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Author Topic: Motor Conundrum  (Read 2349 times)

Sandy Calder

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Motor Conundrum
« on: November 09, 2008, 06:51:16 PM »

Quote
CEM 900 High Torque Motor
High Torque 900 motor from Caldercraft Electric Motors (CEM).

Nominal Voltage: 12V
Operating Range: 6-24V
RPM at Nominal Voltage: 3000
No Load Current: 0.4A
Current at Nominal Voltage: 5.0A
Stall Current: 20.3A
Part No: CEM-900T

OK "enlightened ones"!
Please enlighten us about the above.
It made me chuckle but you can actually fill in the blanks when you look at it for a few moments.
I'm looking for answers to power and rpm at maximum efficiency and maximum power.
It appears to be a good motor for direct drive but the vendor tries to make it a puzzle
No prizes.
Regards
Sandy Calder
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RantandRave

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Re: Motor Conundrum
« Reply #1 on: November 09, 2008, 07:59:20 PM »

I can't spot it.......  :((
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Garabaldy

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Re: Motor Conundrum
« Reply #2 on: November 13, 2008, 12:05:13 AM »

all i can see is it only states current drawn at nominal voltage but does not tell us what the current drawn is at maximum efficiency.  it has about the same power output as an MFA 800.  Around 60 watts.  Would this swing a 75mm prop?
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Sandy Calder

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Re: Motor Conundrum
« Reply #3 on: November 13, 2008, 01:14:44 AM »

I got a sheet of A4 covered in figures that I can't understand because I wrote them two days ago.
All I can make out is maximum power 60 watt.
I also have 2030 rpm but I don't if that is at maximum power or efficiency.
I remember it had about 20% more torque than an 800 but was broadly similar.
Possibly at 5 amp the torque is 0.26Nm.Not too sure.

About as much use as the quoted figures but they did add up to a useful direct drive motor.
Regards
Sandy Calder
Wait a minute.I'll just scan and post this tomorrow morning and see if anyone else has any luck.Before anyone does,I think I made a mistake but corrected it.
Hang on.What's this Scottish twenty pound note doing in my scanner?
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roycv

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Re: Motor Conundrum
« Reply #4 on: November 13, 2008, 12:31:44 PM »

Hi all, as a 'rule of thumb' if you take 20 % of the stall current of the motor as your operating current you should hit the maximum efficiency for the motor.  So 5 amps is not far off.
regards Roy
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