ESC Components selection for special application

[Serge]

Hi,

I am new to RC with limited knowledge. I have a background engineering knowledge in the industrial side.
RC is very different and special.

I have searched and read a lot right and left but cannot find clear answers to my questions.
I need help to select and match batteries with ESC and motor.

I am looking for a high voltage (relative to RC) and high power kit with a brusless motor.
I need 55000 rpm (higher is better) and around 4000 W of peak power (15 sec max).
Continous is not important but should be about 2000 W.
I would like to operate at 51.8 V (14S) with my speed at nominal voltage.
Efficiency is also important, but less than power.

How do you choose the optimal kv of the motor?
I found that RPM = kV (V-IpRm), is this simple equation valid with a 3 phase AC motor of this kind?
Do you keep a margin?

What is the voltage drop of typical ESCs? (mosfets do have a voltage loss)

When the peak power of the motor is not provided, how do you estimate it from the nominal rating?

The max rpm is rarely provided (strange!!). Can I exeed the (kv X max volt) for short bursts?
Can I exceed the max voltage?

If I cannot find the ideal kv, can I use a higher than necessary kv and operate at less than 100% pwm?
Can I set a maximum current in the ESC to protect the motor?
Can I set the maximum speed in the ESC to protect the motor?

In my application, the batteries/ESC/motor will never be disconnected.
Is it possible to shut off the ESC? If yes, how fast could it be powered back on?

Do you have suggestions for motors I could use? (I know Neumotors, but to expensive).

Thanks for your help.

Serge

 

[fran11784]

Hi,

I am new to RC with limited knowledge. I have a background engineering knowledge in the industrial side.
RC is very different and special.

I have searched and read a lot right and left but cannot find clear answers to my questions.
I need help to select and match batteries with ESC and motor.

I am looking for a high voltage (relative to RC) and high power kit with a brusless motor.
I need 55000 rpm (higher is better) and around 4000 W of peak power (15 sec max).
Continous is not important but should be about 2000 W.
I would like to operate at 51.8 V (14S) with my speed at nominal voltage.
Efficiency is also important, but less than power.

How do you choose the optimal kv of the motor?
I found that RPM = kV (V-IpRm), is this simple equation valid with a 3 phase AC motor of this kind?
Do you keep a margin?

What is the voltage drop of typical ESCs? (mosfets do have a voltage loss)

When the peak power of the motor is not provided, how do you estimate it from the nominal rating?

The max rpm is rarely provided (strange!!). Can I exeed the (kv X max volt) for short bursts?
Can I exceed the max voltage?

If I cannot find the ideal kv, can I use a higher than necessary kv and operate at less than 100% pwm?
Can I set a maximum current in the ESC to protect the motor?
Can I set the maximum speed in the ESC to protect the motor?

In my application, the batteries/ESC/motor will never be disconnected.
Is it possible to shut off the ESC? If yes, how fast could it be powered back on?

Do you have suggestions for motors I could use? (I know Neumotors, but to expensive).

Thanks for your help.

Serge

Hi Serge, may I ask what your building? Knowing that will help the most

 

[Serge]

Hi Serge, may I ask what your building? Knowing that will help the most

Hi,

Thank you for your reply.

My questions are for general understanding and may actually apply to any RC project as well.
Don't stick too much to my numbers.
This one would be a kind of portable high air speed blower. I cannot tell you more here.
I could also build a kart and the same questions apply even if at lower speed. (High peaks for accelerations)

I have several applications in mind and I am interested in RC but found the information so far confusing and/or incomplete.

If I missed a source of all this information, Please just give me a link and I will look at it.
My main questioning is the bettery/ESC/motor interaction and voltage matching.

Regards

Serge

 

[RandyDSok]

You are asking a bit outside of my own experience... but some of the questions are the same for smaller motors as larger ones so.... I will likely mention stuff you will know or may be obvious once you read it. I'll only touch on what I can.... for any other info, perhaps someone else may help.

kV is the same on any motor type... even if they are of different types like the AC vs the motors used in RC craft. The majority of the brushless motors are also 3 phase, they are just using a different method than the AC motor.

A higher kV motor can also run at lower speeds... they are limited by their max but can slow down from that also.

I dont' believe the ESC controls the minumum/maximum settings... the controller that is operating the ESC does that, at least in RC components. Another method to limit a motor would be with the addition of a governor.

The ESC's we use in RC don't have an off switch. To turn them off, we disconnect the battery so you'd need to provide another method ( like a high amp switch ) to do what you were asking.

Being able to exceed the specs ( voltage, wattage and/or amperage ) of a any device will depend on it's build quality. Cheaper components typically are not going to live long if you exceed their specs where a well built quality device may be able to. In any situation, it's the heat the device can stand that will probably determine how much you can exceed those specs. If you can also provide additional cooling, you can push the specs even further. The down side to that, is it also will typically shorten their lifespan considerably if you exceed them too much or too often. With electronics, I like the analog of something that is going to, at some point, go over a cliff... each time you push it closer, it can't be pushed back... eventually it will fall off of the cliff.

Consider making the batteries removable. Rechargeable batteries do have a limited lifespan. In addition, being able to switch to an additional battery will allow you to let the first one rest and time to recharge.

Battery amperage output is related to both their capacity ( typically in RC rated in MAH ) and their C rating. 1000mah = 1ah. A 1000mah battery rated at 1C is capable of providing 1a of power at it's max. A 1000mah rated at 2C has twice the amperage output of the 1C battery... so it can provide up to 2a of output.... and so on. Using that... a 5000mah 1C battery can provide 5a and a 2C can provide 10a etc.

 

[Serge]

You are asking a bit outside of my own experience... but some of the questions are the same for smaller motors as larger ones so.... I will likely mention stuff you will know or may be obvious once you read it. I'll only touch on what I can.... for any other info, perhaps someone else may help.

kV is the same on any motor type... even if they are of different types like the AC vs the motors used in RC craft. The majority of the brushless motors are also 3 phase, they are just using a different method than the AC motor.

A higher kV motor can also run at lower speeds... they are limited by their max but can slow down from that also.

I dont' believe the ESC controls the minumum/maximum settings... the controller that is operating the ESC does that, at least in RC components. Another method to limit a motor would be with the addition of a governor.

The ESC's we use in RC don't have an off switch. To turn them off, we disconnect the battery so you'd need to provide another method ( like a high amp switch ) to do what you were asking.

Being able to exceed the specs ( voltage, wattage and/or amperage ) of a any device will depend on it's build quality. Cheaper components typically are not going to live long if you exceed their specs where a well built quality device may be able to. In any situation, it's the heat the device can stand that will probably determine how much you can exceed those specs. If you can also provide additional cooling, you can push the specs even further. The down side to that, is it also will typically shorten their lifespan considerably if you exceed them too much or too often. With electronics, I like the analog of something that is going to, at some point, go over a cliff... each time you push it closer, it can't be pushed back... eventually it will fall off of the cliff.

Consider making the batteries removable. Rechargeable batteries do have a limited lifespan. In addition, being able to switch to an additional battery will allow you to let the first one rest and time to recharge.

Battery amperage output is related to both their capacity ( typically in RC rated in MAH ) and their C rating. 1000mah = 1ah. A 1000mah battery rated at 1C is capable of providing 1a of power at it's max. A 1000mah rated at 2C has twice the amperage output of the 1C battery... so it can provide up to 2a of output.... and so on. Using that... a 5000mah 1C battery can provide 5a and a 2C can provide 10a etc.

 

[Serge]

"The ESC's we use in RC don't have an off switch"
This is kind of weird in my mind.
A industrial motor and drive is never disconnected.

OK but what happend when you are in line waiting to lift a plane with battery connected?
Does the ESC draw power from the battery and how much?
Does the propeller rotate?

How does the ESC react if you cut the throttle signal completely?

 

[RandyDSok]

The battery connector doubles as the "switch" .... Actual switches add weight and are costly when talking about the amperage loads we often see.

The throttle on the transmitter is set to all of the way down, so the motor isn't spinning. In addition, some transmitters also have throttle hold switches to provide some additional safety in case we accidentally move our throttles.

If the receiver looses signal completely like if a transmitter is turned off or other situation... they will default to the safe mode settings they have set beforehand.

I would have answered the "how much power the ESC draws" before had I known.... I just know there is always some loss from heat so none of them are 100% efficient... their efficiencies are typically not listed and really don't concern us as much in the hobby.