### What is Voltage Regulation?

Voltage regulation is defined as the change in terminal voltage expressed as a fraction of full load rated voltage when the load at a given power factor is removed while keeping the speed and field current constant.

Voltage regulation formula,

Voltage regulation = (E_{F} – V_{T}) / V_{T} in P.U

% of Voltage regulation = (E_{F} – V_{T}) / V_{T} × 100

E_{F} = No-load excitation voltage

V_{T} = full load terminal voltage

Voltage regulation is always positive for lagging power factor load and E_{f} is always increasing. For obtaining the maximum voltage regulation load power factor angle (φ) must equal to impedance angle (ϴ). For leading power factor load, voltage regulation may be positive, zero, negative and E_{f} may decreases.

### Methods of Calculating voltage regulation

- The electromotive force (emf) method or synchronous impedance method
- MMF method (or) ampere turn method
- Zero power factor method
- S.A (American standards association) method.

Let we see,

**The electromotive force (emf) method or synchronous impedance method**: Even though this method gives the inconsistent result of voltage regulation it is quite useful because we consider drop due to armature reaction as drop due to synchronous reactance. It gives regulation more than actual value so it is called a pessimistic method.**MMF method (or) ampere turn method:**In MMF method, the reverse procedure is applied, i.e, each emf is replaced by an equivalent MMF. Here drop due to synchronous reactance is considered as drop due to armature reaction. It gives regulation less than actual value so it is called an optimistic method.**Zero power factor method:**It is also called a general method or Potier triangle method. Armature voltage and field currents are plotted and maintain the armature current at zero power factor lag called zero power factor characteristic.**S.A (American standards association) method:**This method is the combination of both MMF and zero power factor method.

Voltage Regulation For Transformer [Videos]: