JJWalecka
Senior Member
- Location
- New England
American Electricians Handbook. Page 1.52 & 1.53
?Effective values of alternating current and voltage are the ones ordinarily referred to when we speak of alternating quantities. Alternating voltages and currents are constantly changing in value, with certain rang, from instant to instant even if the load is constant. It is not practicable to deal with or indicate with instruments these constantly changing values. The effective value of an alternating current or voltage is the value of a direct current or voltage that would have the same heating effect. A sinusoidal alternating current which has a maximum value of14.14 A will have the same heating effect as a 10 A direct current. The effective value of the alternating current is therefore 10 A. Practical people deal almost exclusively with effective values. The relation between effective and maximum values for sinusoidal quantities is given below and illustrated in Fig. 1.40. Effective value is also referred to as rms (root means squared) value.?
?Effective value =0.707 x maximum value
Maximum value = effective value/ 0.707?
Page 3.16 mentions effect of increased voltages on various equipment. The following is one subject that was addressed.
?Generators
Increase in excitation
Will the exciter voltage be sufficient to produce the required excitation at full load or at practical load of low power factor?
Will the fields overheat at the increased excitation required?
Increase in core loss.
Will the iron overheat?
Decrease in armature copper loss for same kilovolt-ampere output.
Will this offset the additional field and core loss??
Do engineers deal with the maximum value when designing equipment?
Equipment is rated for 277V/480V.
The maximum value of 480V is 678.92V.
Obviously the engineer would compensate for the higher voltage.
Any feedback and insight would be appreciated.
Perhaps I am over thinking this. Thank you.
Justin J. Walecka
?Effective values of alternating current and voltage are the ones ordinarily referred to when we speak of alternating quantities. Alternating voltages and currents are constantly changing in value, with certain rang, from instant to instant even if the load is constant. It is not practicable to deal with or indicate with instruments these constantly changing values. The effective value of an alternating current or voltage is the value of a direct current or voltage that would have the same heating effect. A sinusoidal alternating current which has a maximum value of14.14 A will have the same heating effect as a 10 A direct current. The effective value of the alternating current is therefore 10 A. Practical people deal almost exclusively with effective values. The relation between effective and maximum values for sinusoidal quantities is given below and illustrated in Fig. 1.40. Effective value is also referred to as rms (root means squared) value.?
?Effective value =0.707 x maximum value
Maximum value = effective value/ 0.707?
Page 3.16 mentions effect of increased voltages on various equipment. The following is one subject that was addressed.
?Generators
Increase in excitation
Will the exciter voltage be sufficient to produce the required excitation at full load or at practical load of low power factor?
Will the fields overheat at the increased excitation required?
Increase in core loss.
Will the iron overheat?
Decrease in armature copper loss for same kilovolt-ampere output.
Will this offset the additional field and core loss??
Do engineers deal with the maximum value when designing equipment?
Equipment is rated for 277V/480V.
The maximum value of 480V is 678.92V.
Obviously the engineer would compensate for the higher voltage.
Any feedback and insight would be appreciated.
Perhaps I am over thinking this. Thank you.
Justin J. Walecka
