Critical field resistance is a term that is associated with a
shunt DC generator. In a DC shunt generator, the
voltage
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...
induced across the
armature, V
a, is directly proportional to the
flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...
acting across it, The flux in a DC generator is directly proportional to the
field current
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a electric motor, motor or electrical generator, generator. It consists of a coil of wire through ...
, I
f. The critical field resistance is defined as the maximum field circuit resistance (for a given
speed
In kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. Intro ...
) with which the shunt generator would just excite. The shunt generator will build up voltage only if field circuit resistance is less than critical field resistance.
It is a
tangent
In geometry, the tangent line (or simply tangent) to a plane curve at a given point is, intuitively, the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points o ...
to the open-circuit characteristics of the generator (at a given speed).
References
* Electrical Technology - II by B.L. Thereja
External links
DC Machines
{{DEFAULTSORT:Critical Field Resistance
Electric motors
Electrical generators