Terminology Pertaining To Electric Machinery

Bandwidth: Generally, this is the frequency range of a system input over which the system will respond satisfactorily to a command.

Base Speed: Base speed is the manufacturer's nameplate rating where the motor will develop rated HP at rated load and voltage. With DC drives, it is commonly the point where full armature voltage is applied with full rated field excitation. With AC systems, it is commonly the point where 60 Hz is applied to the induction motor.

Bases - Slide Rails: A two piece mounting system for motors which enable the motor to be mounted and leveled to the needed heights.

Bases - Sole Plates: A one piece mounting system for motors which enable the motor to be raised and lowered to the required height.

Bearing (Ball): A "ball" shaped component that is used to reduce friction and wear while supporting rotating elements. For a motor, this type of bearing provides a relatively rigid support for the output shaft.

Bearing Life: The expected endurance of motor bearings under specified load conditions. Bearing life is normally stated in terms of hours or years. Commonly referred to in motor specifications as B10 life or L10 life; both are used interchangeably.

Bearing (Roller): A special bearing system with cylindrical rollers capable of handling belted load applications that are too large for standard ball bearings.

Bipolar Transistor: Ordinary NPN or PNP transistor with emitter, base and collector are called bipolar since they operate through the collector are called bipolar since they operate through the flow of both holes and elections. Unipolar devices, such as FET transistors, operate through the flow of minority carries only, i.e. election flow.

Braking: Braking provides a means of stopping an AC or DC motor and can be accomplished in several ways:

Dynamic Braking (DC Drives) - Slows the motor by applying a resistive load across the armature leads after disconnection from the DC supply. This must be done while the motor field is energized. The motor then acts as a generator until the energy of the rotating armature is dissipated. This is not a holding brake.

Dynamic Braking (AC Drives) - Since AC motors do not have separate field excitation, dynamic braking is accomplished by continuing to excite the motor from the drive. This causes a regenerative current to the drive's DC intermediate bus circuit. The dynamic brake resistors are then placed across the DC bus to dissipate the power returned. The brake resistor is usually switched by a transistor or other power switch controlled by the drive.

Regenerative Braking - This is similar to dynamic braking, but it is accomplished electronically. The generated power is returned to the line through the power converter. It may also be just dissipated as losses in the converter (within its limitations).

Motor Mounted or Separately Mounted Brake - This is a positive action, mechanical, friction device. Normal configuration is such that when the power is removed, the brake is set. This can be used as a holding brake. (Note: A separately mounted brake is one which is located on some part of the mechanical drive train other than the motor..)

Braking Torque: The torque required to bring a motor down from running speed to a standstill. The term is also used to describe the torque developed by a motor during dynamic braking conditions.

Breakaway Torque: The torque required to start a machine from standstill.

Breakdown Torque: The maximum torque which a motor will develop with rated voltage applied at rated frequency, without an abrupt drop in speed.

Bridge Rectifier: A full wave rectifier that conducts current in only one direction of the input current. AC applied to the input results in approximate DC at the output.

Bridge Rectifier (Diode, SCR): A diode bridge rectifier is a non-controlled full wave rectifier that produces a constant, rectifier DC voltage. An SCR bridge rectifier is a full wave rectifier with an output that can be controlled by switching on the gate control element.

Brush: A brush is a conductor, usually composed of some element of carbon, serving to maintain an electrical connection between stationary and moving parts of a machine (commutator of a DC motor). The brush is mounted in a springloaded holder and positioned tangent to the commutator segments against which it "brushes." Pairs of brushes are equally spaced around the circumference of the commutator.

Buss Connections: An option on titan conduit boxes. Used to add up to three standoff insulators.

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