Generator Synchronization: What It Is, How To Do It, And The Benefits Of Using It.


We'll talk about generator synchronization in this essay, including its principles and benefits.

Maintaining the smooth operation of your equipment is made simple by generator synchronization. It's a fantastic method to reduce your energy costs as well.

You might also like to read How to identify whether a diesel engine generator's turbo is terrible.

What Is Generator Synchronization?

Generators are used in diesel engines to produce electricity and run the machine. Generator synchronization is a process where two or more generators are connected so that one will start when the other stops. It allows them to run at the same speed and produce power at the same rate.

Generator synchronization could also mean matching the timing of a generator’s output to that of an engine’s output.

You can synchronize the generator's output with the engine's input by controlling the speed of both devices. When synchronized, they will produce power at the same rate so that one device does not have more power than the other. You can achieve synchronization through various methods, such as adjusting either engine or generator speeds.

Because it needs to be operated at synchronous speed to generate AC power with the desired frequency, it is called a synchronous generator.

How do generators synchronize?

The generator synchronization of diesel engine work, in general, is the process of matching the phase angle, voltage magnitude, phase sequence, and frequency of the generator to a second generator.

Phase angle

The busbar and generator alternator's phase angle ought to be zero.

You can check whether these characteristics are the same between your busbar and generator alternators using the generator synchronization technique.

Voltage magnitude

If the alternators and bus bars are not parallel, voltage magnitude can result in serious interruptions. A high reactive power level in your grid could be dangerous if the alternator voltage is greater than the busbar. The generator may malfunction if the alternator voltage is too low since it will have to absorb a lot of reactive power from the busbar.

Phase Sequence:

The phases of your electric grid or bus bar must be in the same order as the three phases of the alternators in your system.


When frequencies are out of balance, energy flows become unstable. This instability could result in generator damage. Find out What is the difference between kVA and kW in generators?

Synchronization techniques for generators

There are two ways to synchronize the generators. These include emergency synchronizing lamps, three bulb method, and the Synchroscope method.

1. Emergency synchronizing lamps or three-bulb method.

When the synchroscope fails, this technique is applied. The emergency lamp method is employed because there should be a backup mechanism to synchronize the alternator in case of failure.

Between the three busbar phases and the incoming generator, three lamps need to be connected.

The lamps are only connected in this way because if they were united in series when the incoming machine is out of phase with the switchboard, all the lights in the same stage would turn on and off simultaneously.

1. In this method, when the incoming machine comes into phase with the bus bar, two lamps will be bright, and one light will be dark.

2. The movement of these bright and dark lamps indicates the speed of the incoming machine.

3. As an illustration, there will be times when lamp A is dark and lamps B and C are bright. Similarly, there will be times when lamp B is dark, and the others are bright, and there will be times when lamp C is unclear and the other two are bright. In this instance, the movement of the lighting from dark to bright creates a clockwise direction, indicating that the machine is operating quickly.

4. The speed of the incoming generator varies in a clockwise and an anticlockwise direction.

These LEDs' ON/OFF frequency is determined by the bus bar frequency and alternator-2 voltage. Reduce the flickering rate if you wish to match the frequency. The diesel engine speed controller manages the alternator's speed.

The lamps will go dark after these circumstances are met, and you can then close the synchronizing button to synchronize alternator 2 with alternator 1.

This method's primary flaw is that it can only distinguish between the bus bar and the alternator-2 by measuring the flashing rate. However, this method does not reveal the alternator frequency of the bus bar frequency.

1. Two Bright and One Dark Lamp Method.

The alternator frequency can be compared to the bus bar frequency using this method to determine whether it is greater or lower.

1. When you connect the light L2 across the pole on the centerline of the synchronization switch, much like the dark lamp approach, except the lights L1 and L3 are connected in the reverse order.

2. The voltage condition testing is similar to the previous method, and after that, the lamps will all glow brightly and inky black. Whether the alternator frequency is lower or higher than the bus bar frequency depends on the sequence in which the lights turn on and off.

3. The order in which L1-L2-L3 turns light and dark suggests that the entering generator frequency is higher than the bus bar frequency. You must reduce the alternator speed until the flickering rate is minimal and diesel engine speed control is applied.

4. Conversely, the flashing L1-L3-L2 sequence shows that the bus bar frequency is lower than the incoming alternator frequency.

5. To limit the flickering rate as much as possible, the prime mover speeds up the alternator. The synchronization switch is closed when lamps L1 and L3 are equally bright, and lamp L2 is dark.

The drawback to this approach is that you cannot confirm the authenticity of the phase sequence. On the other hand, for permanently linked alternators, where the phase sequence is sufficient for the first time of operation, this condition is excessive.

3. Use of the synchronometer

A synchroscope is used to measure the frequency difference between the voltages originating from the generators and the grids.

The synchroscope is made up of two poles on a tiny motor that has coils connected across two phases. Let's assume that the armature windings are coupled to the red and yellow degrees of the arrival machine and fed by the red and yellow phases of the switchboard busbars.

1. The bus bar circuit has parallel connections for both inductance and resistance.

2. The current in the inductor circuit is 90 degrees delayed compared to the wind in the resistance.

3. With the use of slip rings, these two currents are supplied into the synchroscope and directed toward the armature windings, which create a spinning magnetic field.

4. With variations in the red and yellow phases of the incoming machine, the polarity of the poles will alternately change in the north/south direction.

5. The rotor will rotate either clockwise or anticlockwise in response to the spinning field's reaction with the poles.

6. When the rotor is rotating in a clockwise direction, this indicates that the incoming machine is going more quickly than the bus bar and more slowly when it is traveling counterclockwise.

7. The pointer on the synchroscope will rotate clockwise if you significantly increase the alternator speed, which is often desirable.

8. Just before the pointer hits the noon position, when the arriving machine is in phase with the bus bar, the breaker is shut off. It is because one starts the process a little bit earlier. After all, it takes the contractor a few extra milliseconds to pull in.

9. As the synchroscope gets closer to noon, the "slip" between the sine waves approaches zero at noon, and the voltage difference between the phases is also at its lowest point. We achieve a closure time close to noon by shutting off the breaker at 11 o'clock.

Advantages and disadvantages of the Synchroscope technique

1. It is more precise than lighting, for one.

2. The operator's subjective perception of the precise moment of synchronization is all but gone.

3. It is more expensive than lighting.

4. It does not specify the phase order.

Why do we need Generator Synchronization?

When a single available generator capacity cannot carry the required load, synchronization is needed,o or more alternators cooperate to power the bag, and synchronization becomes necessary. The two or more generators generating the power must be connected and run parallel to manage more oversized loads because electrical loads are not constant.

Parallel operation refers to using multiple tiny units instead of a single generator. Parallelization requires synchronization, and many commercial plants favor this configuration since it:


If one component requires maintenance, the other systems can continue to function, preventing the shutdown of your entire business.


Generators perform most efficiently when you load them to their maximum capacity. Your system can adjust to load variations so that it always operates efficiently.


Your load needs could change during the day. To accommodate larger and lower loads with more or fewer active systems, modify your parallel system.


More extensive operations call for greater power. Systems with more generators have more alternators, which increases their capacity.

More Trustworthy.

With many alternators, parallel operation is far more dependable than single-unit generators. In a single-unit system, the entire apparatus will shut down if the alternator fails. In a similar design, the other alternators keep the system going even if one fails.

You should avoid damaging the device and the power system, and it would be beneficial to be cautious when synchronizing a generator to a power system. When synchronizing a generator to a power grid, the frequency and voltage must coincide.

It is necessary to close the rotor angle and quick power system phase tip before turning off the generator breaker and connecting the isolated generator to a power system.

An automatic synchronizer with manual control capabilities is needed to automate the synchronization procedure for generators.

Synchronizing panels frequently indicate any governor and excitement changes the operator must make and when it is safe to turn off the breaker.

The thermostat is also necessary for "hot" countries, as you can see.

Citations: Generator arrangement -; Marine Electrical Equipment and Practice by H.D. Mcgeorge.


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