Exam Question
(a) Sketch and describe a power (watt) meter for an a.c. switchboard. (8)
(b) State what type of load governs power factor and give examples of power factor for a resistance load and for normal marine operation. (8)
Class 4 (4th Engineer)
MET
📅 May 2024
Reference Answer
### (a) Sketch and Describe a Power (Watt) Meter for an A.C. Switchboard
A wattmeter is an instrument used to measure the true electrical power (in Watts) in an AC circuit. The most common type used in marine switchboards is the electrodynamic (or dynamometer) wattmeter, which operates based on the interaction of magnetic fields produced by current and voltage coils.
#### **1. Principle of Operation**
The operating principle is based on the force exerted between a magnetic field produced by a stationary coil and a magnetic field produced by a moving coil. The torque that causes the moving coil to deflect is directly proportional to the product of the instantaneous current flowing through the load and the instantaneous voltage across the load.
A wattmeter is an instrument used to measure the true electrical power (in Watts) in an AC circuit. The most common type used in marine switchboards is the electrodynamic (or dynamometer) wattmeter, which operates based on the interaction of magnetic fields produced by current and voltage coils.
#### **1. Principle of Operation**
The operating principle is based on the force exerted between a magnetic field produced by a stationary coil and a magnetic field produced by a moving coil. The torque that causes the moving coil to deflect is directly proportional to the product of the instantaneous current flowing through the load and the instantaneous voltage across the load.
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