Electromechanics Laboratory
Electrical Engineering 208
Experiment 7
Synchronous Machine Line Synchronization
Cooperative Engineering Program
Springfield, MO
Laboratory Work
Introduction
Begin by connecting the Lab Volt console to the variable DC power source. Then turn on the
console and connect it to the laboratory computer.
Lab Volt DC Machine
The Lab Volt DC machine will be studied in more detail in a later experiment. In this
experiment the DC machine is simply used as a prime mover to drive the Lab Volt Synchronous
machine. The magnetic field for the DC machine may be supplied from a separate DC source or
may be supplied by windings in the machine itself. The first case is referred to as separatelyexcited and the second case if referred to as self-excited. A self-excited DC machine may be
excited by a series coil, a shunt coil, or both. The latter is referred to as compound excitation.
Lab Volt Synchronous Machine
The Lab Volt synchronous machine has three AC windings in the stator, which may be
connected in delta, or wye. The machine has also has a field winding which is connected to a
DC source.
Lab Volt Synchronizing Lights
The Lab Volt synchronizing lights are used to insure that the voltage, phase sequence, and
frequency of the synchronous machine in the lab are the same as those in the electrical network
on the grid. Make sure that the line-to-line voltage on the synchronous machine in the lab is the
same as that of the grid. Verify that the phase sequence is the same by making sure that all the
synchronizing lights light simultaneously. If this is not the case, then reverse two of the leads on
the machine. Finally adjust the speed of the synchronous machine until it is very close to that of
the line frequency. At that point you may close the switch.
Laboratory
As directed in the Missouri S&T laboratory handout, connect the variable DC supply to the
terminals of the DC machine and also connect the shunt field winding to the DC source. Use the
rubber belt to connect the DC machine to the Synchronous machine. Connect the three phase
windings of the Synchronous in wye and connect the rotor DC field of the synchronous machine
to the DC supply.
Note how the speed of the synchronous machine can be varied when it is not synchronous with
the line but after the machine is synchronized with the line the speed is fixed.