Test: Inverters - 1 - Electrical Engineering (EE)

In low-power electronic circuits oscillators are used for converting dc power into ac power. These oscillator use transistors for converting dc voltage into sinusoidal ac voltage. Since transistor is used in active region, therefore there is substantial loss of power which decreases efficiency. In high power applications inverters are used instead of transistors and the inverters operate in saturation region or cut-off region. Thus, assertion is true but reason is false.

• In CSI at light load, commutation time is considerably increased, which can restrict the highest frequency. Hence, commutation is load dependent process in CSI. Thus, statement-1 is correct.
• A VSl requires an additional line commutated converter for reverse power flow while it is hot so for a CSI i.e. a CSI has inherent four quadrant operation. Thus, statement-2 is correct.
• In VSl, dynamic braking is applicable during ac line failure. Thus, statement-3 is correct.
• MOSFET and transistor are more suitable for VSl not for CSI because in CSI large transient voltage is produced during commutation. Hence, statement-4 is not correct.

Output is a square wave with an amplitude of 100V.
RMS value of a square wave is equal to its peak value.
So, rms value of output voltage is

A voltage source inverter is one in which the d.c. source has small or negligible impedance. Due to low internal impedance, the terminal voltage of a VSI remains substantially constant with variations in load. Reason is also a correct -statement because due to low time constant of internal impedance any short-circuit across the terminals of a VSI causes current to rise very fast. Hence, both assertion and reason are true but reason is not the correct explanation of assertion.

The n^th harmonic-component of output voltage is

The lowest harmonic is third harmonic

The fundamental output voltage for a modulation index of M is

A CSl can be either load commutated or force commutated.