Synchronous Machines

This guide covers three phase generator construction, voltage regulation, its rating, cooling methods, excitation control and several solved examples. The three-phase generator has two main windings: 1. A three-phase AC winding 2. Another winding carrying DC. In most cases the rotor has the DC winding and the stator the AC …

An iron core onto which the coils are wound improves the voltage output by increasing the flux density, but causes two undesirable effects: eddy-current losses and hysteresis losses. Eddy-Current Losses Since iron is an electrical conductor, the rotation of an iron core within a magnetic field generates an EMF in …

Referring to electromagnets, if a coil is connected to a DC source a magnetic field is generated in the coil. Consider now if the source is AC with a frequency of 50 Hz. Again, a magnetic field is generated, but this time its north and South Pole swap places rapidly …

A synchronous generator is a machine that produces AC voltage when its shaft is rotated. A synchronous generator is called synchronous because the generated voltage waveform it produces is synchronized with the rotation of the generator. Synchronous Generator Basics A synchronous generator is an ac generator in which the output …

There are two basic types of 3-phase generators (alternating-current generators): (1) the revolving-armature type (Figure 1) and (2) the revolving-field type (Figure 2).  The 3-phase revolving-armature generator rotates the three single-phase windings, located 120 mechanical degrees apart on the rotor assembly, around the inside of a fixed or stationary electromagnetic …

The losses in a synchronous machine affect its cost, rating, and performance. The efficiency of a synchronous machine is frequently determined by measuring the losses, using techniques that are precisely defined by ANSI, IEEE, and NEMA measurement standards. The efficiency is defined in the same way as it is for …

The equivalent circuit for one phase of a synchronous motor is shown in Figure 1. It is similar to the synchronous generator equivalent circuit, but with two differences. First, it has been flipped to show the power system as the input to the motor, and, second, the current is referenced …

The synchronous motor is identical in construction to the synchronous generator, although virtually all synchronous motors are of the salient-pole type. Like all electric motors, the synchronous motor converts electrical power into mechanical power. The primary difference in operation, however, is that the synchronous motor only delivers torque and power …

When bringing a synchronous generator online, we are faced with the necessity of paralleling it with the rest of the power system. Figure 1 illustrates the problem. Conditions for Synchronizing the Generator with the Grid (Power System) Once the generator is operating, we would like to close the switch to …

Most of the electricity we use on a daily basis is created by synchronous generators. Synchronous generators produce constant-frequency power and can operate at both leading and lagging power factors. Delivered power for the round-rotor machine From figure 1, we can write a voltage equation: $\begin{matrix}   {{E}_{a}}={{V}_{t}}+jI{{X}_{s}} & {} & …

In the Synchronous Machine section, we have seen that there are two rotating magnetic fields in the airgap of the synchronous machine whether it is operating as a motor or as a generator. Any time a magnetic field passes by a conductor, it will induce a voltage in the conductor. Thus, …

In this section, we will describe the operation of the synchronous generator. Figure 1 shows a cross-section of a round-rotor synchronous generator, and Figure 2 shows a cross-section of a salient-pole synchronous generator. Both are two-pole synchronous generators. The primary difference between the two types is evident from looking at …

The synchronous motor, like all other rotating motors, has a stator and a rotor. Figure 1 shows a cutaway view of a synchronous motor. The rotor contains electromagnets, which create the field of the motor. In some cases, permanent magnets are used on the rotor of a synchronous machine to …

Stepper motors are close relatives of brushless DC motors. The brushless DC motor is used where continuous motion is required, such as a fan or a disk drive. The stepper motor, on the other hand, is designed to move infinite increments (steps) in either direction and to keep track of …

Regardless of which type of electric machine is chosen for a particular job, efficiency is important for several reasons. First, and perhaps most obvious, a less efficient machine will cost more to operate. Second, the losses in the machine are converted to heat, which raises the operating temperature of the …