 40 Amp fuses should be fine. However I believe that 45 amp currents can damage your motor in the long run.
In fact, I have found that the best datasheets are those that also indicate the time that a certain electrical device can support certain currents. The operating current is the one that does not create problems even for very long periods of time.
On the other hand, you cannot choose a size that is too small for the fuse, because at start-up the currents are always higher (short-lived peaks).
This is why I don't put instantaneous fuses.
Yours is a fairly expensive motor that needs to be safeguarded.
In any case 40 Amperes would be too many for 16 AWG cables. I agree with Len on this.
You wrote that the capacity is 22 amps (I found even lower values) therefore a 40 amp fuse is suitable for the motor but not for the cables.
However, anyone can ask themselves: Why does the manufacturer put such small cables? Good question. In my opinion precisely because they are sized for the operating current and not for the maximum one.
But I too am waiting for other opinions.
Your engine datasheet is too sparse to make more in-depth considerations.

Fuse between battery and ESC.
The three fuses between the ESC and the electric motor are of no use if there is a short circuit upstream.
For example, if a short circuit occurs between the contacts of the ESC itself, the three downstream fuses (between motor and ESC) will not trip because there will be no electric current passing through them.
It's very difficult for a short to happen there but not impossible. For this reason, even if I didn't put it, I say that it is right to put it for greater safety.
Now the question is: But an upstream fuse (between ESC and battery) protects everything downstream, so what need is there to also put fuses between ESC and motor?
Good question. I'm not sure if my answer is right but I say this:
I'm not sure that the current intensities flowing between the ESC and the motor and between the ESC and the battery are the same.
While waiting for further information and tests which I will carry out when I have time, I believe it is better to protect the two circuits separately.
In any case, if the only fuse upstream of everything (between ESC and battery) is to protect all components, it should actually have a lower cut to also protect the three 16 AWG motor cables.

It is also true that many interruptions are not healthy for the circuit.
In this I agree with Roy.
I prioritize the safety of equipment and cables and use a contact cleaning spray on mobile junctions.

If you install a 20 Amp fuse, first test it in the bathtub at maximum power for a few minutes. If the (car) fuse breaks (but I don't think so) use a larger one (25 A, 30 A).

Here are other very interesting interventions and opinions:

forum/130156

forum/130229

please keep in mind that the size of the fuse should not only protect the motor or what every it is trying to protect but must also be sized so that it protects the wiring. No sense putting a 50A fuse to protect the motor if the wiring is only 22ga, just an outlandish example. Len

Hi Flaxbybuck.
Basically Roy wrote, in my opinion, all the correct things.
I'm writing my personal opinion, but the translator betrays me. Sorry, I need some time.