Maricopa Community Colleges  ELC218   19962-99999 
Official Course Description: MCCCD Approval: 11/28/95
ELC218 19962-99999 LEC 3 Credit(s) 3 Period(s)
Variable Frequency Drives
Principles and operation of frequency controlled AC(Alternating current) motor drives, including current source inverters (CSI), variable voltage inverters (VVI) and pulse width modulated inverters (PWM). Heating, ventilation and air conditioning (HVAC) applications along with energy savings, motor pump sizing and torque load calculations. Prerequisites: Permission of instructor.
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MCCCD Official Course Competencies:
 
ELC218   19962-99999 Variable Frequency Drives
1. Describe the construction and operation of AC induction motors. (I)
2. Explain the effect of frequency of the speed of an AC motor. (II)
3. Explain the effect of frequency of the torque output of an AC motor. (III)
4. Describe the construction and operation of current source inverters (CSI). (IV)
5. Describe the construction and operation of variable voltage inverters. (V)
6. Describe the construction and operation of pulse width modulated inverters. (VI)
7. Determine horse power requirements for various sized pump applications. (VII)
8. Describe an open loop speed control system. (VIII)
9. Describe slip compensation control systems. (IX)
10. Describe closed loop control systems. (X)
11. Determine energy savings with variable frequency drives versus standard drives. (XI)
12. Describe adjustments and classes of variable frequency drives. (XII)
13. Explain the application of variable speed drives to heating, ventilating and air conditioning systems. (XIII)
14. Explain the application of variable speed drives to industrial systems. (XIV)
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MCCCD Official Course Outline:
 
ELC218   19962-99999 Variable Frequency Drives
    I. AC induction motors
        A. Basic construction
        B. Induction characteristics from field to rotor
        C. Rotating magnetic filed instator
      II. Frequency and speed
          A. Slip speed
          B. Number of pole pairs
          C. Frequency variance
        III. Frequency and torque
            A. Air gap flux density
            B. Impedance variance
            C. Voltage variation
            D. Frequency/voltage relationship ELC218Effective Term:
          IV. Current source inverters
              A. Description
              B. Operational characteristics
              C. Advantages/disadvantages
            V. Variable voltage inverters
                A. Description
                B. Operational characteristics
                C. Advantages/disadvantages
              VI. Pulse width modulated inverters
                  A. Description
                  B. Operational characteristics
                  C. Advantages/disadvantages
                VII. Horse power requirements
                    A. Duty cycle
                    B. Flow formula
                    C. Weighted horsepower
                  VIII. Open loop speed control
                      A. Synchronous motor applications
                      B. Nema B motor
                      C. Slip characteristics
                      D. Efficiency
                    IX. Slip compensation control
                        A. Drive output transducers
                        B. Voltage/frequency change
                        C. Synchronous and multi-motor applications
                        D. Efficiency
                      X. Closed loop speed control
                          A. Feed back devices
                          B. Error signals
                          C. Set point frequency
                        XI. Energy savings
                            A. Outlet damper versus variable speed
                            B. Pressure requirements
                            C. Throttle valves
                            D. Mechanical variable speed
                            E. Cycling system
                          XII. Adjustments/classes
                              A. General purpose drive
                              B. Industrial rated drives
                              C. Intelligent interface drives ELC218Effective Term:
                            XIII. Applications - heating, ventilation, and air conditioning
                                A. Air handling
                                B. Refrigerant compressors
                                C. Heating systems
                              XIV. Applications - industrial
                                  A. Gear driven machinery
                                  B. Belt driver machinery
                                  C. Pump flow rates
                                  D. Variable speed mills
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