2. UNIT-1
INTRODUCTION TO ELECTRIC DRIVES
General block diagram of electrical drive-Types
of Electric Drives–Factors influencing the choice
of electrical drives– heating and cooling curves–
classes of duty – Multi Quadrant operation of
Electric Drives
3. DEFINITION
• DRIVE
The machines employed for motion control
is called drive
• ELECTRICAL DRIVE:
The electrical machines employed
for motion control is called electrical drive
4. ADVANTAGES OF ELECTRICAL DRIVE:
• Flexible
• Available in wide range of torque, speed and
power
• Adaptable to all environment
• Four quadrant operation is possible
• Started and stopped instantly
• Simple control gear
8. Choice or selection of electrical drive:
• Steady state operation requirement
• Transient operation requirement
• Requirements related to source
• Capital cost, running cost, maintenance needs,
life
• Space and weight restrictions
• Environment and location
• Reliability
17. What are some things that happen as
we heat a sample up?
• Solid Liquid Gas
• Melting, Evaporating
18. What is heat? How is heat different from
temperature?
• Heat is a measure of kinetic or translational energy
– In chemistry heat is measure in Joules (J)
– Heat is dependent on mass, temperature change and
specific heat (or ability of a substance to absorb heat)
• Temperature is a measure of warmth or coldness.
– Temperature is independent of heat
– Temperature is measured in Kelvin (K) or Celsius (C)
19. What is the heating curve?
• The heating curve is a graph which represents how a sample
changes phases. As heat is added over time, the sample
changes temperature and phase accordingly. Thus heating
curve.
27. Why is the curve flat at some
portions?
• Temperature is staying
constant, but potential
energy is decreasing
• During this time the
solid completely
becomes liquid (or
liquid becomes solid)
28. Why is the curve flat at some points?
• This is called the heat of
fusion (Hf) in segment
BC and heat of
vaporization (Hv) in
segment DE.
• Remember fusion is
melting and
vaporization is
evaporation
29. What is heat of fusion? What is heat of
vaporization?
• Hf is the amount of
energy needed to
completely make a solid
into a liquid
• Hv is the amount of
energy needed to
completely make a
liquid into a gas
30. SELECTION OF POWER RATING FOR DRIVE MOTORS
WITH REGARD TO THERMAL OVERLOADING AND
LOAD VARIATION FACTORS
• Selection of electrical motor
• Types of enclosures
• Selection of motor rating
31. 1.Selection of electrical motor
• Squirrel cage induction motor
• Slip ring induction motor
• Synchronous motor
• DC shunt or compound motor
• DC series motor
• AC commutator motor
• Stepper motor
32. 2. Types of enclosures
• Screen protected type
• Drip proof type
• Totally enclosed type
• Flame proof type
33. 3. Selection of motor rating
• Continuous duty load
• Short time duty load
• Intermittent duty load
34. Heating and cooling of an electric
motor
• Assumptions
• The machine is considered to be a
homogeneous
• The rate of dissipation of heat is constant at all
temperatures
• Heat dissipation is directly proportional to (T1-
T2)
37. CONVENTIONAL AND SOLID STATE
SPEED CONTROL OF D.C. DRIVES
Conventional speed control methods of DC
shunt motor and DC series motor- Ward-
Leonard speed control-Solid state speed
control using controlled rectifiers : Single
phase semi and Full converter drives, Three
Phase semi and Full converter drives ,Chopper
fed DC Drives – Application : Cranes and Hoist
Drives
49. Solid state speed control of DC motor:
• Trough power semiconductor devices.
• Types of DC drives
• Phase controlled rectifier fed DC drives
• Chopper fed DC drives.
50. Phase controlled converter fed DC
drives
• Advantages
• Simple and reliable, fast response, high
efficiency, small size, less weight, low initial
cost.
• Disadvantages
• Motor heating due to ripple content,
interference problem, complex control circuit
to achieve regeneration.
51. Single phase converter drive:
• Single phase half wave converter
drives
• Single phase semi converter drives.
• Single phase fully controlled
converter drives.
52. DC chopper fed drive
• DC chopper converts fixed DC into variable DC
voltage
• Advantages:
• High efficiency, flexibility in control, light
weight, small size, quick response,
53. • Applications
• Battery operated vehicles
• Traction motor control in electric traction
• Hoists
• Electric braking
54. Types of chopper fed drives:
• First quadrant chopper (Type A chopper)
• Second quadrant chopper (Type B chopper)
• Two quadrant type A quadrant chopper (Type
C chopper)
• Two quadrant type B quadrant chopper (Type
D chopper)
• Four quadrant chopper (type E chopper)
55. Control strategies:
• Types:
• Time ratio control (TRC)
• (a) constant frequency system
• (b) variable frequency system
• (i) ON time is kept constant
• (ii) OFF time is kept constant
• Current limit control (CLC)
