Compared to the MMF method, the EMF method is ___________.

EMF method versus MMF method of voltage regulation of the alternator

• The EMF method (also known as the synchronous impedance method) simplifies the analysis by assuming a constant synchronous impedance Z_S.
• This assumption does not account for saturation and changes in armature reaction, making it less accurate than the MMF method, which considers the actual magnetizing force required for both the air gap and core under load.
• The MMF method more accurately reflects non-linearities like magnetic saturation and is generally preferred for precise voltage regulation calculations.
   

Methods for determining the voltage regulation of the alternator

Ampere turn method (MMF method):

• The voltage regulation calculated using the MMF method will always be lower than the actual voltage regulation of an alternator; that's why it is known as the optimistic method.
• The MMF method replaces the effect of armature leakage reactance with an equivalent additional armature reaction MMF so that this MMF may be combined with the armature reaction MMF.
   

Synchronous impedance method (EMF method):

• The voltage regulation calculated using the EMF method will always be higher than the actual voltage regulation of an alternator; that's why it is known as the pessimistic method.
• The synchronous impedance method is based on the concept of replacing the effect of an armature reaction with an imaginary reactance.
   

Potier triangle method (Zero Power Factor Method):

The following assumptions are made in the Potier triangle method:

• The armature reaction MMF is constant.
• The open-circuit characteristic (O.C.C.) taken on no-load accurately represents the relation between MMF and voltage under loaded conditions.
• The voltage drop due to the armature leakage reactance (la XaL) is independent of the excitation.