Hello friends, I hope all of you are fine. In today’s tutorial, we are gonna have a look at the Power and Torque in Synchronous Generator and their relationship. The synchronous generator is an apparatus that alters mechanical energy into electrical energy. To move its shaft there are many sources like steam turbines, petrol engines or water turbines that provided mechanical energy to the generator. These sources of mechanical power are named as a prime mover.

It does not matter which prime mover we are using; the main thing is that it should rotate the rotor at a constant speed irrespective of the variation in the power demand. If the prime mover does not deliver the continuous speed, then the frequency of the power generated by the generator will not be the same. In today’s post, we will have a look at the relation between torque and power of the synchronous generator. so let’s get started with the power and torque in the synchronous generator.

Power and Torque in Synchronous Generator

• The mechanical power provided by the prime mover to the synchronous generator does not transform into electrical power completely.
• The mechanical power that does not convert into electric energy is called loss power.
• The power flow diagram of the synchronous generator is described below.
• The power provided by the prime mover to generator is.

P_in = T_appw_m

• Whereas, this input power converted to the electricity is given here.

P_con = T_indw_m

P_con = 3E_AI_Acosγ

• In this equation, the E_A is the internally generated voltage of the generator and I_A is the armature current, γ  is the angle between them.
• The power that does not convert into the electric energy is wasted in the form of core losses that are eddy current and hysteresis loss, iron loss, windage and friction losses.

Power of the Synchronous Generator

• The out power of the generator that is electrical power can be written as.

P_out =√3 V_TI_L Cosø

• It can be written in phase form.

P_out =3 V_øI_A Cosø—-(1)

• The reactive power of the generator can be defined as

Q_out =√3 V_TI_L Sinø

• It can also write in phase form.

Q_out =3 VøI_A Sinø

• As the Xs>>R_A, so if we neglected the armature resistance (R_A) then a very valuable expression can b finds to define the P_out of the synchronous generator.
• To find this expression we study the given phasor diagram.

• It is the simple phasor diagram of the generator without the armature resistance.
• From a diagram, you can see that the bc portion has the value of E_Asinor X_sI_Acosø.
• so, we have

I_Acosø = E_Asinδ/X_s

• If we put this expression in the equation (1) then we have.

P=3 Vø E_Asinδ/X_s——- (2)

• As there is no resistance in the equation (2) so there is no loss in the generator and this equation is for input and the output of the generator.
• From equation (2) we can observe that the output power of the synchronous generator depends on the angle (δ) among the internal generated voltage E_A and the phase (terminal) voltage of the generator.
• The angle (δ) is also called the torque angle of the synchronous generator.
• The extreme power that can generator produced will be given when the value of torque angle (δ) is ninety degrees.
• When δ =90⁰, sin =1, so the power will be.

P_max =3V_øE_A/X_s —- (3)

• The maximum power given in this equation is known as the static stability limit of the generator.
• Usually, practically no generator reaches this limit.
• If we observe given below equation again.

P_out =3 V_øI_A Cosø—-(1)

Q_out =3 V_øI_A Sinø

P=3 Vø E_Asinδ/X_s——- (2)

• Let’s suppose that the V_ø in these three equations is constant than the outputs of the active powers are directly proportionate to the I_A Cosø and the E_A Sinø and the reactive power (Q) is proportionate to the I_A Sinø.
• These factors are beneficial for the construction of the phasor diagram of the generator when the load varies.

Torque in Synchronous Generator

• As we know that the torque in the synchronous machine is given as.

T_ind =KB_R x B_S

T_ind =KB_R x B_net—-(d)

• The magnitude of the equation (d) can be written as.

T_ind =KB_RB_netsinδ

• In this equation the δ is the angle among the field of the rotor (B_R) and the net field of the generator (B_net), it is known as the torque angle.
• Another equation for the torque can be calculated by this equation.

P=3 Vø E_Asinδ/X_s

• As we know that the converted power (P_conv) = T_indw_m, so the induced torque of the synchronous generator is.

T_ind= 3 Vø E_Asinδ/w_mX_s ——(f)

• Equation ‘f’ gives the value of the torque in the form of electric numbers but the given below equation gives the torque in the form of magnetic terms.

T_ind =KB_RB_netsinδ

You can also read some related topics to synchronous generators that are listed here.

Importance of Torque in Synchronous Generators

Torque basic factor of synchronous generators, since it directly affects the ability to produce power. The magnitude and type of torque produced are important to finding the load capacity of the generator, stability and overall performance.

Types of Torque in a Synchronous Generator

1. Starting Torque

Starting torque is the minimum value of torque needed to start the rotation of a static generator. important for the generator starting process

2. Pull-out Torque

Pull-out torque defines the highest torque synchronous generator can handle without the loss of synchronization with the grid

3. Maximum Torque

It is the highest rotational force that a generator can bear before getting its mechanical limits

4. Synchronous Torque

Synchronous torque is the steady-state torque required to maintain the synchronism of the generator with the grid at a certain load condition

5. Load Torque

it is the opposing torque bear by the generator when attached to the load. It finds the generator’s ability to provide power to different loads

6. Breakdown Torque

it is the maximum torque a generator can handle without facing mechanical failure.

7. Pull-in Torque

Pull-in torque is the torque needed to bring the generator into synchronization if it loses synchronism during work.

Factors Affecting Torque Production

1. Magnetic Field Strength

The strength of the magnetic field in the generator highly affects the torque generation ability.

2. Rotor Speed

The rotational speed of the rotor generator affects produced torque value.

3. Rotor Design and Construction

The design and manufacturing of the rotor are important to determining the torque features of the generator.

4. Load Conditions

The type and magnitude of the attached load affect the torque needs and performance.

5. Temperature

Temperature changes can affect the conductivity of the  components of the generator, consequently affecting the torque generated

6. Supply Voltage

The voltage provided to the generator has an impact on the magnitude of the generated torque.

Torque Control Methods

1. Field Current Control

The adjustment of field current provides accurate control over then the output of the generator torque

2. Armature Current Control

Controlling the armature current helps to manage the torque in varying load conditions.

3. Voltage Control

Voltage control is the best method to handle torque variations in the generator

4. Slip Test Method

The slip test method helps in evaluating the torque characteristics of the generator under different operating conditions.

Efficiency and Losses in Torque Generation

1. Copper Losses

Copper losses cause due to resistance of windings and result in a decrement in torque efficiency

2. Iron Losses

Iron losses are produced by the magnetic features of the core materials and can impact torque generation

3. Mechanical Losses

Mechanical losses, like friction and windage losses, help to reduce overall torque efficiency.

4. Stray Load Losses

Stray load losses are energy losses in different components like bearings and shafts, decreasing the effective torque.

5. Power Factor and its Impact on Torque Efficiency

The power factor of the generator can impact the torque efficiency and, in result, overall electrical performance.

Introduction to Synchronous Generator

Synchronous Generator Equivalent Circuit  

Synchronous Generator Phasor Diagram

Synchronous Generator Parameters

Synchronous Generator Operating Alone

Synchronous Generator Parallel Operation

Synchronous Generator parallel with Large Power system

Synchronous Generator Parallel with same Size Generator

Synchronous Generator Ratings

Synchronous Generator Capability Curves

Synchronous Generator Transients

That is the complete article on power and torque of synchronous generator if you want to know something more ask in comments. See you in the next tutorial Synchronous Generator Parameter.