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Which of the following is not true for a threephase system compared to 1φ system?
In a balanced threephase star connected system, the phase voltages
Here, linetoline voltage leads the respective phase voltage by 30°.
Three identical resistances are connected in delta against a balanced threephase voltage supply. If one of the resistances be removed, the reduction in the power will be
When all the resistance are present,
(Since V_{ph}= V_{L} for Δ connection)
When one of the phase resistance is removed,
A balanced Yconnected load is supplied from a balanced 3phase 400 V system. If the current in each phase is 15 A and lags the phase voltage by 30°, the total power will be
In a balanced threephase circuit V_{AN}= 1500 ∠20° V and V_{CN} = 1500 ∠100° V.
The value of V_{BN} will be
Since V_{CN} lags V_{AN} by 120°, therefore phase sequence will be ACB.
Here, V_{BN} will lead V_{AN} by 120° but, will have the same magnitude.
so,
The value of the rms line voltage V_{L} for the below circuit if the rms line voltage is 100 V will be
Converting the Δconnected load in star equivalent, we have
So, line to neutral voltage for equivalent Yload
∴ Line current,
∴ Line voltage at source
Two wattmeters, both have reading of 3 kW when connected for the twowattmeter method with current coils in lines A and B of a 600 V ABC circuit having a balanced A load. The Δ phase impedance will be
we have
(Since W_{1} = W_{2} = 3 kW)
or, cosθ= 1
Hence, the load will be purely resistive.
Three capacitances, each of C/3 Farads are connected in delta. Their equivalent star value for each capacitance is
We know that,
The instantaneous value of currents in both phases B and C of a 3phase balanced system are 20 A. For a phase sequence of ABC, the instantaneous value of current in phase A is
Since the system is balanced, therefore
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