Govt. Exams
Entrance Exams
Modern digital multimeters have very high input impedance (typically 10 MΩ for voltage measurement) to minimize loading effects on the circuit.
The accuracy class (e.g., 1.5, 2.0) indicates the maximum percentage error with respect to full scale deflection, as per IEC standards.
An ideal ammeter should have zero internal resistance. Non-zero internal resistance causes voltage drop and measurement error.
In electrical measurements, accuracy is typically expressed as a percentage of full scale deflection (FSD) or full scale reading (FSR) for analog instruments.
Ampere (A) is the SI base unit of electric current. It is defined as the flow of one coulomb of charge per second.
Modern VFDs support 0.1Hz to 500Hz+ output, enabling ultra-low speed precision applications and extended-speed motor operation.
MOSFETs have switching frequencies up to several MHz, while IGBTs typically reach 20-50kHz, thyristors <10kHz, and GTOs ~5kHz.
For a three-phase bridge rectifier: Vdc = (3√2/π) × Vline = 1.35 × 400 = 540V approximately.
Modern automotive DC-DC converters target 90-95% efficiency using advanced topologies, SiC MOSFETs, and optimized gate drives to minimize losses in 12V auxiliary systems.
Simultaneous conduction of upper switches creates a direct short across the DC link, causing massive current spike and potential device failure. This is prevented using dead-time insertion.
