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Aug 10, 2017, 06:30 PM
Registered User
Thread OP
Question

Motor/ ESC troubleshooting


I have a Super Tigre 400 and Super Tigre 20 amp ESC in a Hobbico Nextstar Mini. This is not the original motor/ESC but this was the stock set up. When I connect the battery, the motor/ESC arm without issue. The issue is I can fly for about 3-4 minutes and the motor quits abruptly. After a few minutes it will start up again and fly for a few minutes before shutting down again. I conducted a test on the ground and it did shut down after about 3 minutes running at about 40-50% throttle. During the test I checked the motor and ESC to see it either or both were getting hot. When it shut down the ESC was warm but not hot. The motor was much hotter. I think the thermal shutdown on the ESC is 230F.
I guess my question is based on this info is it safe to say the motor is the problem and not the ESC? is there any way to determine which component is faulty?

Thanks
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Aug 10, 2017, 11:52 PM
Sokol
JureZ's Avatar
do you have the means to measure the actual current from the battery into the esc?
more data on the motor, like Kv, or better a link perhaps?
what propeller are you using?


is it this motor perchance ?

http://www3.towerhobbies.com/cgi-bin/wti0001p?I=LXXGY2

SPECIFICATIONS

Diameter: 1.1" (28mm)
Length: 1.18" (30mm)
RPM/V (kV Rating): 950
Weight: 1.8oz (50g)
Input Voltage: 7.4-11.1V
Max. Constant Current: 13A
Max Surge Current: 18A
Max Constant Watts: 145W
No Load Current: .6A
Suggested Prop Sizes: 9x3.5SF - 11x7SF
Connectors: 3.5mm Male Bullet
Aug 11, 2017, 08:55 AM
Registered User
Thread OP
Yes, that is the motor. I am using the stock 9x6 slow fly prop. I do not have a way to measure the actual current from the battery to ESC. I know the ESC low voltage cutout is set at .67 the battry voltage when the battery is connected. Are you possibly suggesting the ESC is not recognizing the correct voltage and setting the low voltage cutout at a higher value? I charge the batteries on a balance charger, Electricfly Triton 2 EQ, and the voltage is indicated at 12.6 when the charge cycle is complete. I'm using 11.1v 1300 mah 10 c and 20 c batteries.
Aug 11, 2017, 08:59 AM
Registered User
Thread OP
How and where do you measure the actual voltage to the ESC? I have a simple test meter but I am beginning to realize if I stay in electrics I will have to invest in a good digital multi meter.
Aug 11, 2017, 09:42 AM
Sokol
JureZ's Avatar
according to the specs listed above, you are over loading the motor with a 9x6 propeller.

the prop suggestions are

input Voltage: 7.4 V => 11x7SF
input Voltage: 11.1 V => 9x3.5SF


I would use at 3S an 8x4.7 as an alternative propeller choice.

Harbor Freight sells a very cheap voltmeter you may use, but not for current measurement.
A current clamp meter would be a good option.

Also, you could buy a watt meter for about $25 , often they appear in the for sale section , or a new one.

I have one of these
http://media.hyperion.hk/dn/em2/

for sale here:
http://www.allerc.com/advanced_searc...1bd493&x=0&y=0
Last edited by JureZ; Aug 11, 2017 at 09:47 AM.
Aug 11, 2017, 09:59 AM
Sokol
JureZ's Avatar
Quote:
Originally Posted by david1958
... I'm using 11.1v 1300 mah 10 c and 20 c batteries.
note that the 3S 1300 mah 10 c battery is good to 13A max (on a good day )

the 20C battery would be good for 26A max.
Aug 11, 2017, 01:53 PM
Registered User
Thread OP
That's interesting that motor specs indicate the prop is oversize, since that's the stock prop. I have flown this set up numerous times before until this issue started recently. I must admit, I have had numerous "learning experiences" and motor/wiring had taken a beating. Is it possible some of the wiring has broken down causing the motor to overload?
I have a 8x6 electric prop, but is is not listed as a slow flyer. Do you think it will work? Is there a difference between a electric sand slow flyer electric?
Also, why can you use a larger prop on lower voltage ? Seems backwards. As you can tell I am new and trying to learn.
Aug 11, 2017, 02:08 PM
Registered User
david1958
Any electric motor has a maximum design current it can withstand.
The voltage applied controls the speed the speed of the motor.
The size/pitch of the prop determines how much current the motor will draw
So less volts reduces the motor speed which in turn reduces the current the motor will draw
A bigger prop can be used to bring the current draw back up to the motor's design limit.
But remember power is the product of Volts times Amps so even though the motor can be drawing it maximum rated current at a lower voltage it will be producing less power.
Aug 11, 2017, 02:25 PM
Registered User
Thread OP
Thanks. That seems to make sense. Since the motor will turn slower at lower voltage the larger prop will move more air or create more thrust, at a slower speed, but too large a prop can still overload.
Aug 11, 2017, 02:25 PM
Sokol
JureZ's Avatar
Quote:
Originally Posted by david1958
..
Also, why can you use a larger prop on lower voltage ? Seems backwards. As you can tell I am new and trying to learn.
with lower voltage, the shaft will be turning at a slower rate and therefore will require less power , if you keep the same prop.

my thinking is that you have battery problems, not good for the load you demand.

The propeller is also overloading the motor , which as you say , is getting very hot.
Aug 11, 2017, 07:28 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by david1958
... The motor was much hotter....
... is there any way to determine which component is faulty?...
Magnets may also have been overheated, see items 5 and 6 below

Several simple motor tests
  1. Opening an outrunner for visual inspection
  2. Drytesting brushless motors - WFF (RCG user vollrathd)
  3. Generator test I, only using a power drill and a voltmeter
    (Re)winding and building motors - RCG (sticky) → opening post → #40 Generator test
  4. Generator test II, not accurate, using a second brushless motor and powerdrill
    Three Phase Alternator - Three Phase Motor? - RCG
  5. Overheated magnets result in lower magnet strength (irreversible! ), which in turn results in higher Kv. Motorcurrent is proportional to Kv cubed
    Higher current → hotter motor → weaker magnets → higher Kv → higher current → hotter motor → weaker magnets → higher Kv → higher current ⟲⟲⟲ etcetera etcetera, temperature runaway
  6. Determining whether magnets still have original strength, by determining whether Kv motor parameter (in rpm/volt) is still the same, several simple straightforward methods.
    www.bavaria-direct.co.za → motor constants

Quote:
Originally Posted by david1958
... I am beginning to realize if I stay in electrics I will have to invest in a good digital multi meter.
close out: Hyperion watt-meter II (optical tach, servo tester, local&remote logging)

Quote:
Originally Posted by JureZ
... A current clamp meter would be a good option. ...
Make sure it's a DC clamp meter.

There's a lot of other wattmeter discussions.

Prettig weekend Ron
Last edited by Ron van Sommeren; Aug 11, 2017 at 07:44 PM.


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