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mechatronics Flashcards

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1
Q

What is a three-phase power supply?

A

A three-phase power supply consists of three alternating currents (phases), each 120 degrees out of phase with one another.

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2
Q

What are the main parts of a three-phase motor?

A

The main parts are the stator (stationary part) and the rotor (rotating part).

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3
Q

How does the stator create movement in a three-phase motor?

A

The stator’s three sets of coils generate a rotating magnetic field when powered by three-phase current.

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4
Q

How does the rotor move in a three-phase motor?

A

The rotating magnetic field induces current in the rotor, creating a magnetic field that interacts with the stator’s field, causing the rotor to spin.

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5
Q

What is an induction motor?

A

An induction motor is an electric motor where the rotor is induced by the stator’s rotating magnetic field, without direct electrical connection to the power supply.

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6
Q

How does an induction motor generate torque?

A

The stator creates a rotating magnetic field, which induces a current in the rotor. The interaction between the rotor’s magnetic field and the stator’s field generates torque, causing the rotor to turn.

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7
Q

What is the working principle of an induction motor?

A

An induction motor works on the principle of electromagnetic induction, where a rotating magnetic field (RMF) in the stator induces current in the rotor, producing torque.

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8
Q

What is slip in an induction motor?

A

Slip is the difference between the synchronous speed (stator field speed) and rotor speed.

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9
Q

What are the two main types of induction motors?

A

Squirrel Cage Induction Motor – Simple, robust, low maintenance.

Slip Ring (Wound Rotor) Induction Motor – External resistors allow control of starting torque/speed.

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10
Q

What are key advantages and disadvantages of induction motors?

A

Advantages: Rugged, low cost, minimal maintenance, no brushes.
✖ Disadvantages: Speed control is complex, lower efficiency at light loads, high starting current.

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11
Q

What is a synchronous motor?

A

A synchronous motor is an AC motor that runs at a constant speed (synchronous speed) determined by the supply frequency and the number of poles. The rotor rotates in sync with the stator’s magnetic field.

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12
Q

What are the main characteristics of synchronous motors?

A

Runs at constant speed (no slip).
Requires DC excitation for the rotor (in wound rotor types).
Can operate at leading, lagging, or unity power factor.
Used for power factor correction.

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12
Q

Where are synchronous motors commonly used?

A

Power factor correction (synchronous condensers).

High-precision industrial drives (e.g., clocks, robotics).

Large compressors, pumps, and generators.

Constant-speed applications requiring high efficiency.

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13
Q

What is an AC motor?

A

An AC (Alternating Current) motor is an electric motor that converts AC electrical energy into mechanical energy. It operates using a rotating magnetic field produced by alternating current.

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14
Q

What are the two main types of AC motors?

A

Synchronous Motor – Runs at constant speed (sync speed with supply frequency).

Induction Motor (Asynchronous) – Runs slightly slower than sync speed due to slip.

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15
Q

Define AC power.

A

AC (Alternating Current) power is an electric current that periodically reverses direction, changing magnitude over time. It is the standard form of electricity for homes and industries.

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16
Q

Why is AC power widely used?

A

Easy voltage transformation (using transformers).

Lower energy loss over long distances (high-voltage transmission).

Simpler motor design (induction & synchronous motors).

Compatible with household and industrial grids.

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17
Q

What is a DC motor?

A

A DC (Direct Current) motor converts DC electrical energy into mechanical energy. It operates using a stationary magnetic field and a rotating armature powered by direct current.

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18
Q

What are the main types of DC motors?

A

Brushed DC Motor – Uses brushes and a commutator for current reversal.

Brushless DC Motor (BLDC) – Uses electronic controllers instead of brushes.

Series, Shunt, and Compound Motors – Differ in field winding connections.

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19
Q

Define DC power.

A

DC (Direct Current) power is an electric current that flows in one direction with a constant voltage. Examples: Batteries, solar cells, and rectifiers.

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20
Q

What is the main difference between an AC and DC generator?

A

AC Generator: Produces alternating current (voltage reverses direction periodically) using slip rings.

DC Generator: Produces direct current (unidirectional flow) using a commutator to convert AC to DC.

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21
Q

What are spur gears?

A

Teeth: Straight and parallel to the gear axis.

Advantages: Simple design, high efficiency, cost-effective.

Disadvantages: Noisy at high speeds, can’t handle heavy loads.

Applications: Clocks, washing machines, simple gearboxes.

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22
Q

How do helical gears work?

A

Teeth: Angled (helical) to the gear axis.

Advantages: Smoother and quieter operation than spur gears, higher load capacity.

Disadvantages: More complex, produces axial thrust.

Applications: Automotive transmissions, industrial machinery.

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23
Q

Where are bevel gears used?

A

Teeth: Conical shape, mounted on intersecting shafts (usually 90°).

Types: Straight, spiral, and hypoid.

Advantages: Transmits power between perpendicular shafts.

Applications: Differential drives, hand drills, marine propulsion.

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24
What makes worm gears unique?
Design: Worm (screw-like) meshes with a worm wheel. Advantages: High reduction ratio, self-locking (irreversible). Disadvantages: Low efficiency, generates heat. Applications: Elevators, conveyor systems, tuning instruments.
25
How does a rack and pinion system work?
Components: Linear rack + rotating pinion gear. Advantages: Converts rotational motion to linear motion (or vice versa). Disadvantages: Limited travel distance. Applications: Steering systems in cars, CNC machines.
26
Why are planetary gears special?
Design: Central sun gear, planet gears, and outer ring gear. Advantages: Compact, high torque density, balanced load distribution. Disadvantages: Complex design. Applications: Automatic transmissions, robotics, wind turbines.
27
What is Pascal's Law?
"A change in pressure applied to an enclosed incompressible fluid is transmitted undiminished to all portions of the fluid and to the walls of its container." Formula: Pressure (P) = Force (F) / Area (A)
28
What is the core principle behind Pascal's Law?
Fluid Behavior: Pressure acts equally in all directions in a confined fluid. Incompressibility: Works only with liquids (e.g., oil, water), not gases. Force Multiplication: Small force on a small area creates larger force on a bigger area (P₁ = P₂).
29
what is induced EMF?
The voltage generated in a conductor when exposed to a changing magnetic field. Caused by electromagnetic induction (Faraday's Law).
30
State Faraday's Law.
"The induced EMF in a circuit is proportional to the rate of change of magnetic flux through the circuit."
31
what is magetic flux
Magnetic flux is a measure of the total magnetic field which passes through a given surface.
32
What is a transducer?
A device that converts one form of energy into another (e.g., electrical ↔ mechanical, thermal ↔ electrical). Input: Physical quantity (e.g., temperature, pressure, light). Output: Electrical signal (e.g., voltage, current). Example: Microphone (sound → electrical signal).
33
How are transducers classified?
Active vs. Passive: Active: Requires external power (e.g., thermocouple). Passive: No external power (e.g., piezoelectric sensor). Input/Output: Sensor: Detects physical quantity (input → electrical). Actuator: Converts electrical → physical output (e.g., motor).
34
Name 5 common transducers and their functions.
Thermocouple: Temperature → Voltage. Strain Gauge: Force/Pressure → Resistance change. LVDT (Linear Variable Differential Transformer): Displacement → Voltage. Piezoelectric Sensor: Vibration → Charge. Photodiode: Light → Current.
35
What are key transducer properties?
Sensitivity: Output change per input unit (e.g., mV/°C). Linearity: Output proportionality to input. Resolution: Smallest detectable input change. Dynamic Range: Min/max measurable input.
36
Where are transducers used?
Medical: Ultrasound probes, ECG electrodes. Automotive: Oxygen sensors, throttle position sensors. Industrial: Pressure sensors in pipelines. Consumer Electronics: Touchscreens (capacitive transducers).
37
How does a piezoelectric transducer work?
Mechanical stress → Voltage (e.g., quartz crystals). Reverse Effect: Voltage → Mechanical deformation (used in buzzers). Applications: Gas lighters, inkjet printers.
38
What is the piezoelectric effect?
Direct Effect: Mechanical stress → Electric charge (used in sensors). Reverse Effect: Electric field → Mechanical deformation (used in actuators). Key Feature: Reversible energy conversion (mechanical ⇄ electrical).
38
Name common piezoelectric materials.
Natural: Quartz (SiO₂), Rochelle salt. Synthetic: PZT (Lead Zirconate Titanate), PVDF (Polymer). Property: Non-centrosymmetric crystal structure.
39
What is an actuator?
A device that converts energy (electrical, hydraulic, etc.) into mechanical motion. Function: Controls or moves a system (e.g., valves, robots, locks).
40
Name 4 common actuator types.
Electric: Solenoids, motors (DC, stepper, servo). Hydraulic: Uses fluid pressure (e.g., car brakes). Pneumatic: Uses compressed air (e.g., factory robots). Piezoelectric: Precision motion via piezoelectric effect.
41
How does an electric actuator work?
Input: Current flows through coils/windings. Magnetic Field: Interacts with permanent magnets/rotor. Motion: Rotor spins (rotary) or plunger moves (linear). Example: Servo motor uses feedback for precise angular control.
42
What’s a smart actuator?
Integrates sensors + control logic (e.g., IoT-enabled). Features: Self-calibration, fault detection. Use Case: Smart HVAC systems adjusting vents in real-time.
43
What is a sensor?
A device that detects and responds to a physical stimulus (e.g., light, heat, motion). Output: Converts input into readable signal (electrical, optical).
44
Differentiate active and passive sensors.
Active: Requires external power, emits energy to detect (e.g., radar, ultrasonic). Passive: Measures ambient energy (e.g., thermocouple, photodiode). Key Difference: Power requirement.
45
Compare analog and digital sensors.
Analog: Outputs continuous signal (e.g., potentiometer, analog temperature sensor). Digital: Outputs discrete values (e.g., digital accelerometer, encoder). Advantage: Digital sensors resist noise better.
46
Name 5 physical quantity sensors.
Temperature: Thermocouple, RTD. Pressure: Piezoelectric, MEMS. Proximity: Ultrasonic, capacitive. Force/Load: Strain gauge. Position: LVDT, encoder.
47
Name 5 environmental sensors.
Humidity: Capacitive hygrometer. Gas: CO₂ (NDIR), methane (semiconductor). Light: Photoresistor, photodiode. Sound: Microphone (piezoelectric). Motion: PIR (Passive Infrared).
48
How do inductive/capacitive sensors work?
Inductive: Detects metals via eddy currents. Capacitive: Detects any material by capacitance change. Use Case: Inductive for factory automation; capacitive for liquid level.
49
What are MEMS sensors?
Micro-Electro-Mechanical Systems (miniaturized devices). Examples: Accelerometers (smartphones), gyroscopes (drones). Advantage: Small size, low power.
50
What makes a sensor "smart"?
Integrates processing + communication (e.g., IoT sensors). Features: Self-calibration, data logging. Example: Smart thermostat (learns user behavior).
51
Why calibrate sensors?
Ensures accuracy by comparing to a standard. Methods: Zero/span adjustment, curve fitting.
52
What is fluid power?
A technology that uses pressurized fluids (liquids or gases) to transmit and control power. Two Types: Hydraulics: Uses oil/water (high power, precise control). Pneumatics: Uses compressed air (fast, clean, lower force).
53
How does Pascal’s Law apply to fluid power?
"Pressure applied to a confined fluid is transmitted equally in all directions." Formula: P=F/A → Force multiplication (small input → large output). Example: Hydraulic jack lifts heavy cars with minimal effort.
54
Name 5 key components of a hydraulic system.
Pump: Generates flow (e.g., gear pump). Actuator: Converts pressure to motion (cylinder/motor). Valves: Control flow/pressure (e.g., relief valve). Reservoir: Stores fluid. Hoses/Pipes: Transport fluid.
55
What are the main parts of a pneumatic system?
Compressor: Pressurizes air. Actuator: Pneumatic cylinder/rotary motor. Valves: Directional control (e.g., 5/2 valve). Air Treatment Unit: Filters/dries air. Exhaust: Releases used air.
56
What are the benefits of fluid power?
✓ Hydraulics: High force, precise motion, overload protection. ✓ Pneumatics: Clean, fast, explosion-proof. ✗ Limitations: Hydraulics leak; pneumatics compress (less precise).
56
Define viscosity
Fluid’s resistance to flow (critical for hydraulics).
57
define cavitation
Bubble formation damaging pumps (avoid low pressure!)
58
What is an open-loop vs. closed-loop system?
Open-Loop: No feedback; output has no effect on control (e.g., toaster, electric fan). Closed-Loop: Uses feedback to adjust output (e.g., thermostat, cruise control).
58
Draw block diagrams for both systems.
Open-Loop: Input → Controller → Actuator → Output Closed-Loop: Input → Controller → Actuator → Output → Sensor → Feedback → Comparator
59
Give 2 examples of each system.
Closed-Loop: Air conditioner (thermostat), autopilot system.
60
Compare advantages.
open loop- simpler/cheap desighn, no stability issues, fast response. closed-loop- higher accuracy, reduces errors(self correcting), tolerates disturbances.
61
Compare limitations.
open loop- no error correction, sensitive to disturbances, less precise. closed loop- complext/ expensive, risk of instability, slower due to feedback loop
62
Why is feedback critical in closed-loop systems?
Error Detection: Compares output to desired input (via comparator). Correction: Adjusts actuator to minimize error (e.g., PID controller).
63
What makes servo motors unique?
Closed-loop system: Uses feedback (encoder/potentiometer) for precise position/speed control. Components: Motor + control circuit + feedback device. Advantages: High torque at low speeds, accurate positioning. Applications: Robotics, CNC machines, RC vehicles.
64
What is a microcontroller (MCU)?
A compact integrated circuit with a processor, memory, and programmable I/O. "Computer-on-a-chip": Combines CPU, RAM, ROM, timers, and peripherals. Key Feature: Designed for embedded systems (dedicated tasks).
65
difference between microcontroller and microcomputer
microcontroller- low power, low electricicty usage, all in one chip, cheap. microcomputer- can multitask, high performance
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