ELT 115: Variable Frequency Drives and Electrical Raceways

Variable Frequency AC Drives   

 Segment 1- Variable Speed AC Drive Basics

1. Describe the function and operation of two common types of variable speed AC drives.
2. Describe the advantages and disadvantages of using an AC drive instead of a DC drive.
3. Describe the advantages of starting a motor with an AC drive instead of line starting.
4. Operate a motor using the program keypad of a variable frequency AC drive.

Segment 2- Two and Three-Wire Control

1. Describe the external control capabilities of a variable frequency AC drive.
2. Program and connect a variable frequency AC drive for three-wire control.
3. Operate a three-wire control circuit using a variable frequency AC drive.
4. Program and operate a two-wire control circuit using a variable frequency drive.

  Segment 3- Jogging Control

1. Describe how motor jogging Is accomplished with a variable frequency AC drive.
2. Program, connect and operate a variable frequency AC drive for motor jogging.

Variable Frequency AC Drives - Speed and Torque Control

 Segment 1 – Basic Speed Control

1. Describe how frequency affects the speed on an AC induction motor.
2. Describe the output of a variable frequency drive.
3. Define reflected wave voltage and describe its effect on an AC induction motor.
4. Describe three steps that can be taken to reduce the effects of reflected wave voltage.
5. Control motor speed using the keypad of a variable frequency AC drive.
6. Connect and operate a circuit to control motor speed using a variable frequency AC drive.

Segment 2 – Advanced Speed Control

1. Describe how to program a variable frequency AC drive for multiple speed selections.
2. Describe how to program a variable frequency AC drive to skip frequencies.
3. Program and operate a variable frequency AC drive using preset speeds.
4. Describe how to program a variable frequency AC drive to drive a motor above its base speed.
5. Program and operate a variable frequency AC drive to drive a motor above Its base speed.

Segment 3 – Torque Control

1. Define volts per hertz ratio.
2. Explain how the volts per hertz ratio affects the torque capabilities of a motor.
3. Calculate volts per hertz ratio.
4. Program and operate a variable frequency AC drive to provide low speed boost.

Variable Frequency AC Drives -Acceleration/Deceleration and Braking

  Segment 1 – Ramping

1. Define ramping and explain its importance.
2. Explain how ramping is accomplished using a variable frequency AC drive.
3. Program and operate a variable frequency AC drive to ramp a motor to its rated speed.
4. Program and operate a variable frequency AC drive to ramp a motor to a stop.

Segment 2 – Special Acceleration Methods

1. Describe how a variable frequency AC drive can accelerate a motor past its rated speed.
2. Program and operate a variable frequency AC drive to ramp an AC motor past its rated speed.
3. Describe S-Curve acceleration and explain How It Is used.
4. Program and operate a variable frequency AC drive to provide S-Curve acceleration.

Segment 3 – Braking

1. Describe DC injection braking using a variable frequency AC drive and give an application.
2. Program and operate a variable frequency AC drive to provide DC injection braking to a motor.

Variable Frequency AC Drive - Fault Diagnostics and Troubleshooting

Segment 1 – Fault Detection

1. Describe how a variable frequency AC drive detects faults.
2. Describe six common faults that can be detected by a variable frequency drive.
3. Determine faults based on the fault display of a variable frequency AC drive.

Segment 2 – Troubleshooting

1. Describe how to troubleshoot a circuit that includes a variable frequency AC drive.
2. Troubleshoot the parameter settings of a variable frequency AC drive.
3. Troubleshoot a circuit that includes a variable frequency AC drive.

Segment 3 – Clearing Faults

1. Describe how to program a variable frequency AC drive to clear a fault.
2. Program a variable frequency AC drive to automatically reset a fault.
3. Manually clear a fault on a variable frequency drive.

Electrical Raceways

 Segment 1 – Conduit Basics

1. Describe the function of a wiring system.
2. Describe the function of the four basic parts of a wiring system.
3. Describe the function of conduit and list five types.
4. Conduit identification and familiarization.

Segment 2 – EMT Conduit Cutoff and Preparation

1. Describe three methods by which conduit is cut.
2. Describe the construction and operation of a hacksaw.
3. Change a blade on a hacksaw.
4. Describe the function of a pipe vise and give three types.
5. Describe the construction and operation of a bench vise with pipe jaws.
6. Describe six safety rules to follow when operating the bench vise.
7. Use a bench vise to hold conduit.
8. Cut EMT conduit to length using a Hacksaw.
9. Describe the function of deburring conduit and give four tools that can be used.
10. Deburr conduit.

Segment 3 – Conduit Bodies and Boxes

1. Describe the function of an electrical box and give an application.
2. Describe the function of a conduit body and give an application.

Segment 4 – Conduit Fittings

1. Describe the function of a conduit fitting.
2. Describe the function and operation of three types of connectors.
3. Calculate conduit length given an application.
4. Connect EMT between two boxes.
5. Describe the function of a coupling.
6. Couple EMT conduit.
7. Describe the function of a conduit strap and list three types.

Basic Conduit Bending

  Segment 1 – Conduit Benders

1. Describe the function of conduit bending and list three basic types of bends.
2. Describe the function of a conduit bender and two methods that are used to bend conduit.
3. Describe four types of benders used with metallic conduit.
4. Describe the construction and operation of a hand bender.
5. Identify the components of a hand bender.

Segment 2 – Basic Conduit Bending

1. Define the components of a 90° bend.
2. Describe bender take-up and its importance in making a 90° bend.
3. Describe the five steps used to determine bender take-up.
4. Determine the take-up of a hand bender.
5. Describe the five steps to lay out accurate leg lengths and stub lengths.
6. Lay Out and bend EMT with proper leg length and stub-up.

Segment 3 – Offset Bends

1. Describe the components of an offset bend.
2. Describe the four steps used to determine and locate the bend centers of an offset bend.
3. Determine and locate the bend centers of an offset bend.
4. Bend an offset in EMT conduit.
5. Construct a raceway of EMT conduit.

Advanced Raceways

Segment 1 – IMC and Rigid Conduit Cutoff 

1. Describe the similarities and differences between intermediate metallic and rigid conduit.
2. Describe three tools used to cut intermediate metallic and rigid conduit.
3. Cut intermediate metallic conduit.

Segment 2– IMC Conduit Bending 

1. Describe two tools used to bend IMC and rigid conduit.
2. Describe the construction and operation of a mechanical bender.
3. Identify the components of a mechanical bender.
4. Change the shoe of a mechanical bender.
5. Bend IMC with a mechanical bender.

Segment 3 – IMC Conduit Assembly 

1. Describe the method used to thread IMC and rigid conduit.
2. Describe the connectors and couplings used with IMC and rigid conduit.
3. Thread IMC conduit.
4. Connect and couple IMC given an application.

Segment 4 – Flexible Conduit

1. Describe how flexible metal conduit is cut.
2. Cut flexible metal conduit.
3. Describe the connectors used with flexible metal conduit.
4. Connect flexible metal conduit.

Conductors, Disconnects, and Overcurrent Protection

Segment 1 – Conductors 

1. Describe the function of a conductor and list its two components.
2. Describe the factors that affect conductor selection.
3. Describe five common classifications of insulation and give an application of each
4. Define conductor ampacity and describe the physical characteristics that affect it
5. Describe how distance affects wire Selection.
6. Select wire size and type for an application.

Segment 2– Disconnects 

1. Describe the function of a disconnect and give an application.
2. Describe three commonly used types of disconnects and give an application of each.
3. Describe how to size a disconnect.
4. Select a disconnect for an application.

Segment 3 – Overcurrent Protection 

1. Describe the function of overcurrent protection and list two types.
2. Describe how to size circuit protection.
3. Select circuit protection for an application.

Conduit Sizing and Wire Pulling Techniques

Segment 1 – Raceway Specification and Selection 

1. Describe percentage of fill and its importance in raceway selection.
2. Describe two methods used to select raceway diameter.
3. Use NEC tables to select the proper size raceway for same size/type conductors.
4. Describe the seven steps used to determine conduit size when conductors are of different size and/or type.
5. Determine conduit size when conductors are of different size and/or types.

Segment 2– Conduit Body and Electrical Box Selection 

1. Describe why electrical codes limit the number of conductors in an electrical box.
2. Describe how to select the correct size electrical box.
3. Describe how conduit bodies are selected.
4. Determine electrical box size when conductors are the same size.
5. Determine electrical box size when conductors are of different sizes.

Segment 3 – Conductor Pulling

1. Describe three methods used to pull conductors.
2. Pull conductors using fish tape.

Segment 4 – Power Distribution System Installation

1. Describe the function of a bus bar and give an application.
2. Describe the function of a bus plug.
3. Connect a bus plug to a bus bar.
4. Design and install a wiring system given specifications.