Why inverters are used

An inverter provides an ac voltage from dc power sources and is useful in powering electronics and electrical equipment rated at the ac mains voltage. In addition they are widely used in the switched mode power supplies inverting stages. The circuits are classified according the switching technology and switch type, the waveform, the frequency and output waveform.

The basic circuits include an oscillator, control circuit, drive circuit for the power devices, switching devices, and a transformer. The conversion of dc to alternating voltage is achieved by converting energy stored in the dc source such as the battery, or from a rectifier output, into an alternating voltage. This is done using switching devices which are continuously turned on and off, and then stepping up using the transformer. Although there are some configurations which do not use a transformer, these are not widely used.

The DC input voltage is switched on and off by the power devices such as MOSFETs or power transistors and the pulses fed to the primary side of the transformer.

AC Drives can protect motors from damage by accurately controlling the torque. For example, in a machine jam, the motor will continue to rotate until the overload device opens. An AC drive can be set to limit the amount of torque applied to the motor to avoid exceeding the torque limit.

An AC drive can deliver low or high-speed required by the load without speed-increasing or reduction devices and gearboxes.

This saves maintenance costs and floor-space requirements. In procuring AC drives, there are several factors to consider. They are commonly used in conveyor belts, compressors, and pumps. Since LV drives cause less stress to the motor, minimal maintenance is required. It also consumes less energy. An LV drive produces high frequency and better motor performance at low voltage, thus reducing production cost.

On the downside, low voltage creates more current. If LV drives are used with high horsepower HP machines, it generates more heat and increases the room temperature. More current means more generated heat. Installing vents and additional air-conditioning is necessary. Huge and multi-megawatt electric motors in power stations and metal processing plants use MV drives. They require a high input voltage to achieve a high output voltage.

True Sine Wave Inverters have been developed to replicate, if not improve, the quality of power provided by main power grids or power utilities. They are specifically recommended to power high energy-consuming electronic gadgets and equipment. True Sine Wave inverters are more expensive than Modified Sine Wave inverters, and is the more powerful and efficient option of the two.

On the other hand, Modified Sine Wave inverters are much cheaper, and are capable of running a fewer or selected number of household appliances and fixtures, for example - kitchen appliances, lights, and small power tools. However, this type of inverter may not possess the capacity to power high energy-consuming equipment and appliances, for example - computers, microwave ovens, air-conditioners, heaters and laser printers.

The size of inverters range from as low as w, to well over w. If you disconnect an inverter from its DC source, the AC voltage supply is interrupted. However, this naming practice causes confusion, since the purpose of a VFD is controlling motor speed by adjusting voltage and frequency. An uninterruptible power supply or UPS has a self-explanatory name - it provides electric power without interruption, especially during blackouts and power grid disturbances.

However, uninterruptible power is only possible when two conditions are met:. Note that inverters can also be used as backup power supplies, when combined with energy storage systems. However, a conventional inverter cannot achieve the seamless transition offered by a UPS. Inverters can respond in less than one second, but they aren't fast enough to prevent data loss in IT applications. UPS units are much faster, on the other hand, responding in a matter of milliseconds. Assuming the same rated power, a UPS is normally more expensive than an inverter, given its additional components and functions.

UPS units are necessary in applications that demand continuous power during a blackout, but inverters with external batteries are cost-effective when this function is not needed. When you charge batteries using the main electric service, there are two power conversions involved. Battery charging requires DC power, and you need a rectifier when using an AC input. UPS units include this component, but an external charge controller is required if you have batteries connected to an inverter.

Since UPS units are more expensive, it does not make sense to size them for hours of operation with no power supply. Note that energy efficiency measures let you operate longer with backup power.