Brushless Motor Continuous Wattage

[Logan's_Rcs]

Hey all,

So I pulled the logs from my MT410 running a Castle 1520 on 6s, 18 tooth pinion. Maximum wattage came out to 2800 watts during the peak, and usually it rested around 1300 or so. So this leads me to a couple of questions:

1. If 2800 maximum watts from a 1520 gives me the performance I'm looking for (it does, but it gets hot), then would a motor rated for continuous wattage higher, assume 3400 watts run cooler for the same speed?
2. I'm a little confused as to what "continuous wattage" means. Is continuous wattage the power level that a brushless motor can run basically all day long without overheating, or is it something else?

Thank you!

 

[LibertyMKiii]

In theory yes. All these numbers are fuzzy math. In real use scenarios it is always different.
If 5% of the wattage is converted to heat.... you need a larger can to shed the heat. I'd be willing to bet the only way to get that 3400 cont is with a larger diameter and length can. (but you cannot mix castle specs against another brand as they all rate their power differently)

Sometimes you can go pretty far with fans cooling the motor but that is dependent on the ambient temps being reasonable also.

 

[Logan's_Rcs]

In theory yes. All these numbers are fuzzy math. In real use scenarios it is always different.
If 5% of the wattage is converted to heat.... you need a larger can to shed the heat. I'd be willing to bet the only way to get that 3400 cont is with a larger diameter and length can. (but you cannot mix castle specs against another brand as they all rate their power differently)

Sometimes you can go pretty far with fans cooling the motor but that is dependent on the ambient temps being reasonable also.

Ok, so I emailed Castle asking how much continuous wattage the 1520 is able to pull, and they responded saying 1,750 watts. That means that I'm pulling about 1100 watts over continuous, which is explaining why I am getting so much motor heat. A TP 4070 has a continuous wattage of around 3850, so I think I may try going that route and stiffening up the suspension so it doesn't sag with the extra weight of the motor. Hopefully that'll work out ok!

 

[LibertyMKiii]

Ok, so I emailed Castle asking how much continuous wattage the 1520 is able to pull, and they responded saying 1,750 watts. That means that I'm pulling about 1100 watts over continuous, which is explaining why I am getting so much motor heat. A TP 4070 has a continuous wattage of around 3850, so I think I may try going that route and stiffening up the suspension so it doesn't sag with the extra weight of the motor. Hopefully that'll work out ok!

Castle is conservative with their numbers.... but I think this plan will work.

The castle is 40x88 (41mm if you count the fins)
The tp4070 is 40x107mm so you will gain some heat dissipation with the larger can surface area. A fan is always needed, but I think that setup will work well for you.

 

[Logan's_Rcs]

Castle is conservative with their numbers.... but I think this plan will work.

The castle is 40x88 (41mm if you count the fins)
The tp4070 is 40x107mm so you will gain some heat dissipation with the larger can surface area. A fan is always needed, but I think that setup will work well for you.

yeah, I was thinking the same thing. However, even if Castle is more conservative, I was still getting overheating at 2800 watts, so continuous is still very likely below that. At 3800 watts, and subtracting around 400 watts for the losses the motor produces (I calculated this out) I'm still getting 600+ watts over the peak 2800 of my 1520, which equates to almost 1hp, so the power should be good!

 

[LibertyMKiii]

yeah, I was thinking the same thing. However, even if Castle is more conservative, I was still getting overheating at 2800 watts, so continuous is still very likely below that. At 3800 watts, and subtracting around 400 watts for the losses the motor produces (I calculated this out) I'm still getting 600+ watts over the peak 2800 of my 1520, which equates to almost 1hp, so the power should be good!

Worse case scenario you are building up a nice collection of motors

 

[Jerold]

When you see the 2800W how long is that? If it's <100ms I wouldn't even worry about it. The data logs have very poor resolution and the ADC are pretty much junk. Unless you can consistently recreate that I would take it with a grain of salt. If it's a single spike in the log it could have been a glitch picked up buy the ADCs and means nothing.

This is one of my logs, and you can see the current "peaked" at 527A. But you could also say that it spiked at 527A because it's only one data point and the resolution is low (5ms). So, in reality it could be 800A or it could been an actual voltage spike (noise) and it's really like 450A.

As @LibertyMKiii said the numbers are very fuzzy. If you buy an industrial motor they are very specific about what to expect and their products hold too it because they are used where people can get hurt. The RC world has goofed up the spec's six ways from Sunday and the specs are pretty much a marketing joke at this point.

When they say continuous it's more like a rolling average over a longer period of time. The peak shouldn't be sustained for any length of time. Longer time and short period are all very vague and vary depending on who you talk to. If it's spiky it's peak.