Consulting-Specifying Engineer - July 2008 - (Page 45) T M s 2nd quadrant – braking while lifting the load T M s 3rd quadrant – lowering the load s s + Speed s T M Electromagnetically induced circulating current Frame Stator iron 1st quadrant – raising the load - Torque 0 T + Torque T M 4th quadrant – braking while lowering the load Nondrive-end bearing Rotor Stator winding Shaft - Torque T Airgap Driveend bearing - Speed s Figure 3: Applications that require operation in both directions, plus positive torque for negative direction and vice versa, operate in all four quadrants of the speed-torque plane. 3-phase ac to motor Stray magnetic flux E Width modulated pulses Figure 6: In all motors there is a small electromagnetically induced voltage in the motor shaft in the axial direction. This is caused by the leakage of magnetic flux linking the rotor and the shaft outside the airgap. Edc CWF CRF Stator iron CWF Stator winding Shaft CBDE 0º 180º 360º wt CBNDE Nondrive-end bearing CWR CWR Rotor CWR Airgap CRF CWF CRF CWR CRF CWF Average voltage Driveend bearing Figure 4: Typical line-to-line output voltage for a pulse-widthmodulated variable frequency drive. Voltage doubling effect due to reflection High freq. ringing due to stray capacitance E-dc link voltage CWR V CWF CBNDE VB CRF CBDE Frame Stator winding Rotor Motor voltage 1 pulse wt V = Voltage impressed upon the windings (PWM pulses) VB = Voltage appearing across the bearings CWF = Winding-to-frame capacitance CWR = Winding-to-rotor capacitance CRF = Rotor-to-frame capacitance CBDE = Capacitance across drive-end bearing CBNDE = Capacitance across non-drive-end bearing Figure 5: Voltage at the motor terminals due to pulse-widthmodulated variable frequency drive shows high frequency ringing and doubling due to reflection. Figure 7: With electrostatic-induced voltage, stray capacitances, which normally have negligible effect, come into play when highfrequency pulses are impressed upon the winding. Source all figures: Syed Peeran Consulting-Specifying Engineer • JULY 2008 45
Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - July 2008 Consulting-Specifying Engineer - July 2008 Contents Viewpoint Letters News M/E Roundtable 40 Under 40 Using Demand-Based Reset Strategies VFDs and Motors: Making the Right Match Grounding and Bonding Practices for Hazardous Areas Codes & Standards Case Study New Products Equipment Lifecycles Advertiser Index Green Space Consulting-Specifying Engineer - July 2008 Consulting-Specifying Engineer - July 2008 - Consulting-Specifying Engineer - July 2008 (Page Cover1) Consulting-Specifying Engineer - July 2008 - Consulting-Specifying Engineer - July 2008 (Page Cover2) Consulting-Specifying Engineer - July 2008 - Consulting-Specifying Engineer - July 2008 (Page 1) Consulting-Specifying Engineer - July 2008 - Consulting-Specifying Engineer - July 2008 (Page 2) Consulting-Specifying Engineer - July 2008 - Contents (Page 3) Consulting-Specifying Engineer - July 2008 - Contents (Page 4) Consulting-Specifying Engineer - July 2008 - Contents (Page 5) Consulting-Specifying Engineer - July 2008 - Contents (Page 6) Consulting-Specifying Engineer - July 2008 - Viewpoint (Page 7) Consulting-Specifying Engineer - July 2008 - Letters (Page 8) Consulting-Specifying Engineer - July 2008 - Letters (Page 9) Consulting-Specifying Engineer - July 2008 - News (Page 10) Consulting-Specifying Engineer - July 2008 - News (Page 11) Consulting-Specifying Engineer - July 2008 - M/E Roundtable (Page 12) Consulting-Specifying Engineer - July 2008 - M/E Roundtable (Page 13) Consulting-Specifying Engineer - July 2008 - M/E Roundtable (Page 14) Consulting-Specifying Engineer - July 2008 - M/E Roundtable (Page 15) Consulting-Specifying Engineer - July 2008 - M/E Roundtable (Page 16) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 17) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 18) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 19) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 20) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 21) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 22) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 23) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 24) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 25) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 26) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 27) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 28) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 29) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 30) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 31) Consulting-Specifying Engineer - July 2008 - 40 Under 40 (Page 32) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 33) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 34) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 35) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 36) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 37) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 38) Consulting-Specifying Engineer - July 2008 - Using Demand-Based Reset Strategies (Page 39) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 40) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 41) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 42) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 43) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 44) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 45) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 46) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 47) Consulting-Specifying Engineer - July 2008 - VFDs and Motors: Making the Right Match (Page 48) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 49) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 50) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 51) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 52) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 52A) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 52B) Consulting-Specifying Engineer - July 2008 - Grounding and Bonding Practices for Hazardous Areas (Page 53) Consulting-Specifying Engineer - July 2008 - Codes & Standards (Page 54) Consulting-Specifying Engineer - July 2008 - Codes & Standards (Page 55) Consulting-Specifying Engineer - July 2008 - Case Study (Page 56) Consulting-Specifying Engineer - July 2008 - Case Study (Page 57) Consulting-Specifying Engineer - July 2008 - New Products (Page 58) Consulting-Specifying Engineer - July 2008 - New Products (Page 59) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 60) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 61) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 62) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 63) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 64) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 65) Consulting-Specifying Engineer - July 2008 - Equipment Lifecycles (Page 66) Consulting-Specifying Engineer - July 2008 - Advertiser Index (Page 67) Consulting-Specifying Engineer - July 2008 - Green Space (Page 68) Consulting-Specifying Engineer - July 2008 - Green Space (Page Cover3) Consulting-Specifying Engineer - July 2008 - Green Space (Page Cover4)
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