Unit 1 electric drive

SOLID STATE DRIVES
UNIT -1
DRIVE CHARACTERISTICS
1
Dr.A.Ravi,
Professor,
Electrical and Electronics Engineering
Francis Xavier Engineering
College,Tirunelveli

Dr.A.Ravi Francis Xavier Engineering College,Tirunelveli

Electrical Energy (Rotational Force) Mechanical Energy
Motor
5

Define:
Electrical Drive
System employed for motion control of Electrical Motor is called Electrical Drives
Control Unit Motor
+
6

DEFINITION OF ELECTRICAL DRIVES
7

ADVANTAGES OF ELECTRICAL DRIVE
 Drives can be provided with automatic fault detection systems.
Programmable logic controller and computers can be
employed to automatically control the drive operations in a
desired sequence.
 They are available in wide range of torque, speed and power.
 They are adaptable to almost any operating conditions such
as explosive and radioactive environments
 It can operate in all the four quadrants of speed-torque plane
 They can be started instantly and can immediately be fully
loaded Control gear requirement for speed control, starting
and braking is usually simple and easy to operate.
8

APPLICATION
 Paper mills
 Cement Mills
 Textile mills
 Sugar Mills
 Steel Mills
 Electric Traction
 Petrochemical Industries
 Electrical Vehicles
9

ELECTRIC DRIVE
Group drive
Individual drive
Multi motor drive
10

GROUP DRIVE
11

INDIVIDUAL DRIVE
12

MULTI MOTOR DRIVE
13

GENERAL ELECTRIC DRIVE SYSTEM
14

PARTS OF ELECTRIC DRIVES
 Electrical Motor
 Power Modulator (Electronic Converter)
 Sources
 Control Unit
 Sensing Unit
15

TYPES OF DRIVES
 AC Drives
 DC Drives
16

AC DRIVE VS DC DRIVE
DC Drives AC Drives
Power circuit and control circuit is simple Complex
Frequent maintenence Less maintenence
The commutator makes the motor bulky costly and
heavy
hese problems are not there. so motors are
inexpensive, particularly the squirrel cage
motor
Speed And design rating are limited due to
commutation
Speed And design rating have no upper limits
The line conditions or very poor ie poor power factor,
harmonic distortion of the current
In solid state control, the speed range is wide
and in conventional method it is stepped and
limited
Power or weight ratio is small. Large
The line conditions or very poor ie poor power factor,
harmonic distortion of the current
for regenerative drives the line powerfactor is
poor for non regenerative drives the line
power factor is better 17

DYNAMICS OF MOTOR LOAD SYSTEM
18

19
J – Moment of inertia of the motor-load system referred to the
motor shaft (kg-m2)
ωm - Instantaneous angular velocity of motor shaft (rad/sec)
T - Instantaneous value of developed motor torque (Nm)
Tl - Instantaneous value of load torque referred to motor shaft
(Nm)
  m
l m m
dd dJ
Te T J J
dt dt dt

    

20

LOADS WITH ROTATIONAL SYSTEM
21

LOADS WITH ROTATIONAL SYSTEM
22

LOADS WITH TRANSLATIONAL SYSTEM
23

24
•If the transmission losses are neglected, then kinetic energy due to
equivalent inertia J must be the same as kinetic energy of various
moving parts. Thus
power at the motor and load should be the same, thus if efficiency of
transmission be η1
Dr.A.Ravi Francis Xavier Engineering College

 If, in addition to one load directly coupled to the
motor shaft, there are m other loads with
translational motion with velocities υ1,υ2, . . . υm and
masses M1,M2, . . . , Mm, respectively, then
25

Motor Duty Classification:
• Continuous Duty
• Short Time Duty
• Intermittent Periodic Duty
• Intermittent Periodic Duty with starting
• Intermittent Periodic Duty with staring and braking
• Continuous Duty with Periodic loading.
• Continuous Duty with Starting and Braking.
• Continuous Duty with periodic speed changes
26

T (Time)
Load
Torque
Temp
Rise
Continuous Duty:
• This represents the motor operation at a constant
load-enough for the motor temperature to reach
steady state value.
• Eg- Paper drive, Compressor, Conveyer
T (Time)
27

T (Time)
Load
Torque
Temp
Rise
Short Time Duty:
• In this type of operation the motor is operated for a
short period, which is less than the heating time
constant of the motor.
• Eg- Crane drive, House hold Application valve, etc.
T (Time)
28

T (Time)
Load
Torque
Temp
Rise
Intermittent periodic Duty:
• In this type of operation has number of duty
cycle which contains period of running at a
constant load and rest period .
T (Time)
29

Load
Torque
Temp
Rise
Intermittent periodic Duty with starting:
• In has starting running and constant load resting
periods. The rest period is short compared to the time
required to cool of to ambient temp.
• Eg:- Metal cutting and drilling tool drives
T (Time)T (Time)
Starting
Normal
operation

Load
Torque
Temp
Rise
Intermittent periodic Duty with starting & Braking:
• In this operation contains of a period of starting, a
period of operation, a constant load and a rest period:
with operating at rest period being too short for the
respective steady state temp to be attained .
• Eg:- Billet Mill drives, /manipulator drive, electric
Suburban drive
T (Time)
T (Time)

m
Te
Te
m
Te
m
Te
m

T
• Direction of positive (forward)
speed is arbitrary chosen
• Direction of positive torque will
produce positive (forward) speed
Quadrant 1
Forward motoring
Quadrant 2
Forward braking
Quadrant 3
Reverse motoring
Quadrant 4
Reverse braking
FOUR QUADRANT (MULTIQUADRANT) OPERATION OF
MOTOR USING HOIST LOAD
32Dr.A.Ravi Francis Xavier Engineering College,Tirunelveli

Torque-speed quadrant of operation

T
12
3 4
T +ve
 +ve
Pm +ve
T -ve
 +ve
Pm -ve
T -ve
 -ve
Pm +ve
T +ve
 -ve
Pm -ve
• Quadrant of operation is
defined by the speed and
torque of the motor.
• Most rotating electrical
machines can operate in
4 quadrants.
• Not all converters can
operate in 4 quadrants.
33

MULTI QUADRANT DRIVE
34

MULTI QUADRANT DRIVE
35

1st Quadrant (Forward Motoring):
 The torque and speed of the motor are in the same direction. Of
course, the load torque is opposite to the machine torque.
 The electrical machine in this case is operating as a motor. The
flow of power is from the machine to the load.
2nd Quadrant (Forward Braking):
 The speed direction is unchanged while the direction of the torque is
reversed.
 Since the load torque direction is in the same direction of speed, the
mechanical load is delivering power to the machine.
 The machine then receives mechanical energy, converting it in to electrical
energy and returning it back to the electric source. The electric machine is
thus acting as a Generator. 36

3rd Quadrant (Reverse Motoring):
 Compared to the first quadrant, the system speed and torque are
reversed in the third quadrant.
 Since the torque and speed of the machine are in the same
direction, the power flow is from the machine to the load. The
machine is therefore acting as a motor rotating in the reverse
direction to the speed of the first quadrant.
 Bidirectional grinding machine is the good example of the 1st and
3rd quadrant operation. The direction of the load torque of the
grinding load is reversed when the speed is reversed (3rd
quadrant). A horizontal conveyor belt is another example of this
type of operation.
37

4th Quadrant (Reverse Braking):
 The torques remains unchanged as compared to the first quadrant.
The speed, however, changes the direction.
 From the load perspective, the load torque and the speed are in the
same direction. Hence the power flow is from the load to the
machine.
 The machine is in this case acting as generator delivering the
electric power to the source.
 The first and fourth quadrant of operation can be explained with the
elevator. When the elevator is going upward or downward, the
direction of the load torque remains unchanged but the direction of
the speed only reversed.
38

WHAT SIZE MOTOR TO SELECT
 How much power is needed
 How much electrical power is available
 Do you have enough capacity in service entrance
panel (breaker box)
39

 Operating temperature and cooling
 Torque per unit volume
 Power per unit volume – importance of speed
 Size effects – specific torque and efficiency
 Efficiency and speed
 Rated voltage
 Short-term overload
40

MOTOR ON NEW EQUIPMENT
 Use equipment manufacturer’s recommendation
41

POWER SUPPLY
 3-Phase, 208, 230 or more volts
 4 wires in power line
 up to 1,000 hp
 little or no light flickering
 cost less
 last longer
 pay extra to install 3-phase power lines
42

MOTOR DUTY
 Motor Duty = amount of time the motor is operating
under full load, and how much time it is stopped
 Continuous Duty: constant full load for over 60
minutes at a time
 Intermittent Duty: fully loaded for 5, 15, 30, or 60
minutes
43

STARTING LOADS
 Easy Starting Loads:
 Shaded Pole Induction
 Split Phase
 Permanent-Split, Capacitor-Induction
 Soft-Start
44

STARTING LOADS
 Difficult Starting Loads
 Capacitor-Start, Induction-Run
 Repulsion-Start, Induction-Run
 Capacitor-Start, Capacitor-Run
 Three-Phase, General-Purpose
 Perkey Concept: use tractor PTO to start
 Repulsion-Start, Capacitor-Run
45

OTHER FACTORS TO CONSIDER
 Direction of Rotation
 Cost
 Maintenance
 motors with brushes cause radio interference
 repulsion-start interferes at starting
 motors with brushes require more maintenance
46

BEARING TYPES
 Sleeve Bearings: brass, bronze or tin lined cylinder
 Ball Bearings: round steel balls surround the shaft
in a special cage
47

LUBRICATION: SLEEVE BEARINGS
 Yarn Packed: add few drops of oil every few months
to yarn
 Ring Oiled: ring spins freely in oil reservoir
 keep oil level up to fill plug
48

LUBRICATION: BALL BEARINGS
 Prelubricated and Sealed: no maintenance required
 Hand Packed: disassemble bearing and hand pack
with grease every 2-5 years
 Special Fittings: filler and drain plug
 remove bottom plug before greasing
49

MOUNTING BASE
 Rigid (fixed to frame)
 Rigid (adjustable screws)
 Sliding Rails
50

MOTOR DRIVES
 Direct: connect motor to equipment
Flexible-Hose Coupling
Flange Coupling: flange attaches to motor, another to
equipment, flanges attach to flexible disk
Cushion-Flange Coupling: tire shaped cushion between
flanges
Flexible Shaft: direction of rotation is important
51

SPEED-CONVERSION DRIVES
 Gear Drive
 Chain-and-Sprocket Drive
 Pulley-and-Belt Drive: pulleys connected by continuous
belt loop
V-Belt
Webbed Multi-V-Belt
Flat-Belt
V-Flat
52

WHAT SIZE OF DRIVE TO SELECT
 Shaft Size (Bore)
 Some pulleys come with several bushings to fit
several sizes of shafts
53

PULLEY TYPES
 Standard V-Pulley
 V-Step Pulley
 Adjustable V-Pulley
54

SIZING PULLEYS
 Pulley Selection Chart (p.49)
 Size of pulley on motor
 under 1/2 hp, keep pulley under 2” diameter
 over 1/2 hp, pulley 3” or larger
 Move across chart to desired equipment speed
 Move up to find equipment pulley size
55

STEADY STATE STABILITY
 Equilibrium speed of a motor load system is obtained when
the motor torque, Te equals the load torque T l.
Stable state of equilibrium point
 The equilibrium point is termed as stable, if the operating
point is restored after a small departure from it due to
disturbance in the motor or load.
Unstable state of equilibrium point
 The equilibrium point is termed as stable, if the operating
point will not be restored after a small departure from it due
to disturbance in the motor or load.
56

MATHEMATICAL CONDITION FOR THE STABILITY OF THE
EQUILIBRIUM POINT
57

 Possible with variable frequency converter.
 Variable frequency synchronous motor can be
controlled to posses the characteristics of a
separately excited dc motor.
58

59

Unit 1 electric drive

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Unit 1 electric drive