have a rms value of an alternative current

[Yohann]

I realized an application that permit the characterisation of an electrical motor.At the beginning of the test, the rotation speed of the motor is constant then I increase the torque on the motor and I record the current, the speed and the torque applied on the motor with my application developped with Labview 6.1. But I have a problem with the current (it's an alternative current), I'd like to have rms value of this current to calculate the efficiency of the motor. For this moment, it's not possible because the evolution of the current compared to the torque is not linear.

[wiebe@CARYA]

Hi,

Is it correct that you aqcuire the motor current and speed, and want to
calculate torque from the current, and the power from the torque and speed
(that is probably the only way..).

If you want to convert the current to the torque, you'll have to now how to
do this. The manufacturer might have some numbers (a,b and c for a
polynome), otherwise, you'll need to calibrate using a motor with a known
torque...

Once you have the torque it's simple. P [W] = t [Nm] * speed [RPS (or Hz)]

The calibration might be hard.

Good lock,

Wiebe.

"Yohann" wrote in message
news:5065000000080000008D7B0000-1042324653000@exchange.ni.com...
> I realized an application that permit the characterisation of an
> electrical motor.At the beginning of the test, the rot
ation speed of
> the motor is constant then I increase the torque on the motor and I
> record the current, the speed and the torque applied on the motor with
> my application developped with Labview 6.1. But I have a problem with
> the current (it's an alternative current), I'd like to have rms value
> of this current to calculate the efficiency of the motor. For this
> moment, it's not possible because the evolution of the current
> compared to the torque is not linear.