AC Control Equipment

Lesson 1 - Motor Starters

Topics:

Motor controllers; Controller enclosures; Starters; Magnetic controls; Interlocks, Reversing and combination starters

Learning Objectives:

– Describe the difference between a manual starter and a magnetic starter.
– Explain the function of a shading coil in a magnetic starter.
– Explain the effects of low voltage on a controller.
– State the reason why holding-circuit interlocks are required on magnetic starters and contactors.

Lesson 2 - Switches and Controls

Topics:

Pushbuttons; Selector switches; Wall boxes; Contact blocks; Indicating lights; Circuit diagrams; Legend plates

Learning Objectives:

– Discuss the characteristics of industrial switches and controls.
– Identify the five most commonly used NEMA pushbutton stations.
– Demonstrate how to mount an oil-tight control station both vertically and horizontally.
– Explain the difference between standard and press-to-test indicating lights.
– Explain how a three-wire control circuit works.

Lesson 3 - Limit Switches

Topics:

Precision snapswitches; Limit switches; Mercury-tilt switches; Switch installation and failure

Learning Objectives:

– List the main parts of a precision snap-action limit switch.
– Describe the contact arrangement of a snapswitch.
– Describe the kinds of actuators used in limit switches.
– List the rules for the proper design and application of limit switch cams.
–  Explain how a mercury switch works.

Lesson 4 - Special Control Switches

Topics:

Reversing drum, foot, transfer, plugging, mechanical, magnetic plugging, pressure, temperature - and float switches

Learning Objectives:

– Explain how a drum switch works.
– Select the best switch for stopping a motor quickly.
– List the criteria for selecting a plugging switch.
– Identify different types of pressure switches.
– State the definition of pressure differential.

Lesson 5 - Timers and Counters

Topics:

Interval and reset timers; Time-delay relays; Repeat-cycle, pulse, and percentage timers;Impulse, electric, and revolution counters; Time totalizers

Learning Objectives:

– Explain how a reset timer works.
– Describe the different types of timers.
– Compare and contrast an electric counter and a time totalizer.
– Select the best control device for use where a machine cannot be controlled by time.
– Demonstrate how to set up a chart for a programed control circuit.

Lesson 6 - Control Relays

Topics:

Contact operation; Mountings, enclosures, terminals, and definitions; NEMA classes; Causes of failure

Learning Objectives:

– State the definition of a relay
– Explain the function of relay contacts.
– Select the best relay for use where large movement of the contacts or high contact force is required.– List the advantages of a reed relay.
– Tell why industrial relays usually have double-break contacts.

Lesson 7 - Equipment for Hazardous Locations

Topics:

Enclosures; Sources of ignition; Switchgear and industrial controls; Lighting; Motors and generators; Plugs and receptacles, Portable equipment; Conduit

Learning Objectives:

– List the requirements an enclosure must meet in order to be called explosionproof.
– List the characteristics of switchgear and industrial controls-in hazardous conditions.
– List three situations in hazardous locations that require the use of seals.
– List the three basic conditions that can cause fire or explosion.
– Demonstrate how to terminate armored cable that enters an explosionproof housing.

Lesson 8 - Special Motor Controls

Topics:

Synchronous motor control; Sequence-accelerating and decelerating relays; Transformer starters

Learning Objectives:

– Name the two relays required for automatic starting of a synchronous motor.
– Explain how an automatic sequence-accelerating relay works.
– Select the best starter for use where the highest possible starting torque per ampere of line current is required.– List the characteristics of different types of resistance starters.– Describe a Y-delta starter.

Lesson 9 - Motor Control Centers

Topics:

Features and advantages; MCC bus; NEMA standards; Enclosure construction; Wiring; Circuit protection; Installation

Learning Objectives:

– Define the term motor control center.
– Name the main advantages and disadvantages of back-to-back MCC construction.
– Explain how to install an MCC.
– Define a note, a caution, and a warning as each relates to MCC equipment.
– List the checks to conduct prior to releasing an MCC for plant operation.

Lesson 10 - Control Panel Wiring

Topics:

Enclosures; Terminal blocks; Wire identification; Connections; Connectors; Wire dressing

Learning Objectives:

– State the function of terminal blocks.
– Demonstrate how to make a terminal connection.
– Tell when to use different types of connectors.
– Describe the proper lacing of wires in a control panel.
– Explain when and how to use a wiring duct.