**SI unit**

SI units are most widely used units of measurement belong to an international system of units which is also known as SI or Metric System.

**Shunt**

A precision resistor connected in parallel with a current indicating meter for the purpose of bypassing a specific fraction of current around the meter.

**Static Electricity**

Opposite static charges that occur when friction between two bodies causes electrons to transfer from one body to the other.

**Scalable digital multimeter**

A scalable digital multimeter is a device used to measure multiple electrical quantities knowing their initial values of voltage, current, and resistance.

**Series Circuit**

In series circuits, components are connected in such a way that same current flows through each component. However, the voltage drop across each element is different.

**Self-Inductance**

The phenomenon is which a changing current in a coil induces an emf in itself is called self-induction.

**Susceptance**

The reciprocal of circuit’s reactance, measured in Siemens; BL designates inductive reactance and BC capacitive susceptance.

**Semiconductor**

Material that lies midway between conductor and insulator in its ability to pass an electric current.

**Short Circuit**

An abnormal connection of very low resistance between two points of a circuit, resulting in a flow of excess current.

**Superposition Theorem**

Superposition Theorem states that in any linear network having more than one voltage source, the current and voltage in any one component of the network can be determined by algebraically adding the effect of each voltage source separately while all other sources are temporarily shorted.

**Specific Resistance**

The resistance of a conductor expressed in ohms per unit length per unit area, that is, per circular mil foot.

**Salient, or projecting, pole**

A ﬁeld pole that projects from the yoke or hub toward the primary winding core.

**Saturation curve**

A characteristic curve that expresses the degree of magnetic saturation as a function of some property of the magnetic excitation.

**Short-circuit characteristic (SCC)**

The relationship between the current in the short-circuited armature winding and the ﬁeld current.

Short-circuit test

A test applied to a transformer with one winding short-circuited and reduced voltage applied to the other winding such that rated current ﬂows in the windings.

**Single-phase transformer**

A device consisting of two or more windings coupled by a magnetic core that is used to transform a single-phase voltage.

**Skin effect**

The tendency of an alternating current to concentrate in the areas of lowest impedance.

**Slip RPM**

The difference between the synchronous speed and the actual speed of the rotor, expressed in revolution per minute (rpm).

## Slip s

The quotient of the difference between the synchronous speed and the actual speed of a rotor, to the synchronous speed, expressed as a ratio or percentage.

**Speed regulation**

The relationship between the speed and a load of a motor under specified conditions.

**Square matrix**

A matrix in which the number of rows is equal to the number of columns.

**Squirrel-cage rotor**

A rotor core assembly consisting of a number of conducting bars having their extremities connected by metal rings or plates at each end, like a squirrel’s cage.

**Stator**

The portion of the rotating machine that includes and supports the stationary active parts.

**Stranded conductor**

A conductor composed of a group of wires or of any combination of groups of wires.

**Swing equation**

The differential equation used to describe the dynamic motion of a synchronous machine.

**Synchronization**

The process whereby a synchronous machine, with its voltage and phase suitably adjusted, is paralleled with another synchronous machine or system.

**Synchronous machine**

A machine in which the average speed of normal operation is exactly proportional to the frequency of the system to which it is connected.

**Synchronous reactance**

The steady-state reactance of a generator during fault conditions used to calculate the steady-state fault current.

**Synchronous speed**

The speed of rotation of the magnetic ﬂux, produced by or linking the primary winding.

**Scientific notation**

A classification for representing a large or small number as a number between 1 and 10 times a power of ten.

**Strain gauge**

Transducer that changes its value based on an external force stretching or compressing it

**Sensor**

A device that converts a physical condition into an electrical signal for use by a controller, such as a PLC.

**Servo Motor**

It is a linear or rotary actuator that provides accurate control of linear or angular position, speed as well as acceleration. It comprises of an appropriate motor which is linked to a sensor in order to get position feedback.