Jan 24, 2013, 01:11 PM Registered Crasher United States, TX, Coppell Joined Feb 2011 2,226 Posts Again, they're talking continuous, not pulses. If they were all on all the time, the motor wouldn't turn at all. At any given time, 1 phase is +v, 1 is -v, and the other is 0v. See here: http://www.rcgroups.com/forums/showp...postcount=2661 The first pic is WOT, and you'll notice that that phase is still switching on and off constantly. And clearly from other scopings, the real number exceeds the numbers that are used for the ratings (which are the same as you get with a wattmeter). If you look here, you can see all 3 phases at once: http://www.rcgroups.com/forums/showthread.php?t=1166779 You'll notice that worst case scenario is where 2 phases are "on" and the 3rd is "off". (The graphs look inverted, but that's normal. Up is off, down is on). This pretty much establishes a good definition of a 2/3 duty cycle, if you ask me. If you average 3 parts with one being zero, then you get: continuous input amps(wattmeter) = 2*(pulse amps) / 3 The pulses have to be higher than the average if only 2 out of 3 of them are on at any given time. Taking CC at their word is not enough for me. If they can show measurements or theory to back what they say, it's just more heresay in my eyes.
Jan 24, 2013, 01:17 PM
Parkzone junkie
United States, MI, Grand Traverse
Joined Oct 2008
3,771 Posts
Quote:
 Originally Posted by dav3uk A pulse cant be a straight line, its not a pulse. If you had straight line input to all 3 phases the motor would stop.........or am I missing something here Dave
I think he meant the draw would look like a straight line, as in the exact instant phase 1 shuts off phase 2 opens and the exact instant P2 is off P3 goes full. This would mean 100% on at all times and the current would be a straight line.

-Brian
 Jan 24, 2013, 01:21 PM Registered User Joined Mar 2011 212 Posts [Removed by User Last edited by Retiredtech; May 29, 2013 at 01:19 AM.
 Jan 24, 2013, 01:32 PM Registered User USA, TX, Arlington Joined Aug 2010 290 Posts From what I understand about the brushless controllers, they are basically 3 phase DC switches with 2 phases conducting at any given moment. The third non-conducting phase is measured for zero crossing of back EMF for timing reference of the next pulse. So the FET's do see full battery voltage and current on their conducting phase. A 12 pole motor (which the parkzone BL15 is) will need each phase conducting 6 times per revolution, and yes, all portions of the circuit will have to be able to sustain the full voltage and current whether it be low throttle or full throttle in short. Like was said before, the current measuring device will only represent an average reading that it sees and not the full current/voltage that is actually introduced to the ESC/Motor.
Jan 24, 2013, 01:37 PM
Registered Crasher
United States, TX, Coppell
Joined Feb 2011
2,226 Posts
Quote:
 Originally Posted by Retiredtech What? Let me ask this question. Who should one believe; one of the most trusted ESC companies that engineers, builds, tests, and sells these switched ESCs; or someone blowing smoke on a user thread? Are you trolling?? RT
I'll believe the measurements, which is what I keep posting. It's pretty clear that the FAQ is massively simplified so they don't confuse customers. I'm not saying nobody there knows it, I'm just saying what you are posting on the FAQ is just somebody's opinion with no supporting evidence given.
Jan 24, 2013, 01:41 PM
Registered Crasher
United States, TX, Coppell
Joined Feb 2011
2,226 Posts
Quote:
 Originally Posted by kalmon I think he meant the draw would look like a straight line, as in the exact instant phase 1 shuts off phase 2 opens and the exact instant P2 is off P3 goes full. This would mean 100% on at all times and the current would be a straight line. -Brian
But that's averaged over time, which is not what we're talking about here. We're talking about the pulse peak current, which as I said before, is quite a bit higher than that.

CC is saying each phase is averaging the full current, and this is true. They aren't saying anything at all about the actual peak currents seen on each phase. It's also true that each phase has a 2/3 duty cycle, on average (it's on 2/3 of the time), so there is equivalence there that CC is talking about. However, the non-averaged current is at least 1/3 more than the average.
Jan 24, 2013, 01:42 PM
Parkzone junkie
United States, MI, Grand Traverse
Joined Oct 2008
3,771 Posts
Quote:
 Originally Posted by jtaylor996 This pretty much establishes a good definition of a 2/3 duty cycle, if you ask me. If you average 3 parts with one being zero, then you get: continuous input amps(wattmeter) = 2*(pulse amps) / 3 The pulses have to be higher than the average if only 2 out of 3 of them are on at any given time. Taking CC at their word is not enough for me. If they can show measurements or theory to back what they say, it's just more heresay in my eyes.

summary:
Full throttle: watt meter shows7.45V and 1.3A, oscilloscope showed: 2.3Amps
"Half" throttle: Watt meter shows: 7.5V and 0.95A, oscilloscope shows: 3.2 amp peaks!

That's real life independent measurements that back up Castles claims.

-Brian
 Jan 24, 2013, 01:46 PM Registered Crasher United States, TX, Coppell Joined Feb 2011 2,226 Posts Actually, CC is claiming that it should read 1.3A at all times.
Jan 24, 2013, 01:51 PM
Registered Crasher
United States, TX, Coppell
Joined Feb 2011
2,226 Posts
This just about sums up things (directly in response to Bruce's pics above):
http://www.rcgroups.com/forums/showp...2&postcount=61

Quote:
Jan 24, 2013, 02:04 PM
Parkzone junkie
United States, MI, Grand Traverse
Joined Oct 2008
3,771 Posts
Quote:
 Originally Posted by jtaylor996 Actually, CC is claiming that it should read 1.3A at all times.
I understand the this is very oversimplified as your other quote from "vintage1" clearly shows, however:
Castle claim that the motor will see 50% more at full then at half...
2.3A actual from oscilloscope +50% is
2.3 * 50% = 1.15 + 2.3 = 3.45amps ..... I'd say that 3.2 is pretty darn close to 50% more.

I think the original intent of this has been lost though, I was merely trying to show why not to use that beautiful 4 bladed prop and throttle management. I think that has been thoroughly explained....maybe a little to thoroughly.....

I would love to continue the discussion as I always love to learn more about the way things work. Feel free to PM me or even start a ESC thread and link me to it. I just don't want to derail the P-47 thread any more.

-Brian
 Jan 24, 2013, 02:07 PM Registered Crasher United States, TX, Coppell Joined Feb 2011 2,226 Posts Ok, to summarize this conversation so far (which I think is necessary at this point): There are at least 2 kinds of ratings and failures for ESCs: 1. Hi current (peak) burn out. Happens instantly from way too much current going through a single pulse. 2. Hi temp burnout. Happens over time from heat dissipation. The ratings the manufacturers give are in regards to #2, and (should be) based on destructive testing. These numbers are at least 30% lower than what is actually seen in #1. If you use a severely undersized ESC, you'll run into #1, as it's just not designed for that current and will short (I'm guessing burn out the FETs). If you moderately undersize your ESC, then it'll just get too hot and you'll run into #2. You're reading #2 with your watt meter. If you turn the throttle down, it goes down and looks OK. However, it's still not OK to use an ESC undersized and just keep the throttle down, because you'll run into problem #1. If it weren't for #1, this would probably work fine, as you're keeping the heat off the ESC and motor (newton's laws of thermodynamics right there), but that has nothing to do with problem #1 because it's not a heat thing.
Jan 24, 2013, 02:40 PM
Registered User
United States, OR, Irrigon
Joined Sep 2011
174 Posts
Quote:
 Originally Posted by jtaylor996 44A static on the stock motor may be ok. In the air, that's only 40A, which is a common enough rating for a lot of similar sized motors. The pain in the butt is not knowing what it can actually handle since there are no specs. I've been having a lot of success lately with exceed rocket 3020 motors in 3d planes. The 950kv version is rated for 44A. I also use an 860kv version to swing a larger prop. The cool part is that they are only ~\$20! I'm getting 550W+ out of them on 3s. Just food for thought in case your BL15 does go out.
I'm using 3 of the 3025s', J. So far they are doing fine and I do like the pricetag. In fact I am running one in my PZ P-47.
 Jan 24, 2013, 02:49 PM Registered User United States, OR, Irrigon Joined Sep 2011 174 Posts Fun and educational discussion, Guys. I agree totally with the esc needing to be sized up. We people need to be sure and learn something new everyday and increase our understanding about how things work.
 Jan 24, 2013, 03:22 PM Registered User Joined Mar 2011 653 Posts Anyone have a Parkzone P-47 box and packing foam they want to give me/sell me? I just got orders to Japan and am trying to figure out how to get this guy safely packed and shipped! Wonder if parkzone would sell me just the box?
Jan 24, 2013, 03:28 PM
Newbe learning everyday!
United States, OH, Parma Heights
Joined Aug 2012
889 Posts
Quote:
 Originally Posted by Barrett_G Anyone have a Parkzone P-47 box and packing foam they want to give me/sell me? I just got orders to Japan and am trying to figure out how to get this guy safely packed and shipped! Wonder if parkzone would sell me just the box?
There is a guy on eBay that sells parkzone stuff I bought a box for my extra t-28 from him.just search a parkzone micro and you will see one of his planes. He always writes eBay across the front of the box so he should be pretty easy to find.im sorry I don't remember his name. But if you call them they are real easy to deal with.