
- Electrical Machines - Home
- Basic Concepts
- Electromechanical Energy Conversion
- Energy Stored in Magnetic Field
- Singly-Excited and Doubly Excited Systems
- Rotating Electrical Machines
- Electrical Machines Types
- Faraday’s Laws of Electromagnetic Induction
- Concept of Induced EMF
- Fleming's Left Hand and Right Hand Rules
- Transformers
- Electrical Transformer
- Construction of Transformer
- EMF Equation of Transformer
- Turns Ratio and Voltage Transformation Ratio
- Ideal Transformer
- Practical Transformer
- Ideal and Practical Transformers
- Transformer on DC
- Losses in a Transformer
- Efficiency of Transformer
- 3-Phase Transformer
- Types of Transformers
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- Transformer Working Principle
- Single-Phase Transformer Working Principle
- 3-Phase Transformer Principle
- 3-Phase Induction Motor Torque-Slip
- 3-Phase Induction Motor Torque-Speed
- 3-Phase Transformer Harmonics
- Double-Star Connection (3-6 Phase)
- Double-delta Connection (3-6 Phase)
- Transformer Ratios
- Voltage Regulation
- Delta-Star Connection (3-Phase)
- Star-Delta Connection (3-Phase)
- Autotransformer Conversion
- Back-to-back Test (Sumpner's Test)
- Transformer Voltage Drop
- Autotransformer Output
- Open and Short Circuit Test
- 3-Phase Autotransformer
- Star-Star Connection
- 6-Phase Diametrical Connections
- Circuit Test (Three-Winding)
- Potential Transformer
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- Autotransformer
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- No-Load Current Wave
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- Transformer Vector Groups
- 3 to 12-Phase Transformers
- Scott-T Transformer Connection
- Transformer kVA Rating
- Three-Winding Transformer
- Delta-Delta Connection Transformer
- Transformer DC Supply Issue
- Equivalent Circuit Transformer
- Simplified Equivalent Circuit of Transformer
- Transformer No-Load Condition
- Transformer Load Condition
- OTI WTI Transformer
- CVT Transformer
- Isolation vs Regular Transformer
- Dry vs Oil-Filled
- DC Machines
- Construction of DC Machines
- Types of DC Machines
- Working Principle of DC Generator
- EMF Equation of DC Generator
- Derivation of EMF Equation DC Generator
- Types of DC Generators
- Working Principle of DC Motor
- Back EMF in DC Motor
- Types of DC Motors
- Losses in DC Machines
- Applications of DC Machines
- More on DC Machines
- DC Generator
- DC Generator Armature Reaction
- DC Generator Commutator Action
- Stepper vs DC Motors
- DC Shunt Generators Critical Resistance
- DC Machines Commutation
- DC Motor Characteristics
- Synchronous Generator Working Principle
- DC Generator Characteristics
- DC Generator Demagnetizing & Cross-Magnetizing
- DC Motor Voltage & Power Equations
- DC Generator Efficiency
- Electric Breaking of DC Motors
- DC Motor Efficiency
- Four Quadrant Operation of DC Motors
- Open Circuit Characteristics of DC Generators
- Voltage Build-Up in Self-Excited DC Generators
- Types of Armature Winding in DC Machines
- Torque in DC Motors
- Swinburne’s Test of DC Machine
- Speed Control of DC Shunt Motor
- Speed Control of DC Series Motor
- DC Motor of Speed Regulation
- Hopkinson's Test
- Permanent Magnet DC Motor
- Permanent Magnet Stepper Motor
- DC Servo Motor Theory
- DC Series vs Shunt Motor
- BLDC Motor vs PMSM Motor
- Induction Motors
- Introduction to Induction Motor
- Single-Phase Induction Motor
- 3-Phase Induction Motor
- Construction of 3-Phase Induction Motor
- 3-Phase Induction Motor on Load
- Characteristics of 3-Phase Induction Motor
- Speed Regulation and Speed Control
- Methods of Starting 3-Phase Induction Motors
- More on Induction Motors
- 3-Phase Induction Motor Working Principle
- 3-Phase Induction Motor Rotor Parameters
- Double Cage Induction Motor Equivalent Circuit
- Induction Motor Equivalent Circuit Models
- Slip Ring vs Squirrel Cage Induction Motors
- Single-Cage vs Double-Cage Induction Motor
- Induction Motor Equivalent Circuits
- Induction Motor Crawling & Cogging
- Induction Motor Blocked Rotor Test
- Induction Motor Circle Diagram
- 3-Phase Induction Motors Applications
- 3-Phase Induction Motors Torque Ratios
- Induction Motors Power Flow Diagram & Losses
- Determining Induction Motor Efficiency
- Induction Motor Speed Control by Pole-Amplitude Modulation
- Induction Motor Inverted or Rotor Fed
- High Torque Cage Motors
- Double-Cage Induction Motor Torque-Slip Characteristics
- 3-Phase Induction Motors Starting Torque
- 3-phase Induction Motor - Rotor Resistance Starter
- 3-phase Induction Motor Running Torque
- 3-Phase Induction Motor - Rotating Magnetic Field
- Isolated Induction Generator
- Capacitor-Start Induction Motor
- Capacitor-Start Capacitor-Run Induction Motor
- Winding EMFs in 3-Phase Induction Motors
- Split-Phase Induction Motor
- Shaded Pole Induction Motor
- Repulsion-Start Induction-Run Motor
- Repulsion Induction Motor
- PSC Induction Motor
- Single-Phase Induction Motor Performance Analysis
- Linear Induction Motor
- Single-Phase Induction Motor Testing
- 3-Phase Induction Motor Fault Types
- Synchronous Machines
- Introduction to 3-Phase Synchronous Machines
- Construction of Synchronous Machine
- Working of 3-Phase Alternator
- Armature Reaction in Synchronous Machines
- Output Power of 3-Phase Alternator
- Losses and Efficiency of an Alternator
- Losses and Efficiency of 3-Phase Alternator
- Working of 3-Phase Synchronous Motor
- Equivalent Circuit and Power Factor of Synchronous Motor
- Power Developed by Synchronous Motor
- More on Synchronous Machines
- AC Motor Types
- Induction Generator (Asynchronous Generator)
- Synchronous Speed Slip of 3-Phase Induction Motor
- Armature Reaction in Alternator at Leading Power Factor
- Armature Reaction in Alternator at Lagging Power Factor
- Stationary Armature vs Rotating Field Alternator Advantages
- Synchronous Impedance Method for Voltage Regulation
- Saturated & Unsaturated Synchronous Reactance
- Synchronous Reactance & Impedance
- Significance of Short Circuit Ratio in Alternator
- Hunting Effect Alternator
- Hydrogen Cooling in Synchronous Generators
- Excitation System of Synchronous Machine
- Equivalent Circuit Phasor Diagram of Synchronous Generator
- EMF Equation of Synchronous Generator
- Cooling Methods for Synchronous Generators
- Assumptions in Synchronous Impedance Method
- Armature Reaction at Unity Power Factor
- Voltage Regulation of Alternator
- Synchronous Generator with Infinite Bus Operation
- Zero Power Factor of Synchronous Generator
- Short Circuit Ratio Calculation of Synchronous Machines
- Speed-Frequency Relationship in Alternator
- Pitch Factor in Alternator
- Max Reactive Power in Synchronous Generators
- Power Flow Equations for Synchronous Generator
- Potier Triangle for Voltage Regulation in Alternators
- Parallel Operation of Alternators
- Load Sharing in Parallel Alternators
- Slip Test on Synchronous Machine
- Constant Flux Linkage Theorem
- Blondel's Two Reaction Theory
- Synchronous Machine Oscillations
- Ampere Turn Method for Voltage Regulation
- Salient Pole Synchronous Machine Theory
- Synchronization by Synchroscope
- Synchronization by Synchronizing Lamp Method
- Sudden Short Circuit in 3-Phase Alternator
- Short Circuit Transient in Synchronous Machines
- Power-Angle of Salient Pole Machines
- Prime-Mover Governor Characteristics
- Power Input of Synchronous Generator
- Power Output of Synchronous Generator
- Power Developed by Salient Pole Motor
- Phasor Diagrams of Cylindrical Rotor Moto
- Synchronous Motor Excitation Voltage Determination
- Hunting Synchronous Motor
- Self-Starting Synchronous Motor
- Unidirectional Torque Production in Synchronous Motor
- Effect of Load Change on Synchronous Motor
- Field Excitation Effect on Synchronous Motor
- Output Power of Synchronous Motor
- Input Power of Synchronous Motor
- V Curves & Inverted V Curves of Synchronous Motor
- Torque in Synchronous Motor
- Construction of 3-Phase Synchronous Motor
- Synchronous Motor
- Synchronous Condenser
- Power Flow in Synchronous Motor
- Types of Faults in Alternator
- Miscellaneous Topics
- Electrical Generator
- Determining Electric Motor Load
- Solid State Motor Starters
- Characteristics of Single-Phase Motor
- Types of AC Generators
- Three-Point Starter
- Four-Point Starter
- Ward Leonard Speed Control Method
- Pole Changing Method
- Stator Voltage Control Method
- DOL Starter
- Star-Delta Starter
- Hysteresis Motor
- 2-Phase & 3-Phase AC Servo Motors
- Repulsion Motor
- Reluctance Motor
- Stepper Motor
- PCB Motor
- Single-Stack Variable Reluctance Stepper Motor
- Schrage Motor
- Hybrid Schrage Motor
- Multi-Stack Variable Reluctance Stepper Motor
- Universal Motor
- Step Angle in Stepper Motor
- Stepper Motor Torque-Pulse Rate Characteristics
- Distribution Factor
- Electrical Machines Basic Terms
- Synchronizing Torque Coefficient
- Synchronizing Power Coefficient
- Metadyne
- Motor Soft Starter
- CVT vs PT
- Metering CT vs Protection CT
- Stator and Rotor in Electrical Machines
- Electric Motor Winding
- Electric Motor
- Useful Resources
- Quick Guide
- Resources
- Discussion
Hydrogen Cooling of a Synchronous Generator or Alternator
Hydrogen gas is used as cooling medium for cooling the alternators because of its superior cooling properties. The hydrogen cooling of the alternators requires completely seated circulated system. Mainly, oil-seated glands are used between shaft and casing of the alternator. The oil absorbs both hydrogen leaking-out and air leaking-in, so it should be purified periodically.
In the hydrogen cooling of the alternators, the hydrogen gas is circulated by blowers and fans through the stator and rotor. Then, the heated hydrogen gas is passes over cooling coils inside the seated casing. The cooling coils carry oil or water to extract the heat from the circulating hydrogen.
The main reason that justifies the use of hydrogen cooling is that, it increases the capacity of the alternator by about 25% of the alternator of the same physical size using air cooling. Also, the hydrogen cooling increases the full-load efficiency of the alternator by about 1%.
Advantages of Hydrogen Cooling of Alternator
The hydrogen cooling of alternators has following advantages over the air-cooling −
- Cooling with the hydrogen gas is faster. Since the hydrogen gas has a higher thermal conductivity and 1.5 times heat transfer capacity as compared to the air.
- Hydrogen gas has low-density than air at the same temperature and pressure. Therefore, when the hydrogen cooling is used in the alternator, windage loss and noise produced in the machine is reduced because, the revolving parts rotate in the low-density hydrogen. Also, the efficiency of the alternator increases.
- When air-cooling is used in the alternators, corona discharge may take place to produce ozone, oxides of nitrogen, nitric acid, etc., which damage the insulation of the alternator. Whereas, with the hydrogen cooling, the corona does not occur and hence the life of the insulation of the alternator being increased.
Precautions with Hydrogen Cooling
Certain mixtures of hydrogen and air are explosive. Explosion may take place with a range of 6% hydrogen gas and 94% air up to 71% hydrogen gas and 29% air. When the hydrogen gas is more than 71% in the mixture, then the mixture is neither combustible nor supports combustion. In practice, 9:1 ratio of hydrogen to air is used in very large alternators.
Also, in order to prevent the explosion of the mixture of hydrogen and air in the alternator, the pressure of the hydrogen gas should be maintained above the atmospheric pressure to prevent inward seepage of contaminated air.
Limitations of Hydrogen Cooling of Alternator
Following are the limitations of the hydrogen cooling used in the alternators or synchronous generators −
- Because of the necessity to provide explosion proof construction and gas-tight shaft seals, the hydrogen-cooled alternators have expensive frame than the air-cooled alternators.
- Cooling coils carrying oil or water inside the casing are to be provided to extract the heat from the circulating hydrogen.
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Means are necessary to admit hydrogen gas to the alternator without creating explosion. There are two ways to achieve this −
- Purifying the air with CO2 and then admitting the hydrogen gas.
- By vacuum pumping the unit to of the atmospheric pressure and then admitting the hydrogen gas.