Idle Current Reduction: A step motor driver feature that reduce the phase current to the motor when no motor motion is commanded (idle condition) for a specified period of time. Idle current reduction reduces motor heating and allows high machine throughputs from a given motor.

Incremental: Refers to an output that is measured in known increments from a known reference point; e.g., a step motor provides incremental motion based on an initial position and an incremental encoder provides incremental feedback information based on a known zero point.

Incremental Encoder: An incremental encoder is a device which provides a series of periodic signals due to mechanical motion. The number of successive cycles (signals) corresponds to the resolvable mechanical increments of motion.

Incremental Measuring System: Measuring method by which the measuring value is derived by the summation (counting) of increments (measuring steps).

Index (Marker): The index is a separate output signal generated by a special track which produces a single pulse (or transition change) at a unique position on the disk. The index is typically used to identify a center, home position, reset point, or zero reference.

Indexer: Electronics which convert high level motion commands from a host computer, PLC or operator panel into step and direction pulse streams for use by the step motor driver. Indexers can be broadly divided into two classes. A preset indexer typically accepts distance, velocity and ramp time inputs only. The more sophisticated programmable indexer is capable of complex motion control and includes program memory.

Inductance (L) (mH - millihenries line-to-line) : The electrical equivalent to mechanical inertia; that is, the property of a circuit, which has a tendency to resist current flow when no current is flowing, and when current is flowing has a tendency to maintain that current flow.

Inductance (mutual): Mutual inductance is the property that exists between two current carrying conductors or coils when magnetic lines of force from one link with those of the other.

Induction Motor: An induction motor is an alternating current motor in which the primary winding on one member (usually the stator) is connected to the power source and a secondary winding or a squirrel-cage secondary winding on the other member (usually the rotor) carries the induced current. There is no physical electrical connection to the secondary winding, its current is induced.

Inertia: The property of an object to resist change in velocity unless acted upon by an outside force. Higher inertia objects require larger torques to accelerate and decelerate. Inertia is dependent upon the mass and shape of the object.

Inertial Load: A load (flywheel, fan, etc.) which tends to cause the motor shaft to continue to rotate after the power has been roved (stored kinetic energy). If this continued rotation cannot be tolerated, some mechanical or electrical braking means must be applied. This application may require a special motor due to the energy required to accelerate the inertia. Inertia is measured in either lb.-ft.2 or oz.-in.2

Inertial Match: For most efficient operation, the system coupling ratio should be selected so that the reflected inertia of the load is equal to the rotor inertia of the motor.

Insulation Class: The rating assigned to the maximum temperature capability of the insulating components in a motor or other piece of equipment.

Insulation System: Five specialized elements are used, which together constitute the motor's Insulation System. The following are typical in an AC motor: 1. TURN-TO-TURN INSULATION between separate wires in each coil. Usually enamel to random wound coils of smaller motors – tape on form wound coils of larger motors. 2. PHASE-TO-PHASE INSULATION between adjacent coils in different phase groups. A separate sheet material on smaller motors – not required on form wound coils because the tape also performs this function. 3. PHASE-TO-GROUND INSULATION between windings as a whole and the ground or metal part of the motor. A sheet material, such as the liner used in stator slots, provides both dielectric and mechanical protection. 4. SLOT WEDGE to hold conductors firmly in the slot. 5. IMPREGNATION to bind all the other components together and fill in the air space.

Insulator: A material which tends to resist the flow of electric current (paper, glass, etc.). In a motor the insulation serves two basic functions: 1. Separates the various electrical components from one another. 2. It protects itself and the electrical components from attack of contaminants and other destructive forces.

Integral Coupling: Innovative angle encoder design with built-in coupling, located preferably on the stator-side.

Interferential Measuring System: Photoelectric measuring system with a phase grating scale where scanning signals are produced via the interference of diffracted beams.

Intermittent Duty: A requirement of service that demands operation for alternate intervals of (1) load and no load; or (2) load and rest; (3) load, no load and rest; such alternative intervals being definitely specified.

Interpoles: An auxiliary set of field poles carrying armature current to reduce the field flux caused by armature reaction in a DC motor.

Interpolation: Method for producing measuring increments which are smaller than a 4th of the scanning signal period.

Inverter: An electronic device that converts fixed frequency and fixed voltages to variable frequency and voltage. Enables the user to electrically adjust the speed of an AC motor. I 2 R Losses due to current flowing in a conductor caused by resistance (equals the current squared times the resistance).

All glossary contents are copyrighted and the property of their respective owners. See our copyright statement for more information.