What is Synchroscope : Circuit Diagram & Its Working

In the concept of alternating current, synchronization is termed as the procedure of equalizing the frequency and the speed of a generator or with the other source for the purpose of operating a network. Without synchronization, the generator does not hold the ability to supply power to the electric grid if not it is functioning at a similar frequency with the network. When the two devices are brought to synchronization, they can exchange AC power. So, synchronization of the generator can be done with the support of a device is called synchroscope. It holds extreme importance that is before paralleling the voltage and frequency of generators are supposed to be synchronized. Thus, the concept of this article is the synchroscope circuit diagram, construction, and other details.

What is Synchroscope?

Synchroscope definition is that it is the instrument that displays the exact instant where the two alternating current generators are in exact phase relation to be in parallel connection. It also shows whether the incoming generator has more operating speed when compared with that of an on-line generator.


Basic Synchroscope Device
Basic Synchroscope Device

Working Principle

The synchroscope working principle can be explained as follows. It has two phases wounded stator and a rotor. The alternators supply a two-phase kind of supply for the device. When there happens to match the phases, then the third phase will get automatically synchronized. The prevailing alternator in the device provides power supply for the stator, whereas incoming alternator provides supply for the rotor.

The phase difference that exists between these two supplies implies the frequency and phase variation of the alternators that are in parallel connection. The device also defines the operating speed (quick or slow) with that of the incoming alternator.

The device will start to function when the alternators of various frequencies have a connection with each other. When both rotor and stator frequency levels are similar, then the rotor will stop to rotate or stays as a constant which means that the dial also stays as static. And when the frequency of the stator and rotor supply varies, then the rotor initiates to rotate which means that the dial starts to deflect.

The rotor speed is based on the variation of the supply frequency level. When the variation is more, then rotor deflects at greater speed and when the variation is minimal then rotor deflects at less speed.


Synchroscope Construction

The below diagram explains the constructional details of the synchroscope and what are the conditions to be followed for the construction of the device.

  • The alternators should possess a similar level of magnitude voltages
  • They should even possess similar frequency levels
  • Also, the same phase series has to be maintained. The operation of this device is to signify any kind of variation that exists either in the frequency or phase levels. The phase series is calculated through a device named as “phase sequence gauge”, and the voltage rating is measured using a voltmeter.

Types of Synchroscope

Synchroscopes are the devices where these are exclusive form for the power factor meters and these instruments are mainly classified as two types and those are of

  • Electrodynamic type
  • Moving iron type

Let us discuss more in detail of each type, the function of synchroscope, and their working.

Electrodynamic Synchroscope

This kind of instrument is even termed as Weston type of Synchroscope where the construction is that includes an electrodynamic device and three limb types of transformer. This forms the static section of the device and the other is a dynamic section.

The one outer limb winding in the static section has a connection with bus bars and the other has a connection with the incoming instruments. And then the central limb that is in the transformer will be connected to the lamp.

Electrodynamo Synchroscope
Electrodynamo Synchroscope

The transformer’s outer limb winding stimulates two flux whereas the central limb flux is the outcome of the flux of the other two limbs. The generated flux stimulates the electromagnetic force in the transformer’s middle winding. And the transformer’s outer limbs are connected in the way that when the incoming alternator has similar phase levels then there will be a maximum amount of EMF generation in the transformer’s middle limb.

This gives a brighter glow for the lamp. In the same way when the incoming alternators are not in phase, then there will be zero amount of flux generation in the transformer’s central limb. This provides no glow to the lamp. In the other case, when the frequency levels of incoming alternators and the bus bars are not in synchronization, then the lamp will be having a flickering movement. The occurrence of flickering is analogous to the variation in frequency levels.

The synchronization in the device can happen when there is enhanced brightness and the flickering amount is minimal. The electrostatic device that is utilized in the system is for the measurement of speed levels of incoming alternators.

The flickering effect in the lamp will not signify the speed of the incoming alternator. In consideration of this, an electrodynamic device is included in the device construction.

It is included with 2 fixed coils and a coil in motion. The two static coils keep minimal current and they are connected to the bus bars through a resistor having resistance ‘R’. The coil that has motion has a connection with the incoming instrument using a capacitor ‘C’. The needle that is in the coil will deflect based on the speed.

When the frequency of the generator is less than that of incoming instrument frequency, then the needle will deflect at maximum speed and vice-versa. The exact synchronization can be known when the pointer stays at the middle position and has slow motion.

Moving Iron Synchroscope

This kind of synchroscope device is included with a static coil in two sections. The static coils are constructed for minimal current and they have connections through the phases of the bus bars. There exists two iron kind of cylinders termed as ‘C1’ and ‘C2’. These cylinders are placed on a shaft and kept apart using spacers.

Every cylinder is supplied with two iron shafts where the axes of the cylinders are separated with 1800. These cylinders energized using the pressure coils P1 and P2 and these have a connection with the incoming alternator phases. One of the pressure coil F is with ‘R’ value of resistance and the other with ‘L’ inductance has a series connection. This creates a phase variation of 900 in between their current values.

The working of this type of synchroscope can be explained as follows:

Moving Iron Type
Moving Iron Type

If the frequency value of the incoming instrument becomes similar to that of the bus bars, then the device functions as the moving iron kind of power factor meter. The deflection of the pointer is analogous to the phase variation that is in between the voltage values. There will be no deflection of the pointer when the phase variation is zero in between the voltages.

In the other condition, when the two frequency values are not similar, then the pointer will deflect at the speed value as per the frequency variation. The direction of pointer deflection decides whether the incoming alternator speed is quick or less. If the pointer deflection is zero, then the synchronization is zero automatically.

This kind of synchroscope is most commonly used for various purposes and they are not expensive and have extended life period too.

So, this article is all about the function of synchroscope, types, construction, and other related concepts. It is more even crucial to know about ?

Image Credits

Electrodynamic & Moving Iron Synchroscope:

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