Question

The amplitude of output voltage signal for certain flow rate in a turbine flow meter was found to be 50 mV. The flux and angular position relationship is given by $\Psi \left(\theta \right)=3+\cos 4\theta mwb$
The rate of rotation of turbine in RPM is ?

• A. 119

Answer 1

The correct option is A 119
$\Psi \left(\theta \right)=3+\cos 4\theta$

$emf\left(e_0\right)=\frac{d\Psi \left(\theta \right)}{dt}$

$=4\omega \cos 4\omega t[\because \theta =\omega t]$

$\therefore \text{Amplitude}|e_o|=\left(4\omega \right)$

$\Rightarrow \omega =\frac{e_o}{4}=\frac{50}{4}$

$\omega =12.5rad/sec$

$now,2\pi rad\to 1revolution$

$\therefore 12.5rad\to 1.989revolution/sec$

$\therefore 12.5rad\to 1.989\times 60revolution/min$

$=119.366\approx 119revolution/min$

$\text{Rate of rotation = 119 RPM}$