What’s a Synchroscope?

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A synchroscope is used to synchronize AC supplies, ensuring they are of the same voltage, frequency, and phase. There are two types: electromechanical and electronic. Electromechanical instruments use opposing windings and a rotor, while electronic synchroscopes use a microprocessor and display. It is important to ensure supplies are balanced before combining them to avoid damage.

A synchroscope is an instrument used to establish phase angle and frequency synchronization between alternating current (AC) supplies. This is a critical safety measure when AC mains or generator outputs are joined or connected together. Synchroscopes are available in two basic formats: electromechanical and electronic. Electromechanical instruments use a series of opposing static windings and a rotor to provide a dial type indication. Electronic synchroscopes use a microprocessor to calculate and indicate the status of the inputs via a digital or light emitting diode (LED) display.

The voltage of an AC power supply consists of a smooth sine waveform that alternates between positive and negative peak values. The peak values ​​are known as the breadth of the supply; the number of times the cycle occurs per second is known as the frequency. When two AC supplies of similar amplitude or voltage are compared, they are considered “in phase” when both reach their peak positive and negative points simultaneously. When mixing AC power supplies, it is of the utmost importance to ensure that both are of the same voltage, frequency and in perfect phase with each other. Connecting AC power supplies when they are not balanced in this way can cause serious damage to your network.

AC power supply voltages are generally quite stable and easy to read with conventional instrumentation. The phase angle and frequency ratio between the supplies, however, is rarely balanced without some adjustment. When generator or mains supplies are combined, a synchroscope indicates any differences between the two. If there is any discrepancy, generator speeds can be adjusted until the synchroscope indicates perfect balance. At that point, supplies can be safely combined.

There are two basic types of synchroscope. The first is of the electromechanical type which indicates the phase and frequency relationships with a pointer and a comparator. This tool is similar in construction to an electric motor. It has a series of 90 degree opposed static stator windings, a polarizing coil and a rotor element which drives the indicator needle. One supply is connected to the stator windings and the other to the bias coil. If the phase and frequency of the two supplies vary, the rotor will spin and give an indication of the difference.

The second type of instrument is the electronic syncroscope. This type uses a microprocessor designed to sample and compare two AC power supplies for phase and frequency characteristics. Any differences between the two are then calculated and indicated on a digital liquid crystal display (LCD) or via LEDs. The latter type of synchroscope typically has a circle of LEDs on the front panel that light up in a predetermined pattern to indicate the presence and magnitude of phase and frequency differences.




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