Condition Sensing Switches and Controls

Catalogs > Industrial Controls Catalog > Condition Sensing Switches and Controls > Speed Sensing

Speed Sensing

Introduction Technical Data Ordering Information Product Selection Modifications and Accessories Standards Compliance and Certifications Approximate Dimensions
Product Overview


Click to enlarge - 808-14_1-1
Bulletin 808 with lockout solenoid and four-point flange mounting


Bulletin 808 Speed Switches


Click to enlarge - 808-14_1-2
Bulletin 808 Base Mounting with Cover Removed and Lockout Cover Sectioned to show Interior


Description

Bulletin 808 Speed Switches are pilot devices used for detecting speed or direction of rotation. They are commonly used in applications requiring forward plugging, motor sequencing, and anti-plugging circuitry and are an effective means of detecting broken belts or couplings. Allen-Bradley Bulletin 808 Speed Switches utilize magnetic coupling technology to increase product life and reliability, eliminating the possibility of failure due to mechanical and hydraulic couplings that can wear or leak over time. Bulletin 808 Speed Switches are supplied as standard with a sealed outboard bearing and an additional external seal. The external seal reduces the effects of contaminants and increases the life of the device. Bulletin 808 Speed Switches offer a variety of mounting arrangements and have been designed to allow for easy speed adjustments in the field. Speed switches are not designed to sense shaft speed below 15 RPM, and will not sense zero shaft speed. Low RPM sensing can be achieved by modifying the shaft speed ratio via gearing or pulley arrangements. Speed switches wired for plugging applications achieve zero speed by employing the millisecond decay of the electromagnetic fields of the reversing starter and motor.

Applications


Styles J and K — Low Speed Switches

Click to enlarge - 808-14_2-1
Type 1, 4 & 13


Style J


Style K


Styles M and R — High Speed Switches

Click to enlarge - 808-14_2-2
Type 7 & 9


Style M


Style R


Typical Industrial Applications

Plugging — Stops a motor quickly. A speed switch with normally open contacts is used in conjunction with a contactor or starter wired to reverse the field windings of a squirrel cage motor. In plugging applications, the device, when properly adjusted to given conditions, will provide the control circuit logic to apply reverse energy to the motor to reach zero speed. The motor, electrical power distribution, and machine must be designed to handle sudden stopping.

Application examples include:


Anti-Plugging — Allows a machine to coast until it reaches a safe speed. A speed switch with normally closed contacts is wired into a suitable circuit. When properly set, the device will not allow reversing or apply braking, by a designated method, until the machine has reached a safe speed.

Application examples include:


Speed Sensing — Detects approximate shaft speed. The device with normally open or normally closed contacts can be used, in an appropriate circuit, to sense the approximate speed of a rotating shaft.

Application examples include:


Direction of Rotation — Detects direction of shaft rotation. The device can be wired into a circuit to sense clockwise or counterclockwise shaft rotation. Normally open or normally closed contacts can be used depending upon the requirements of the circuit.

Application examples include: