Question

A 208-V, 45-kVA, 0.5-pf-leading, delta-connected, 60−Hz synchronous

machine has a synchronous reactance of 2.5Ω and a negligible armature resistance.
Its friction and windage losses are 1.5 kW, and its core losses are 1.0 kW.
Initially, the shaft is supplying a 15 -hp load, and the motor's power factor is 0.85 leading.
The field current If at these conditions is 4.0 A.
Assume that the flux in the motor varies linearly with the field current.
Write a computer program to plot Ia versus If (V-curve) for the synchronous motor with
a 10 -hp load and a 20-hp load.

Answer 1

The question involves creating a computer program to plot the armature current (Ia) vs. field current (If) V-curve for a synchronous motor at different loads, taking into account variables such as power factor, losses, and the flux-field current relationship.

Step-by-step explanation:

The subject question pertains to the characteristics of a synchronous motor under varying operational conditions. It primarily focuses on plotting the armature current (Ia) as a function of the field current (If) for different load scenarios, which is typically represented by a V-curve in synchronous machines.

To achieve accurate results in the plot of Ia versus If, one needs to consider the motor's power factor, losses, and the linear variation of flux with respect to the field current. The student is tasked with creating a computer program to generate these graphs for 10-horsepower (hp) and 20-hp loads, assuming 0.85 leading power factor for the former and unspecified for the latter.

Furthermore, to perform a comprehensible comparison, it's important to understand the principles of back emf, the motor's resistance, and how these factors interact under different loads and operational speeds, as exemplified by direct current (DC) motor cases provided in the reference information.