What is a Generator?

A generator is a device that transforms mechanical or chemical energy into electrical energy to provide portable power to operations or to prevent discontinuity of activities during a power outage. In particular, a diesel generator is the combination of a diesel engine with an electric generator to generate electrical energy. A generating set (genset) comes in various sizes, packaged to meet different needs, set sizes range from 8 to 50 kVA single phase or three phase for use in homes, shops, and office, with the larger industrial generators, up to 2500kVA are used. At Kubota, we provide a wide range of gensets to meet your business needs.

How does a generator work?

The modern day generator works on the principal of electromagnetic induction that the flow of electric charges could be induced by moving an electrical conductor, such as a wire that contains electric charges, in a magnetic field. This movement creates a voltage between the two ends of the wire or electrical conductor, which in turn causes the electric charges to flow thus generating electric current.

A generator is made up of 9 main components, each with a different function.

1. Engine: Is the source of the input mechanical energy to the generator. The size of the engine is directly proportional to the maximum power output the generator can supply. There are several factors that you need to keep in mind while assessing the engine of your generator. The manufacturer of the engine operation specifications and maintenance schedules.

• Type of Fuel Used – Generator engines operate on a variety of fuels such as diesel, gasoline, propane (in liquefied or gaseous form), or natural gas. Smaller engines usually operate on gasoline while larger engines run on diesel, liquid propane, propane gas or natural gas. Certain engines can also operate on a dual feed of both diesel and gas in a bi-fuel operation mode.
• Overhead Valve (OHV) Engines versus non-OHV Engines – OHV engines differ from other engines in that the intake and exhaust valves of the engine are located in the head of the engine’s cylinder as opposed to being mounted on the engine block. OHV

2. Alternator: is known as the “Genhead”, making up part of the generator that produces the electrical output from the mechanical input supplied by the engine. It contains an assembly of stationary and moving parts encased in a housing. The components work together to cause relative movement between the magnetic and electric fields, which in turn generates electricity.

• Stator – Stationary component which contains a set of electrical conductors wound in coils over an iron ore.
• Rotor / Armature – Moving component that produces a rotating magnetic field through 1) Induction, 2) Permanent magnets, 3) Using an exciter.
• The rotor generates a moving magnetic field around the stator, which induces a voltage difference between the windings of that stator. This produces the alternating current (AC) output of the generator.The following are factors that you need to keep in mind while assessing the alternator of a generator:

Metal versus Plastic Housing – An all-metal design ensures durability of the alternator. Plastic housings get deformed with time and cause the moving parts of the alternator to be exposed. This increases wear and tear and is hazardous to the user.

Ball Bearings vs Needle Bearings – Ball bearings are preferred and last longer.

Brushless Design – An alternator that does not use brushes requires less maintenance and also produces cleaner power.

3. Fuel System – Fuel tank usually has sufficient capacity to keep the generator operational for 6 – 8 hours on an average. In the case of small generator units, the fuel tank is a part of the generator’s skid base. For commercial applications, it may be necessary to erect and install an external fuel tank. Common features of the fuel system includes: 

• Pipe connection from fuel tank to engine – the supply line directs fuel from the tank to the engine and the return line directs fuel from the engine to the tank.
• Ventilation pipe for fuel tank – the fuel tank has a ventilation pipe to prevent the build up of pressure or vacuum during the refilling drainage of the tank.
• Overflow connection from fuel tank to the drain pipe – This is required so that any overflow during refilling of the tank so does cause spillage of the liquid to the generator set
• Fuel pump – This transfers fuel from the main storage tank to the day tank. The fuel pump is typically electrically operated.
• Fuel water separator / fuel Filter – Separates water and foreign matter from the liquid fuel to protect other components of the generator from corrosion and contamination.
• Fuel injector – This atomizes the liquid fuel and sprays the required amount of fuel into the combustion chamber of the engine.

4. Voltage Regulator – Regulates the output voltage of the generator. The mechanism is described as each component regulates the output voltage of the generator. The mechanism is described below against each component that plays a part in the cyclical process of voltage regulation.

• Voltage regulator: converts AC voltage to DC current.
• Exciter windings: converts DC current to AC current.
• Rotating rectifiers: converts AC current to DC current.
• Rotor / Armature: converts DC current to AC voltage.

This cycle continues till the generator begins to produce output voltage equivalent to its full operating capacity. As the output of the generator increases, the voltage regulator produces less DC current. Once the generator reaches full operating capacity, the voltage regulator attains a state of equilibrium and produces just enough DC current to maintain the generator’s output at full operating level. 

5. Cooling and Exhaust Systems – continuous usage of the generator causes its various components to get heated up. It is essential to have a cooling and ventilation system to withdraw heat produced.

• Fresh water is sometimes used as a coolant for generators, but these are mostly limited to specific situations like small generators in city applications. Hydrogen can be used as a coolant for the stator windings of large generator units since it is more efficient at absorbing heat than other coolants. For common applications, both residential and industrial, a standard radiator and fan is mounted on the generator and works as the primary cooling system.
• It is essential to check the coolant levels of the generator on a daily basis. The cooling system and raw water pump should be flushed after every 600hours and the heat exchanger should be cleaned after every 2,400 hours of generator operation. The generator should be placed in an open and ventilated area that has adequate supply of fresh air.
• Exhaust system – exhaust fumes emitted by a generator are just like an exhaust from any other diesel or gasoline engine and contain highly toxic chemicals that need to be properly managed. Hence, it is essential to install an adequate exhaust system to dispose of the exhaust gases.

6. Lubrication System – Since the generator comprises moving parts in its engine, it requires lubrication to ensure durability and smooth operations for a long period of time. The generator’s engine is lubricated by oil stored in a pump. You should check the level of lubricating oil every 8 hours of generator operation. You should also check for any leakages of lubricant and change the lubricating oil every 500 hours of generator operation.  

7. Battery Charger – The start function of a generator is battery-operated. The battery charger keeps the generator battery charged by supplying it with a precise ‘float’ voltage. If the float voltage is very low, the battery will remain undercharged. If the float voltage is very high, it will shorten the life of the battery. Battery chargers are usually made of stainless steel to prevent corrosion. They are also fully automatic and do not require any adjustments to be made or any settings to be changed. The DC output voltage of the battery charger is set at 2.33 volts per cell, which is the precise float voltage for lead acid batteries. The battery charger has an isolated DC voltage output that does not interfere with the normal functioning of the generator. 

8. Control Panel – The user interface of the generator and contains provisions for electrical outlets and controls. Different manufacturers have varied features to offer in the control panels of their units. Some of the main features are:

• Electric start and shut-down. Auto start control panels automatically start you generator during a power outage, monitor the generator while in operation and automatically shut down the unit when no longer required.
• Engine gauges – different gauges indicate important parameters such as oil pressure, temperature of coolant, battery voltage, engine rotation speed and duration of operation, constant measurement and monitoring of these parameters enables built-in shut down of the generator when any of these cross their respective threshold levels.
• Generator gauges – control panel also has meters for the measurement of output current and voltage, and operating frequency.
• Other controls – phase selector switch, frequency switch and engine control switch (manual mode, auto mode) among others.

9. Main Assembly / Frame – All generators, portable or stationary have customized housings that provide a structural base support. The frame also allows for the generator to be earthed for safety.