1.0 Introduction
Inverter is known as DC to AC converter. The main work of an inverter is to change a DC input voltage to AC output Ac voltage of desired magnitude and frequency. A variable output v9olateg can be obtained by varying the input voltage and maintaining the gain of the inverter constant. On the other hand, the dc input voltage is fixed and it is not controllable, a variable output voltage can be obtained by varying the gain of the inverter, which is normally accomplished by pulse width modulation (PWM) control within the inverter.
The output voltage wave forms of ideal inverter should be sinusoidal. However, the waveforms of practical inverters are sinusoidal and contain certain harmonics. For low- and medium-power application, square wave or quasi-square-wave voltage may be acceptable, and for high power applications, low distorted sinusoidal waveforms are required. With the availability of high speed power semiconductor devices, the harmonic contents of output voltage can be minimized or reduced significantly by switching techniques.
Inverter can use controllable turn on and turn off devices (e.g. BI Polar junction transistor (BJT), Metaloxide semiconductor Field effect transistor (MOSFETS) etc. or forced commutated thyristors depending on applications. These inverters generally use pulse modulation (PWN) to control signals for producing an ac output voltage. An inverter is called a voltage-fed inverter (VFI) if the input voltage remains constant, a current-fed inverter (CFI) if the input current is maintained constant, and a variable dc linked inverter if the input voltage is controllable.
In Nigeria in particular, the electrical grid is under increasing strain particularly during heavy demand and sometimes insufficient megawatts generated, due to scheduled and unscheduled outages.
1.1 Below Are Some Power Problems That An Inverter Can Solve
- Power failure- Total loss of utility power
- Power sag — short term under voltage
- Power surge (spike)- quick burst of over voltage
- Under voltage — low line voltage for an extended period of time
- Over voltage- increased voltage for an extended period of time
- Line noise — distortions superimposed on the power waveform.
- Switching transient — under-voltage of over voltage for up to a few nano seconds.
- Harmonic distortion — multiple of power frequency superimposed on the power waveform.
1.2 Choosing An Inverter
There are factors to BE considered when choosing an inverter system
1. WATTAGE (W): The wattage rating represents the maximum amount of load that can be plugged into an inverter in different ways. The connected load typically should not exceed 80% of the inverter rating. Special consideration should be made when connecting certain equipment such as printers, photocopies or any type of motorized load.
2. Amount of run time the unit could be able to provide when the power fails. This number varies with the load amount that is plugged into the inverter. For example, a unit may run a single computer for 30 minutes, but with 2 computers plugged in, it might only last for 15 minutes.
1.3 Care For The Inverter
1. Do not overload the inverter
2. The inverter should be kept in a clean and dry place
3. Always handle the inverter with care
4. The sealed load/acid battery has a useful life of 2-5 years. It should be replaced within this period.
This material contains electrical diagrams, circuits, illustrations and more (Very detailed)
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