Electrodynamometer Construction: Understanding the Instrument Type

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Questions and Answers

What is the relationship between the deflection and the power flowing through the Electrodynamometer Wattmeter?

The deflection is not related to the power.

The deflection is directly proportional to the power. (correct)

The deflection is proportional to the square of the power.

The deflection is inversely proportional to the power.

How is the current coil designed in the Electrodynamometer Wattmeter?

It carries approximately 40 Amperes.

It carries approximately 30 Amperes.

It carries approximately 10 Amperes.

It carries approximately 20 Amperes. (correct)

What is the purpose of the resistor connected in series with the moving coil?

To increase the voltage supply.

To increase the current flow.

To reduce the magnetic flux.

To control the flow of the current. (correct)

What type of control system is used in the Electrodynamometer Wattmeter?

Spring control system. Signup and view all the answers

What is the effect of air friction in the Electrodynamometer Wattmeter?

It decreases the pointer movement. Signup and view all the answers

What type of scale is used in the Electrodynamometer Wattmeter?

Linear scale. Signup and view all the answers

What is the primary advantage of electrodynamometer instruments over moving iron types?

Their calibration is less affected by variations in supply voltage, frequency, and waveforms Signup and view all the answers

What is the primary advantage of moving iron type power factor meters?

They are cheaper, simpler, and more robust Signup and view all the answers

What is the unique feature of the three-phase electrodynamometer type power factor meter?

It has two moving coils connected across two different phases Signup and view all the answers

What is the purpose of the series resistance in the three-phase electrodynamometer type power factor meter?

To provide a phase shift between the current and voltage Signup and view all the answers

What is the configuration of the fixed coil in the three-phase moving iron type power factor meter?

It is connected in series with a high resistance across one pair of lines Signup and view all the answers

What is the purpose of the sector-shaped vanes and pointer in the three-phase moving iron type power factor meter?

To measure the power factor Signup and view all the answers

What is the primary benefit of ensuring compliance with IEC standards for electrical equipment?

To meet internationally accepted technical specifications Signup and view all the answers

What is the primary purpose of training and certification for crew members responsible for switchgear and switchboards on ships?

To ensure competency and compliance with safety protocols Signup and view all the answers

Which of the following regulations may govern electrical installations on ships?

National or regional regulations, depending on the flag state and operating region Signup and view all the answers

Why are special starting procedures required for high-torque induction motors?

To prevent damage and ensure smooth acceleration Signup and view all the answers

What is the primary reason for ensuring motors accelerate quickly up to the predetermined speed?

To prevent excessively long run-up times and voltage dips Signup and view all the answers

What type of starters can be used to gradually start high-torque induction motors?

Soft starters Signup and view all the answers

What is the primary function of pump control?

To change the operation of pumps using controllers and actuators Signup and view all the answers

What is the purpose of a slip clutch in the Dreggen engine room crane hoisting machinery?

To provide overload protection and stop the hoist at the top and bottom positions Signup and view all the answers

What type of motor is used in the Engine room crane control?

Standard (induction) motor Signup and view all the answers

Why is a rack and pinion drive incorporated in the travel machinery of the Engine room crane?

To secure safe operation against 2 trim and 5 heel Signup and view all the answers

What is the function of the chain collection box in the Dreggen engine room crane hoisting machinery?

To collect the chain Signup and view all the answers

What type of starter can be used to automatically operate a pump?

Direct-on-line Starter Signup and view all the answers

What is the primary purpose of the service factor in generator protection?

To determine the actual maximum power of the machine Signup and view all the answers

What is the main reason for implementing overload current protection in generators?

To prevent damage from high starting currents of large motors Signup and view all the answers

What is the function of relays in over-current protection?

To cut power supplies to non-essential services on a preferential basis Signup and view all the answers

Which type of trip is commonly used in miniature circuit breakers (MCBs)?

Electromagnetic Trip Signup and view all the answers

What is the primary principle of operation of a thermal trip?

Bending action of a bimetallic strip Signup and view all the answers

What is the function of microprocessors in electronic over-current relays?

To process current signals and operate the circuit breaker Signup and view all the answers

Study Notes

Power Factor Meters

There are two types of power factor meters: Electrodynamometer and Moving Iron type
Electrodynamometer type meters are more accurate, but Moving Iron type meters are cheaper, simpler, and more robust
Moving Iron type meters have scales that extend 360 degrees, and all coils are fixed, eliminating ligaments

Three-Phase Electrodynamometer Type Power Factor Meter

Only useful for balanced loads
Two moving coils are placed at an angle of 120 degrees to each other
Each coil has a series resistance and is connected to two different phases of the supply circuit
No phase splitting is required, as the required phase displacement can be obtained from the supply itself

Three-Phase Moving Iron Type Power Factor Meter

Has a fixed coil connected in series with a high resistance across one pair of lines
Coil is in the center of three fixed coils, each connected to lines 1, 2, and 3 respectively
Compliance with IEC standards ensures electrical equipment meets internationally accepted technical specifications

Training and Certification Requirements

Crew members operating, maintaining, or repairing switchgear and switchboards on ships must receive training and certification to ensure competency and compliance with safety protocols
National and regional regulations, such as USCG regulations and EU directives, govern electrical installations on ships

Starters for Alternating Current Motors

Special high-torque induction motors require careful starting procedures to prevent damage
Soft starters can be used to gradually start motors, ensuring smooth acceleration and reduced stress on motor windings
Approximate full-load currents for 3-phase motors of average efficiency must be considered

Over-Current Protection

Generators require circuit breakers for long-time delay over-current protection, limited to 15% above their full-load or overload rating
Overload current can result from increased switchboard loads, unnoticed operation of large systems, or serious faults
Over-current protection is achieved through relays, breaker overload current trips, and instantaneous short-circuit current tripping

Types of Trip

Electromagnetic Trip: uses a solenoid to operate a 'trip' switch
Thermal Trip: uses a bimetallic strip to trip the circuit breaker
Electronic Trip: converts current into a proportional voltage and uses microprocessors to process current signals

Construction of Electrodynamometer Wattmeter

Fixed coil is connected in series with the load and is divided into two parts for easy construction
Moving coil is connected parallel with the supply voltage and has a pointer mounted on it
Temperature increases when current flows through the coil, so a resistor is connected in series to control the flow of current

Control and Damping

Control provides controlling torque onto the instrument, with gravity control and spring control being the two types
Electrodynamometer wattmeters use a spring control system to help the pointer movement
Damping reduces the pointer movement, with air friction being used to produce damping torque

Scales and Pointers

Linear scale is used, as the moving coil moves linearly
Short circuit protection must be provided by fuses or a circuit breaker on the supply side of the starter

Remote Control Pump Control

Pump control refers to changing how pumps operate using pump controllers and actuators
Direct-on-line Starter can be automatically operated using a float switch

Engine Room Crane Control

Engine room crane is an indispensable piece of equipment on a ship
Various types of cranes exist, ranging from simple two-motor-single-speed type to three-motor-dual-speed type
Speed control of standard induction motors can be achieved using special-purpose motor and electronic cards

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Description

Learn about the construction and working of electrodynamometer wattmeter, including its fixed and moving coils, and how it produces a uniform electric field. Understand the design of the current coil and its importance in the measurement of power.

Electrodynamometer Wattmeter: Construction and Working