IMD 3020 - Electrical Motor Control Systems

• Explain electro-magnetism
• Explain electro-magnetic induction
• Explain the volts-per-turn principle
• Explain mutual-induction
• Explain self-induction
• Explain a counter electro-motive force (CEMF)
• Explain how inductors:
• Oppose a change in current
• Cause a phase-shift between a voltage and current
• Identify the parts of an induction motor
• Explain each part of an induction motor
• Explain electro-magnetic induction to the rotor of an induction motor
• Explain the difference between conducting and inducing electrical energy to the rotating member of an electric motor
• Explain what power factor is
• Define the electrical/mechanical terminology associated with power factor
• Explain how induction motors cause a power factor problem
• Explain the current draw and torque-speed curve operating characteristics of induction motors
• Explain the law of charges
• Relate the forces of electro-static charges to the forces of magnetic fields
• Explain two advantages of using electro-magnets in induction motors
• Explain the physical relationships of three-phase induction motor stator coils
• Explain how the stator coils of a three-phase induction motor, with three-phase AC power, creates a rotating magnetic field in the motor stator
• Explain synchronous speed and how to calculate it
• Explain rotor slip and how to calculate it expressed as a percentage
• Explain why rotor slip is necessary for an induction motor to produce turning torque
• Explain why locked rotor current is the maximum current an induction motor can draw from the power supply
• Explain why the rotor of an induction motor cannot produce turning torque if it is turning at synchronous speed
• Explain the locked rotor power losses of induction motors
• Identify the advantages and disadvantages of single-phase induction motors over three-phase induction motors
• Identify the parts of a single-phase induction motor
• Explain the function and operation of the auxiliary windings in single-phase motors
• Explain the function and operation of the centrifugal switch in single-phase induction motors
• Name, identify the wiring diagram for, and discuss the operating characteristics of, the four most common split-phase induction motors
• Explain the differences between motor starting capacitors and motor running capacitors
• Explain a safe method for discharging capacitors in an electrical circuit
• Explain the difference between motor nameplate voltage ratings of motors, and voltage of electrical supply distribution systems
• Explain how to reverse a single-phase induction motor
• Explain a single-phase single-voltage, reversible motor connection
• Explain a single-phase dual-voltage, reversible motor connection
• Explain how to reverse a three-phase induction motor
• Explain the nine-lead WYE connected low-voltage motor connection
• Explain the nine-lead WYE connected high-voltage motor connection
• Explain the nine-lead Delta connected low-voltage motor connection
• Explain the nine-lead Delta connected high-voltage motor connection
• Explain how the stator coil ends are numbered for both WYE and Delta configurations
• Explain the use of a three-phase rotation tester
• Explain the purpose of motor nameplate information
• Identify the two common motor standards for electricians
• Explain common motor nameplate ratings
• Understand the terminology associated with magnetic relays and contactors
• List, identify, and explain the purpose and function of component parts of relays and contactors
• Understand the function and operating characteristics of the two separate electrical circuits present on each relay and contactor; the control and power circuits
• Explain pull-in and drop-out current
• Explain contact configurations and pin-out information
• Identify and explain the features of ice-cube relays
• Explain differences between relays and contactors that make them more suited for their different applications
• Explain purpose of arc chutes
• Identify contactor rating differences between NEMA and IEC
• Explain versatility of general purpose contactors and the functionality of definite purpose contactors
• Explain the purpose and need for an overload unit in an electric motor starter circuit
• Identify where in the motor control circuit the overload unit is found
• Explain the term “inverse time delay trip”
• Explain how the overload unit detects an overload condition from the motor load current, and opens the overload unit contacts
• Explain the two motor starter circuits found on the overload unit: the control and power circuits, and the purposes of both
• Identify the motor circuit components that are sized from the nameplate current
• Select an overload heater from a table, given the actual motor nameplate current
• Discuss the differences between the three most common types of overload units
• Explain how the magnetic contactor and overload units function together to create a magnetic motor starter
• Identify the functional parts of a motor starter
• Discuss the differences between magnetic and manual motor starters
• Discuss some of the configurations in which motor starters are found
• Explain the difference between overcurrent and overload
• Explain the electrical interconnection of the power circuit between the contactor unit and the overload unit
• Explain the electrical interconnection and function of the control circuit between the contractor unit and the overload unit
• Identify magnetic motor starter components
• Explain the difference between ladder diagrams and wiring diagrams
• Explain the placement and purpose for each point of reference documentation used on basic ladder diagrams
• Draw and document basic motor control circuit ladder diagrams
• Distinguish between motor control circuit input, or control’ and output, or load components
• Identify basic symbol contact switching methodologies and configurations
• Explain the Boolean Logic AND and OR contact configurations for motor control circuits
• Explain what two-wire motor control is
• Explain no-voltage and low-voltage drop-out protection
• Explain differential pilot devices
• Explain the operation of a Hands-Off-Automatic (HOA) circuit
• Explain what three-wire motor control is
• Explain the function of momentary contact control devices
• Explain the holding circuit
• Explain the operation of a three-wire motor control circuit
• Explain the terms inhibit and enable in reference to control circuit contacts
• Explain no-voltage and low-voltage drop-out protection
• Follow common motor control circuit schemes
• Describe the function and use of a VFD
• Describe soft start, as opposed to across the line full-voltage starting
• Discuss additional motor protection features of VFDs
• Discuss the types of electric motors suitable for use with VFDs
• Explain Pulse Width Modulation (PWM)
• Explain VFD modes of operation (constant torque, constant horsepower, and variable torque)
• Explain the quadrants of motor operation
• Explain re-generation
• Understand basic power and control circuit wiring for VFDs
• Understand basic operating parameters of VFDs
• Describe the use of default operating parameters
• Explain what a user defined input or output is
• Describe the digital input and relay output sections of a VFD
• Draw a control circuit on the terminal block from the user manual documentation
• Describe what commissioning a VFD entails