ECE 211 Lectures Page 1 Lecture 15 Motor Controls & Drives Tuesday, July 29, 2014 1:00 PM DC Motors and Control Circuits Types of DC Motors Shunt Motors Series Motors Compound Motors Permanent Magnet Motor (PM) Brushless DC Motors Steppers Example 1: 110V DC Motors and Controls Example 2: PM Motor and Control Example 3: PM Motor with Power Transistor Control Example 4: PM Motor with Half-Wave Rectifier Power Source Example 5: PM Motor with Full-Wave Rectifier Power Source AC Motors and Control Circuits Example 6: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Magnetic Switch On/Off Control Example 7: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Relay and Solid State Relay On/Off Control Example 8: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Computer & Solid State Relay On/Off Control Examples 9 & 10: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Demo Example 11: Light Activated AC Motor Control Example 12: Three-Phase Motor On-Off Control Motor Principle E = KΦN V t = E + I a R a I a = (V t E)/R a Torque Development T = F r = K f I a Power Relationships o V t I a = E*I a + I a2 R a o Power output in horsepower = (2π NT) /33,000 = NT/5252 N = speed of motor, RPM T = torque of motor pulley, pound-ft o Power output in Watts = (2π NT) /60 = NT/9.55 N = speed of motor, RPM T = torque of motor pulley, Newton-meters Interpole Motor speed regulation Motor Staring Motor equations: o V t = E + I a R a o E = Kf n Motor starting requirements o Limiting excessive starting current Add series resistance during starting period, or Reduce line voltage during starting period o High starting torque Motor Speed Control N = (V t - I a R a )/(KΦ) o Field flux control (field weakening) o Armature-circuit resistance control Terminal voltage control
ECE 211 Lectures Page 2 N = (V t - I a R a )/(KΦ) o Field flux control (field weakening) o Armature-circuit resistance control o Terminal voltage control Motor Speed Regulation Magnetic Contacts, Push Buttons Ladder Diagrams and Motor Control Dynamic Breaking Power supply for DC motors o Rectifier Drive Systems Example 1: DC Motor Control Series Motors Shunt Motors Speed Control Speed N = (Ea - I*R)/(K*Φ) Compound Motors Example 2: PM Motors and Control PM Motor (Permanent magnet) generate a constant field flux
ECE 211 Lectures Page 3 R a = armature resistance V a = armature terminal voltage I a = armature-current E a = Armature emf, speed voltage ω m rad/sec K m : V/(rad/sec) is known as torque constant which is a function of motor geometry and magnet properties. T mech = E a I a /ω m = K m I a Example 3: PM Motors and Power Transistor Control
Example 4: PM Motor with Half-Wave Rectifier Power Source Example 5: PM Motor with Full-Wave Rectifier Power Source Example 6: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Magnetic Switch On/Off Control Major components ECE 211 Lectures Page 4
ECE 211 Lectures Page 5 Example 6: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Magnetic Switch On/Off Control Major components Operation Procedure/Method 1. Connect the motor circuit and control circuit 2. Start the Motor 2-1. Push the "START" button *CR relay is energized from the path: L1-STOP-START-CR coil-l2 *All CR contacts (CR1 to CR4) are closed, 1Φ motor start to run (the two windings: main winding; centrifugal sw & auxiliary winding) * The motor receive the AC 120 V power form the following path: L1 - CR2 contact - Motor - CR3 contact - L2 2-2. Release the "START" button * CR1 remains close (memorizing the Push On action), CR relay is now energized through the path: L1-STOP- CR1-CR Coil-L2 *When the motor reaches a certain speed, the centrifugal sw is open, and the main winding remains in the circuit for normal running 3. Stop the Motor 3-1. Push the "STOP" button 3-2. CR coil is de-energized 3-3. All CR contacts are open 3-4. The motor is disconnected from L1, L2 power source, motor stop Example 7: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Relay and Solid State Relay On/Off Control Major Component Push buttons: Start (ON), Stop (Off) 1 x Control relay with 2 normally open (NO) contacts 1 x Solid State Relay (10 to 20A) 1Φ Split-phase IM AC 120 V source, 12V DC source
ECE 211 Lectures Page 6 Operation Procedure 1. Connect the motor circuit and control circuit 2. Start the Motor 2-1. Push the "START" button *CR relay is energized from the path: V+ =>STOP =>START => CR coil => V- *All CR contacts (CR1 to CR2) are closed * CR1 serves as a 1-bit (on/off) memory to hold the ON state * CR2 passes the 12V DC to the DC input of the SSR, and turns the LED on * LED light on, in turn, fires the gate triggering circuit, then turn-on the TRIAC (a power electronic device) * Finally the AC 120V passes the AC current through the TRIAC to run the 1Φ motor *When the motor reaches a certain speed, the centrifugal sw is open, and the main winding remains in the circuit for normal running 3. Stop the Motor 3-1. Push the "STOP" button 3-2. CR coil is de-energized 3-3. All CR contacts are open 3-4. The motor is disconnected from the power source, motor stop Example 8: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Computer & Solid State Relay On/Off Control Major Component Push buttons: Start (ON), Stop (Off) 1 x Solid State Relay (10 to 20A) 1 x Industrial Microcontroller 1Φ Split-phase IM AC 120 V source, 12V DC source
ECE 211 Lectures Page 7 Operation Procedure A. Design and code a simple microcontroller program for On/Off control B. Download the control program to the Microcontroller C. Execute the Motor On/Off Control Program a. Lookup DI (digital input) input for SW On/Off state b. Send the On or Off SW state to DO (digital output) port and hold the state c. SSR input receives "High" or "1" state, turns on the SSR's LED d. SSR's LED light on, in turn, fires the gate triggering circuit, then turn-on the TRIAC (a power electronic device) e. Finally the AC 120V passes the AC current through the TRIAC to run the 1Φ motor *When the motor reaches a certain speed, the centrifugal sw is open, and the main winding remains in the circuit for normal running D. Stop the Motor a. Turn the SW Off b. Control program lookup DI input for SW in Off state c. Microcontroller sends "0" or "Low" signal to SSR's LED, turn off LED, turn off TRIAC d. The motor is disconnected from the power source, motor stop Examples 9 and 10: 1Φ 1/4 HP, 115V, Split-Phase Induction Motor - Demo See Demo Examples 11: Light Activated Motor Control
ECE 211 Lectures Page 8 Example 12: Three-Phase Motor On-Off Control Operation Procedure/Method 1. Connect the motor circuit and control circuit 2. Start the Motor 2-1. Push the "START" button *Magnetic Switch's coil is energized from the path: L1-STOP-START-CR coil-l2 *All MS contacts (MS1 to MS4) are closed, 3Φ motor start to run *The 3Φ motor receive the AC 220 V power form the following path: L1/L2/L3 <=> MS2/MS3/MS4 contacts <=> Motor 2-2. Release the "START" button * MS1 remains close (memorizing the Push On action), MS coil is now energized through the path: L1-STOP- MS1-MS Coil-L2 3. Stop the Motor 3-1. Push the "STOP" button 3-2. MS coil is de-energized 3-3. All MS contacts are open 3-4. The motor is disconnected from L1, L2, L3 power source, motor stop