- Motor Generator Set Definition: A motor generator (M-G) set is defined as a device that includes a motor and a generator connected through a common shaft to convert electrical power from one form to another.
- Applications: M-G sets convert voltage, phase, and frequency of power and isolate electrical loads from the supply line.
- Working Principle: The motor in the M-G set receives electrical energy, rotates its shaft, which is coupled to the generator, thereby converting mechanical energy back into electrical energy.
- Power Conversions: M-G sets can convert AC to DC, DC to AC, DC at one voltage level to another, different frequencies of alternating power, and single-phase AC voltage to three-phase AC voltage.
- Modern Alternatives: Semiconductor devices such as thyristors and MOSFETs now often replace M-G sets due to their smaller size, reduced losses, and easier control.
A motor generator (M-G) set is defined as a device consisting of a motor and a generator mechanically coupled through a common shaft. It’s used to convert electrical power from one form to another, such as converting voltage, phase, or frequency.
Motor generator sets also convert voltage, phase, and frequency of power. They help isolate electrical loads from the supply line. Here is a picture of an M-G set.
Here a motor and a generator are coupled together using a single shaft; they are wound around a single rotor. Necessary condition for coupling is that rated speed of both motor and generator should be same.
The diagram of a motor generator set is shown below,
Working Principle of Motor Generator Set
In a typical motor generator set, power is supplied to the motor, which rotates its shaft. This rotation, being mechanically coupled to the generator’s shaft, makes the generator convert this mechanical energy back into electrical energy.
Thus while the power at the input as well as output side is electrical in nature, the power flowing between the machines is in the form of mechanical torque. This provides isolation of the electrical system as well as some buffering of power between the two electrical systems.
Conversions
The motor generator set can be used for conversions of electrical power in various forms
- AC to DC – This is possible by using an AC motor (induction motor or synchronous motor) and a DC generator.
- DC to AC – This can be accomplished by using a DC motor and an AC generator.
- DC at some voltage level to DC at another voltage level.
- Alternating power at one frequency to Alternating power at another frequency
- Fixed AC voltage to variable or regulated AC voltage
- Single phase AC voltage to 3 phase AC voltage
Nowadays, motor generator sets have been upgraded in many ways. They were used where precise speed regulation was needed, like in elevators and factories. Today, semiconductor devices such as thyristor, SCRs, GTOs, and MOSFET often replace M-G sets because they are compact, have lower losses, and are easier to control.
