Electric Motor specifications

[ErAmirKhan]

Hello Everyone,

I am working on a project where I will be using electric motor aa driver.....but the motor output torque is low and for that I will be attaching planetary gearbox to multiply torque... Now the problem is I'm unsure about the motor output torque... I'm using one angle grinder motor and the specifications are attached in the file below...there are 2 powers input and rated and one torque is mentioned in the specifications If I cross check the speed using following formula
P=2πNT/60
The speed I'm getting is not matching with the speeds mentioned in the specifications... I have checked it with 1600 watts and 14Nm torque and 2400 watts and 14 Nm torque, And the speed I'm getting is 1090 rpm and 1637 rpm for 1600 and 2400 power respectively.

Pls help what I'm doing wrong as I'm new to electric motors

 

[waross]

Use;
Speed at rated load 5800 rpm
Torque 14 Nm / 124 in-lbs

2400 W minus 1600 W equals 800 W heat loss.
But beware.
The torque figure given may be peak or stall torque, not torque at rated load.

 

[ErAmirKhan]

Hey Waross,
Thanks for the quick response.
If I calculate power considering 5800 rpm and 14 Nm torque, it is coming 8500 watts.. which is not matching with the power mentioned in the specifications.
Thanks

 

[waross]

I have seen specs for similar motors on circular saws that were misleading.
They torque may be te maximum torquw.
But, a universal motor develops maximum torque at locked rotor or zero RPM.
Unfortunately, any torque at zero RPM equals zero HP making calculations meaningless.
I suggest using 1600 Watts and speed at full load, eg; 5800 RPM to calculate allowable torque.
Note that the motor will develop more torque than your calculations but that if a load demands more continuous torque the motor will overheat.
And, continuously demanding 110% of allowable torque will develop 121% additional internal heat.

 

[ErAmirKhan]

Thanks Waross for the help. Now I think im clear about the torque. I'll just check the actual torque with some torque testing bench.

 

[jraef]

I call these sort of numbers "Marketing values"... used to mislead consumers about "More power!", when in fact they are referring to values that cannot be sustained for more than a few seconds.