The synchronous reactance per phase of the 460 V, 60 Hz, Y-connected 6-pole synchronous generator is 1.2 Ω. Full load armature current 30 A (at 0.8 reverse power-coefficient). Rotary losses 1.5 kW and core losses 1.0 kW (60 Hz, full load). The armature resistance winding losses are neglected. The excitation current is adjusted so that the terminal voltage is 480 V when the generator is running unloaded. According to this: a. What is the rotation speed of the generator? b. What will be the terminal voltages of the generator in the following cases? 1. At rated load and current and a reverse power-coefficient of 0.8; 2. At rated load and current and a power-coefficient of 1.0; 3. At rated load and current and a forward power-coefficient of 0.8; c. What is the efficiency of the generator when operating at rated current and a reverse power-coefficient of 0.8?
Synchronous Generator
In comparison to an asynchronous generator, it is a machine where the rotor speed is equal to the rotating magnetic field produced by the stator, i.e., mechanical speed is equal to the electrical speed, thus called synchronous, and not asynchronous.
Salient Pole Rotor
Salient pole rotor includes a large number of exposed poles mounted on a magnetic wheel. The construction of a bright pole is as shown in the image on the left. The proposed poles are made of metal laminations. The rotor winding is provided on these poles and is supported by pole shoes.
The synchronous reactance per phase of the 460 V, 60 Hz, Y-connected 6-pole synchronous generator is 1.2 Ω. Full load armature current 30 A (at 0.8 reverse power-coefficient). Rotary losses 1.5 kW and core losses 1.0 kW (60 Hz, full load). The armature resistance winding losses are neglected. The excitation current is adjusted so that the terminal voltage is 480 V when the generator is running unloaded. According to this:
a. What is the rotation speed of the generator?
b. What will be the terminal voltages of the generator in the following cases?
1. At rated load and current and a reverse power-coefficient of 0.8;
2. At rated load and current and a power-coefficient of 1.0;
3. At rated load and current and a forward power-coefficient of 0.8;
c. What is the efficiency of the generator when operating at rated current and a reverse power-coefficient of 0.8?
D. How much shaft torque should be applied by the drive machine when the generator is running at full load?
to. What happens to the induced torque?
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