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A device for converting direct current into alternating current; it may be electromechanical, as in a vibrator or synchronous inverter, or electronic, as in a thyratron inverter circuit. Also known as dc-to-ac converter; dc-to-ac inverter.


Device for converting direct current (DC) electricity into the alternating current (AC) form required for most home uses; necessary if home-generated electricity is to be fed into the electric grid through net-metering arrangements.



(1) In electric current conversion technology, a device used for the conversion (inversion) of current or voltage. A distinction is made between dependent inverters (those driven by an electric power system) and autonomous inverters.

In dependent inverters a control valve V, a resistance R, and an inductance coil L are connected between the DC and AC supplies (see Figure 1). When operating in the rectifier mode (early firing of the valve) the phase shift ϕ between the voltage of the DC machine and the fundamental wave of current passing through the valve is less than 90°. The AC machine operates as a generator; the DC machine, as a motor (Figure l, a). In the inverter mode (late firing of the valve) the phase shift ϕ is greater than 90°; the AC machine operates as a motor, and the DC machine operates as a generator. For a transition from the rectifier mode to the inverter mode it is also necessary to change

Figure 1. Diagram of current conversion: (a) rectifying mode, (b) and (c) inversion mode; (V) valve, (U) voltage, (R) ohmic resistance, (L) inductance coil, (Em) voltage amplitude, (w) circular frequency, (t) time

either the polarity on the direct current side (Figure l,b) or the direction of current through the valve (Figure l,c). To restore the control of the valve, there must be a negative potential for some time after the passage of a current pulse. Therefore, the phase shift in the inverter mode usually is not equal to 180° and the reactive power (at fundamental frequency), called the shift power, also circulates in the AC circuit.

In autonomous inverters (Figure 2) a capacitor C is charged through choke D by a DC supply. The capacitor is then discharged through the valve V and the primary winding of the transformer T. A pure alternating current is obtained in the secondary winding of the transformer.

Figure 2. Diagram of self-exciting (autonomous) inverter

(2) In computer technology, an inverter is an electron device with one input and one output. An output signal is generated only in the absence of an input signal. Such a device is used to produce the logic operation “NOT.” A distinction is made between potential and pulse inverters.

Potential inverters provide a low output voltage level at high input voltage level, and vice versa (Figure 3). Pulse inverters invert the pulse signal. There are two possible types of pulse inverter: inverters that change the polarity of the input signals (Figure 4,a) and inverters that generate an output signal in the absence of an input signal and do not generate a signal in the presence of a pulse in the input circuit. In this case the polarity relationship between the input signal and the output signal is meaningless (Figure 4,b).

Figure 3. Diagram of a potential inverter: (a) with a triode tube, (b) with a p-n-p transistor; (A) input signal, (P) output signal, (R) ohmic resistance, (C) capacitor, (E) DC (or direct voltage) power supply

Figure 4. Diagram of a pulse inverter: (a) with a pulse transformer, (b) with ferrite cores;(A) input signal, (P) output signal, (C) clock pulses, (Ub) bias voltage

Operational amplifiers in analog computer systems are also called inverters. They are used in achieving transformations of the type

Xout(t) = − Xin(t)


An electrical component that converts direct current into alternating current.


(1) A logic gate that converts the input to the opposite state for output. If the input is true, the output is false, and vice versa. An inverter performs the Boolean logic NOT operation.

(2) A circuit that converts DC current into AC current. Contrast with rectifier.