hubbell industrial controls, inc.

Applications

General Uses

Plugging

A common use for a speed responsive

switch is in plugging an electric motor.

(Rapidly stopping an electrical motor

by applying reverse power through a

reversing contactor). Plugging in-

creases the number of machine opera-

tions per unit of time by reducing the

stopping time of the motor and the

machine it drives. When used for plug-

ging, a speed responsive switch acts

with a magnetic control to allow re-

verse power to be applied to a rotat-

ing motor. The power is automatically

removed by the switch when the

motor approaches zero speed, to pre-

vent undesirable reversing.

Anti-Plugging

Anti-plugging is used to prevent the

application of reverse power to a mo-

tor operating above a preset speed.

One area is in equipment with high

inertia loads, where plugging from full

speed in either direction could cause

motor or equipment damage. A speed

responsive switch used for anti-plug-

ging will not allow a motor to be

plugged until it has decelerated to a

predetermined safe speed.

Material Handling Interlocking

& Sequencing

Another useful application area for

speed responsive switches is in bulk

material handling systems. The illus-

tration on the next page shows the vari-

ous functions of speed responsive

switches:

Switch “A” senses rotary

feeder shaft motion. Slowing

or stopping of the feeder shaft

indicates a malfunction such

as a jammed feeder or a

plugged outlet. The speed re-

sponsive switch is set to open

the drive motor circuit at some

feeder shaft speed below nor-

mal.

A speed response switch indicates

motion, speed and assists in the control

of rotating machinery.

If you need to know whether or not a

shaft is rotating, running at an accept-

able speed or which way it is rotating,

consider using a speed responsive

switch. Such a device can remotely in-

dicate shaft motion and direction and ac-

tuate control circuits at adjustable se-

lected speeds. Numerous safety, se-

quencing, and interlocking control func-

tions can be performed automatically

with these versatile units.

Many automatic machine control ac-

tions are based on rotary shaft speed.

Often a particular shaft speed and/or

direction of rotation is important. For

example:

1. In certain portions of a machine

cycle, motion of any kind is un-

wanted.

2. Rotation in the wrong direction

must be prevented.

3. A particular shaft speed marks

the beginning of a dangerous

overspeed or underspeed con-

dition.

4. Sequential operations must

take place at definite rotary

speeds.

Where sensing and/or control of rotary

speed is required, speed responsive

switches are often the best choice.

These rugged reliable components

open or close electrical contacts at pre-

set adjustable rotary speeds, in one or

both directions of rotation. The contact

operations can effect a variety of auto-

matic indicating and control actions. A

number of proved industrial applications

for these units are listed below:

Industrial Uses

Electric Motors

• Indicate rotation and/or direc-

tion of rotation.

• Plugging and anti-plugging or

preventing overspeed.

• Provide speed governing and

adjustable speed action for

motors.

Materials Handling Equipment

• Indicate slowdown or stoppage

of rotating shafts on rotary feed-

ers, conveyors, bucket eleva-

tors, and other material handling

equipment.

• Operate emergency braking

equipment on cranes, hoists,

etc.

Production Equipment

• Disconnect or stop drive if

speed drops below normal due

to a machine jam or other type

of overload.

• Energize electromagnetic

clutches and brakes at preset

speeds.

• Indicate number of equipment

starts and stops (with counter)

• Interlock equipment actions.

• Prevent accelerations, slow-

downs and reversals of mixers

and centrifuges.

• Provide overspeed and under-

speed protection for machines

and processes.

• Shift gears automatically (ma-

chine tool transmissions).

• Remotely indicate faulty opera-

tions of any rotating parts.