Glossary of Terms

[RipTideSports]

Go for it

[Venom121212]

The characteristic that differentiates a RKP from a TKP is the RKP pivot axis and king pin axis are perpendicular to each other where the TKP’s are not.

I’ve needed to read this sentence for so long

[RipTideSports]

I can do a better picture if you like @wandagoner. Really stoked on your thread!

[MoeStooge]

[wandagoner]

the image you posted is good but if there is a better way to showcase the difference between TKP and RKP trucks please post it and we’ll leverage it. thanks again!

[wandagoner]

@Venom121212 Justin, i started the markup formatting clean up however it will be an iterative process as time allows. again great suggestion and i should have started with the appropriate format at the onset

[wandagoner]

added!

[professor_shartsis]

illustration of 50% duty cycle during a single BLDC commutation:

(the actual frequency would be on the order of 20-40 thousand cycles per second)

Noob question thread! ask your questions here!

^you can see half the time (50% duty cycle), 60a current @ 50v is flowing from the battery, averaging to 30a @ 50v

the other half the time, the current flows inductively, and the motor “sees” 60a @ 25v the whole time. but in reality, during the “on times” the current in the motor might be increasing from 59.9a to 60.1a, and during the off times, the current is dropping from 60.1a back to 59.9a, which averages to 60a.

and some explanations for the illustration:

Noob question thread! ask your questions here!

@Krindor increasing the inductance in a circuit means increasing the time it takes for current to increase or decrease with applied or removed voltage.

so for example at 50% duty cycle, the battery could be supplying pulses of 60a, half the time, which averages to 30a. the battery side of the circuit has low inductance and so the current can ramp up to 60a and down to 0a very quickly.

on the motor side, the inductance is very high, so when the current from the battery shuts off, the circuit is rewired/switched so that the leads coming from the motor forms a loop, which allows the current to flow inductively (without applied voltage) for a short time.

the time scale of the on-off pulses from the battery are so short in duration that during the off times when there is no battery current, the current continues to flow in the motor entirely from the inductance.

so 60a from the battery half the time (30a average) can result in 60a in the motor the whole time, because the current still flows in the motor inductively while it is not flowing from the battery, but we say the 60a the motor sees the whole time is half the voltage of the battery if the duty cycle is 50%.

hope this helps.

Noob question thread! ask your questions here!

if you happen to be wondering what “powers” the current that continues to flow in the motor when you remove the battery current… it’s the collapsing magnetic field of the stator which stores energy in the magnetic field itself.

the inductance is directly proportional to the magnetic field produced by a given amount of current, and since the motor produces a large magnetic field for a given current, it has high inductance, and the current still flows for a while when you remove the battery current if you quickly short the motor to itself.

Noob question thread! ask your questions here!

when you send current through the motor, because of the high inductance (created by the coil shape of the winding combined with the iron in the stator, which forms an elecromagnet) it takes extra time to reach a given amount of current, compared to the time it would take if you used a straight wire with no iron stator.

during this “extra time” you are building a magnetic field or “compressing a spring” or “storing energy”… when you remove the battery voltage, the spring releases and powers the current that continues to flow for a short time without any battery voltage.

[professor_shartsis]

illustration of a BLDC electrical revolution at 50% duty cycle (as in ERPM or electrical revolutions per minute)…

*the sequence of phase changes are not necessarily in the correct order, but the possible combinations are:

• red -> green
• red -> blue
• green -> red
• green -> blue
• blue -> red
• blue -> green

^1 electrical revolution cycles through all these combinations, and that happens 7 times per motor rotation assuming 14 magnets

[fessyfoo]

FUB? Funked Up Britisherunits?

Edit:
by which I mean i kinda know what it means but I don’t know what it stands for.
But, I think i finally found it. unless this one is also sarcastic. “Freedom Unit BullS***”

[drone001]

Very informative…I’m still confused about Max brake regen and max brake current. Currently I have my max brake regen set to -24A and Max brake current is set to -54. My brakes are fine the way they are now, I got those settings from a thread but I dont understand them. They appear to do the same thing according to the info in this thread. Can someone please explain…

[wandagoner]

i think this is lazy typing on my part.

Max Brake Current: how much current can be applied for braking force. the lower the value the stronger the braking force. eg -(54) is stronger than -(24).

Max Brake Regen: how much of the braking current is directed back to the battery to charge. couple of schools of thought on this one. some say:

• “high regen current is fine as it’s only for a few seconds”
  or
• “you dont charge your battery at more than (5)amps why regen higher and risk harming the battery”

[drone001]

So -24 is to high for a 12s6p. This number wont change braking strength…correct?

[wandagoner]

@drone001

Currently I have my max brake regen set to -24A and Max brake current is set to -54

I assume you are referring to the -(24)A brake regen in the other post.

@drone001

This number wont change braking strength

Correct Max Brake Regen will not impact your braking strength

@drone001

-24 is to high for a 12s6p

There are differing schools of thought on this number. some say that the battery is fine to accept higher current for short bursts and point to the discharge rate as a supporting metric.

Personally i set my regen to be -(7.5)a per motor on 12s4p P42a cells. this is my personal preference and i have not had issues. your mileage may vary. I appreciate this response is not likely the definitive one you were looking for.

[drone001]

It helps a lot…thx. think I’m going with a lower value. I like to play it extra safe when it comes to batteries.

[BillGordon]

Yes, most go -12 to -15 here.

[drone001]

Yeah I was thinking like -12 myself…thx

[wandagoner]

@linsus
can you please validate the definitions i just added - keep in mind i’m trying to distill down to a pedestrian level of understanding with links for people self educate by diving deeper

@wandagoner

Electromotive Force (emf): Electrical action produced by an energy source, such as a generator or battery measured in Volts. Technically this is the potential difference and can suppy current if connected to a resistance. On the small scale, the potential difference creates an electric field that exerts force on charges, causing current. We thus use the name electromotive force, abbreviated emf.

video description of back emf

https://youtu.be/5mf4NmmLWnE

Back emf: Electromotive Force (emf) generated by a spinning motor. Also called Counter-electromotive force (CEMF).
When something like a refrigerator or an air conditioner (anything with a motor) first turns on in your house, the lights often dim momentarily. To understand this, realize that a spinning motor also acts like a generator. A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor.
At the motor’s operating speed, enough current flows to overcome any losses due to friction and other sources and to provide the necessary energy required for the motor to do work. This is generally much less current than is required to get the motor spinning in the first place.

[linsus]

I’m not so familiar with the abbreviasions in english but I know most of them in Swedish
Most of these are pretty awkward to put into sensible words but looks like you got it down pretty well.
Only thing that you could underline more is that emf directly correlates to the change/variation in the magnetic flux/field(like a sinewave f.e) you can still have a potential in the circuit without variation in the field. If that makes any sense at all

Isnt Back emf technically the same thing? It just specifies the direction?
This case the motor creating the variation in the flux/field -> emf ?