# Why Does Increasing Steam Input to an Alternator Increase the Load Angle?

• kuchun
In summary: Load angle is also called "load vector angle" or "rotor field angle". As you can see, it depends on the load - so it's not just a simple angle between stator and rotor.
kuchun
After going through the chapter of Alternator (i.e Synchronous Generator) I have come to know that if the steam input to the turbine which is coupled to the rotor shaft of the alternator is increased the load angle will increase.. but what is the reason behind this ? I want to know both mathematical and physical explanation. What is the significance of load angle and why is it also called the torque angle ? Please help me to understand these things.
Thank you

Noaha
kuchun said:
After going through the chapter of Alternator (i.e Synchronous Generator) I have come to know that if the steam input to the turbine which is coupled to the rotor shaft of the alternator is increased the load angle will increase.. but what is the reason behind this ? I want to know both mathematical and physical explanation. What is the significance of load angle and why is it also called the torque angle ? Please help me to understand these things.
Thank you

Considering a synchronous generator connected to a power grid - we have fixed frequency and voltage of our machine. Also the excitation voltage is assumed const.

Now, if You change the amount of steam send to turbine You will change the torque driving the generator. Torque of a generator can be described as:

(1) T=c*((Vs*Vr)/Xd)*sin(theta)

T-torque; c-some constant; Vs-stator voltage; Vr-rotor (excitation) voltage; theta-load angle
Assuming as said above, change of driving torque will affect the load angle (theta).

So much for a math. Now, load angle is a angle between the stator and rotor fields. In general the theta can change from -90 to + 90 deg. In practice it's much smaller (20-40 deg at rated load).
The load angle is very important - it's closely connected with real and imaginary power generated by a generator. It must be kept in allowed range of each individual type of generator (to stay in synchronism and not allow excessive stator core end-region losses). There is much more about this to say..

Physical explanation (in some BIG simplification):
Everyone knows how to calculate force on a wire in a magnetic field:

(2) F=c*I*B*sin(alfa)
F-force; c-some constant; I-current caried by a conductor; B-induction of a field; alfa-angle between field vector and wire with a current

We can treat synch. generator like a rotating wire excited with a current and rotating magnetic field (both rotating same direction and speed - in synchronism).

This equation (2) can be transferred to a rotating system - then we'll have torque instead of a force. Maximum torque can be observed at +/- 90 deg (just like maximum torque of a generator). In this rotating system (much simplified!) we provide driving torque to the wire. The angle between wire and magnetic field will change (load-torque angle) so bigger torque (2) will counteract driving torque. It's all fine when alfa is in +/-90 deg range (synch. mode). I hope that is clear.

Last thing, power and torque are connected:

(3) P=T*omega

P-power; T-torque; omega-rotating speed of machine (fixed by grid frequency)

I hope now it's clear why load angle is called torque angle (it depends on the load thus torque).

## What is the load angle of an alternator?

The load angle of an alternator is the angle between the rotor magnetic field and the stator magnetic field. It is also known as the power angle or torque angle.

## How is the load angle of an alternator determined?

The load angle of an alternator is determined by the amount of mechanical load on the rotor and the strength of the magnetic fields in the rotor and stator. It can be calculated using mathematical equations or measured using specialized equipment.

## What is the significance of the load angle in an alternator?

The load angle is an important factor in the performance of an alternator. It determines the amount of power that can be generated by the alternator and can also affect the stability of the power system.

## How does the load angle affect the efficiency of an alternator?

The load angle can impact the efficiency of an alternator by affecting the amount of power it can produce. A high load angle can decrease the efficiency of the alternator as it requires more mechanical energy to produce the same amount of electrical power.

## What factors can affect the load angle of an alternator?

The load angle of an alternator can be affected by various factors such as changes in the mechanical load, variations in the strength of the magnetic fields, and the operating speed of the alternator. Changes in these factors can cause fluctuations in the load angle and consequently impact the performance of the alternator.

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