Motor–generator facts for kids

A motor-generator is a special machine that changes one type of electrical power into another. Think of it like a translator for electricity! These machines are used to change things like the frequency (how fast the electricity wiggles), the voltage (how strong the electricity is), or the phase (a way electricity is delivered).

Motor-generators can also act like a shield, protecting sensitive electrical equipment from problems in the main power supply. In the past, big motor-generators helped convert huge amounts of power for factories. Smaller ones were used to turn battery power into higher voltages for different devices.

Today, most motor-generators have been replaced by smaller, more modern electronic parts called semiconductor devices. For example, rectifiers are used to change alternating current (AC) into direct current (DC), and inverters do the opposite, changing DC into AC.

What is a Motor-Generator Set?

A motor-generator set is usually made of two main parts connected together. One part is an electric motor, and the other part is an electric generator. The motor takes in electrical power and uses it to spin the generator. The generator then produces new electrical power with the desired changes.

How Do Motor-Generators Work?

Imagine you have electricity that's not quite right for what you need. A motor-generator set can fix that!

• Changing Voltage: Sometimes you need to make electricity stronger or weaker. A motor-generator can take in power at one voltage and output it at a different, more suitable voltage.
• Changing Frequency: In some places, the electricity "wiggles" at 50 times per second (50 Hz), and in others, it's 60 times per second (60 Hz). A motor-generator can change this frequency if needed.
• Changing Phase: Electricity can come in different "phases," like single-phase or three-phase. A motor-generator can convert between these different types of power delivery.
• Electrical Isolation: This is like putting a barrier between your sensitive equipment and the main power grid. If there's a sudden surge or dip in the main power, the motor-generator can help protect your devices from damage.

Why Were They Used?

Before modern electronics, motor-generators were super important for many industries. They were reliable and could handle a lot of power. For example, they helped power large factories, railway systems, and even early radio transmitters.

The Rise of Semiconductors

Over time, new technologies came along. Semiconductor devices, like those found in your computer or phone, are much smaller, more efficient, and often cheaper to make.

• Rectifiers: These are electronic devices that can change AC power (like the power from wall outlets) into DC power (like what batteries use).
• Inverters: These devices do the opposite, changing DC power into AC power. This is useful for things like solar panels, which produce DC, but homes need AC.

Because semiconductors are so good at these tasks, motor-generators are not as common today for many applications. However, they are still used in some special situations where their unique features are needed, like for very high power applications or when extreme electrical isolation is required.

Images for kids

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  Aircraft radio modulator unit from the Second World War, showing a dynamotor (the black cylinder) which converts the aircraft's 24–28 V DC to 500 V DC for the transmitter. Dübendorf Museum of Military Aviation

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  An MG set used to provide a variable three phase AC voltage for an Electron Beam Welding Machine high voltage power supply.