‫كلية تكنولوجيا الصناعة والطاقة‬

Hybrid Vehicles
Autotronics Program
q
Dr. Mohamed Essam
Lec. 3 February 2024
 Electric Vehicles Types ‫كلية تكنولوجيا الصناعة والطاقة‬
• Electric Vehicle (EVs) or Electrically Chargeable Vehicles (ECVs) usually refers to any vehicle that is
powered, in part or in full, by a battery that can be directly plugged into the mains.
• EV is used as the general description for all types of electric vehicle.
• Pure-Electric Vehicles (Pure-EVs) are electric vehicles powered only by a battery.
Plug-In Hybrid Electric Vehicles (PHEVs)
• They have an internal combustion engine (ICE) but also a battery. After the battery range is
utilized, the vehicle reverts to the benefits of full hybrid capability (utilizing both battery and ICE
power) without compromising the range.
Extended-Range Electric Vehicles (E-REVs)
• They are similar to pure-EVs but with a shorter battery range. However, range is extended by an
ICE-driven generator providing many additional miles of mobility. With an E-REV, the propulsion is
always electric, unlike a PHEV where the propulsion can be electric or full hybrid.
‫كلية تكنولوجيا الصناعة والطاقة‬
 Electric Vehicles Types ‫كلية تكنولوجيا الصناعة والطاقة‬
• Electricity, when produced from sustainable sources, is easy to supply and produces no emissions
from the vehicle (often described as tailpipe emissions). EVs therefore have significant
environmental benefits, particularly when used in urban environments. Some of the benefits of
EVs when operating solely on battery power are:
• zero tailpipe emissions and quiet driving
• easy to drive, particularly in stop–start traffic
• home charging avoids fuel station queues.
• Electric vehicles can now achieve similar speeds to ICE vehicles during normal driving. Some pure-
electric cars can reach speeds over 125 mph where permitted. Power is delivered by the electric
motor as soon as the vehicle begins to move, which gives smooth and swift acceleration.
• EVs have to comply with the same safety standards as conventional cars by obtaining ‘whole
vehicle type approval’. Individual components such as the battery pack are also subjected to
additional impact and other mechanical tests.
• EVs typically use an inertia switch or a signal from the airbag system to disconnect the traction
battery if the vehicle is involved in a collision. This is very similar to conventional vehicles, where
an inertia switch is provided to stop the fuel supply in a crash. Battery packs are also designed
with internal contactors so that if the 12 V supply is cut for any reason, the traction supply is also
shut off.
 Electric Vehicles Types
‫كلية تكنولوجيا الصناعة والطاقة‬
• Electric vehicles have zero emissions at the point of use, so-called ‘tank-to-wheel’, when powered
only by the battery. The ‘well-to wheel’ analysis includes the CO2 emissions during electricity
generation, which depends on the current mixture of fuels used to make the electricity for the
grid.
• To make a correct comparison with emissions from all cars, it is necessary to use the ‘well-to-
wheel’ figure, which includes the CO2 emissions during production, refining and distribution of
petrol/ diesel.
• Electricity production continues to decarbonize because of reduced reliance on oil and coal, so the
overall emission figure for running an EV will drop further. Tailpipe emissions also include oxides
of nitrogen (NOx) and particulate matter (tiny particles of solid or liquid matter suspended in a gas
or liquid) that contribute to air pollution. This is why any vehicle operating only on battery power
will play a significant role in improving local air quality.
 Electric Vehicles Safety
‫كلية تكنولوجيا الصناعة والطاقة‬
• Electric vehicles (pure or hybrid) use high voltage batteries so that energy can be delivered to a
drive motor or returned to a battery pack in a very short time.
• The Honda Insight system, for example, uses a 144-V battery module to store re-generated energy.
The Toyota Prius originally used a 273.6-V battery pack but this was changed in 2004 to a 201.6-V
pack.
• Voltages of 300 V are now common and some up to 700 V, so clearly there are electrical safety
issues when working with these vehicles.
 Electric Vehicles Safety
‫كلية تكنولوجيا الصناعة والطاقة‬
• Most of the high-voltage components are combined in a power unit. This is often located behind
the rear seats or under the luggage compartment floor (or the whole floor in a Tesla). The unit is a
metal box that is completely closed with bolts.
• The electric motor is located between the engine and the transmission or as part of the
transmission on a hybrid or on a pure-EV; it is the main driving component. A few vehicles use
wheel motors too.
• The electrical energy is conducted to or from the motor by thick orange wires. If these wires have
to be disconnected, SWITCH OFF or DE-ENERGISE the high-voltage system. This will prevent the
risk of electric shock or short circuit of the high-voltage system.
 Electric Vehicles Safety Guidance
‫كلية تكنولوجيا الصناعة والطاقة‬
Before maintenance:
• Turn OFF the ignition switch and remove the key.
• Switch OFF the battery module switch or de-energize the system.
• Wait for 5 minutes before performing any maintenance procedures on the system. This allows any
storage capacitors to be discharged.
During maintenance:
• Always wear insulating gloves.
• Always use insulated tools when performing service procedures to the high voltage system. This
precaution will prevent accidental short-circuits.
Interruptions:
• When maintenance procedures have to be interrupted while some high-voltage components are
uncovered or disassembled, make sure that:
• The ignition is turned off and the key is removed.
• The battery module switch is switched off.
• No untrained persons have access to that area and prevent any unintended touching of the
components.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Electric Vehicles Safety Guidance
After maintenance:
Before switching on or re-energizing the battery module after repairs have been completed, make
sure that:
• All terminals have been tightened to the specified torque.
• No high-voltage wires or terminals have been damaged or shorted to the body.
• The insulation resistance between each high-voltage terminal of the part you disassembled and
the vehicle’s body has been checked.
• The voltages (AC or DC) used on electric vehicles can kill, have killed and will kill
again.
• The three basic factors that determine what kind of shock you experience when current passes
through the body are:
• Size of the current
• Duration
• frequency.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Electric Vehicles Safety Guidance
• Direct currents actually have zero frequency, as the current is constant. However, there are
physical effects during electrocution no matter what type of current.
• The factor deciding the effects of the AC and DC current is the path the current takes through the
body. If it is from the hand to the foot, but it does not pass through the heart, then the effects
might not be lethal.
• However, DC current causes a single continuous contraction of the muscles compared with AC
current, which will make a series of contractions depending on the frequency. In terms of
fatalities, both kill but more milliamps are required of DC current than AC current at the same
voltage.
• If the current takes the path from hand to hand, thus passing through the heart, it can result in
fibrillation of the heart. It affects the ability of the heart to pump blood, resulting in brain damage
and eventual cardiac arrest.
• Either AC or DC currents can cause fibrillation of the heart at high enough levels. This typically
takes place at 30 mA of AC (rms, 50–60 Hz) or 300–500 mA of DC.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Electric Vehicles Safety Guidance
Facts about electric shock
• It is the magnitude of current and the duration that produces effect. That means a low-value
current for a long duration can also be fatal. The current/time limit for a victim to survive at 500
mA is 0.2 seconds and at 50 mA is 2 seconds.
• The voltage of the electric supply is only important because it ascertains the magnitude of the
current. As Voltage = Current × Resistance, the bodily resistance is an important factor. Sweaty or
wet persons have a lower body resistance and so they can be fatally electrocuted at lower
voltages.
• Severity of electric shock depends on body resistance, voltage, current, path of the current, area
of contact and duration of contact.
‫كلية تكنولوجيا الصناعة والطاقة‬
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Electric Vehicles Configurations
• Electric propulsion replaces the IC engine of a conventional vehicle drive train. It consists of an
electric motor, a clutch, a gearbox, and a differential. The clutch and gearbox may be replaced by
an automatic transmission. The clutch is used to connect or disconnect the power of the electric
motor from the driven wheels. The gearbox provides a set of gear ratios to modify the speed-
power (torque) profile to match the load requirement. The differential is a mechanical device
(usually a set of planetary gears), which enables the wheels of both sides to be driven at different
speeds when the vehicle runs along a curved path.
• With an electric motor that has constant power in a long speed range, a fixed gearing can replace
the multispeed gearbox and reduce the need for a clutch. This configuration not only reduces the
size and weight of the mechanical transmission, it also simplifies the drive train control because
gear shifting is not needed.
• Similar to the drive train in (b), the electric motor, the fixed gearing, and the differential can be
further integrated into a single assembly while both axles point at both driving wheels. The whole
drive train is further simplified and compacted.
• The mechanical differential is replaced by using two traction motors. Each of them drives one side
wheel and operates at a different speed when the vehicle is running along a curved path.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Electric Vehicles Configurations
• In order to further simplify the drive train, the traction motor can be placed inside a wheel. This
arrangement is the so-called in-wheel drive. A thin planetary gear set may be employed to reduce
the motor speed and enhance the motor torque. The thin planetary gear set offers the advantage
of a high-speed reduction ratio as well as an inline arrangement of the input and output shaft.
• By fully abandoning any mechanical gearing between the electric motor and the driving wheel,
the out-rotor of a low-speed electric motor in the in-wheel drive can be directly connected to the
driving wheel. The speed control of the electric motor is equivalent to the control of the wheel
speed and hence the vehicle speed. However, this arrangement requires the electric motor to
have a higher torque, to start and accelerate the vehicle.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
‫‪Propulsion System‬‬
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Propulsion System
• Electric propulsion systems are at the heart of EVs and HEVs. They consist of electric motors,
power converters, and electronic controllers.
• The electric motor converts the electric energy into mechanical energy to propel the vehicle, or
vice versa, to enable regenerative braking and/or to generate electricity for charging the on-board
energy storage.
• The power converter is used to supply the electric motor with proper voltage and current.
• The electronic controller commands the power converter by providing control signals to it, and
then it controls the operation of the electric motor to produce proper torque and speed,
according to the command from the driver.
• The electronic controller can be further divided into three functional units—sensor, interface
circuitry, and processor. The sensor is used to translate the measurable quantities, such as
current, voltage, temperature, speed, torque, and flux, into electric signals through the interface
circuitry. These signals are conditioned to the appropriate level before being fed into the
processor. The processor output signals are usually amplified via the interface circuitry to drive
power semiconductor devices of the power converter.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Propulsion System
• The choice of electric propulsion systems for EVs and HEVs mainly depends on several factors,
including the driver’s expectation, vehicle constraints, and energy source.
• The driver’s expectation is defined by a driving profile, which includes the acceleration, maximum
speed, climbing capability, braking, and range.
• The vehicle constraints, including volume and weight, depend on the vehicle type, vehicle weight,
and payload.
• The energy source relates to batteries, fuel cells, ultracapacitors, flywheels, and various hybrid
sources. Thus, the process of identifying the preferred feature and package options for electric
propulsion must be carried out at the system level. The interaction of subsystems and the likely
impacts of system trade-offs must be examined.
• The motors used in EVs and HEVs usually require frequent starts and stops, and a very wide speed
range of operation.
 DC Motor ‫كلية تكنولوجيا الصناعة والطاقة‬
• The operation principle of a DC motor is straightforward.
When a wire carrying electric current is placed into a magnetic
field, a magnetic force acting on the wire is produced. The
force is perpendicular to the wire and the magnetic field
• The magnetic force is proportional to the wire length,
magnitude of the electric current, and the density of the
magnetic field. When the wire is shaped into a coil, the
magnetic forces acting on both sides produce a torque.
• The magnetic field may be produced by a set of windings or
PMs. The former is called a wound-field DC motor, and the
latter is called a PM DC motor. The coil carrying electric current
is called the armature. In practice, the armature consists of
several coils. To obtain continuous and maximum torque, slip
rings and brushes are used to conduct each coil at a position of
α = 0.
• Typically, there are four types of wound-field DC motors,
depending on the mutual interconnection between the field
and armature windings. They are separately excited, shunt
excited, series excited, and compound excited.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
DC Motor
• In the case of a separately excited motor, the field and the armature voltage can be controlled
independently of one another.
• In a shunt motor, the field and the armature are connected in parallel to a common source. Therefore, an
independent control of field or armature currents can only be achieved by inserting a resistance in the
appropriate circuit. This is an inefficient method of control. The efficient method is to use power-
electronics-based DC–DC converters in the appropriate circuit to replace the resistance. The DC–DC
converters can be actively controlled to produce proper armature and field voltage.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
DC Motor
• In the case of a series motor, the field current is the same as the armature current; therefore, field flux is
a function of armature current.
• In a cumulative compound motor, the magnetomotive force (mmf) of a series field is a function of the
armature current and is in the same direction as the mmf of the shunt field.
 DC Motor
• In the case of separately excited motors, if the field voltage is ‫كلية تكنولوجيا الصناعة والطاقة‬
maintained as constant, one can assume the flux to be
practically constant as the torque changes. In this case, the
speed–torque characteristic of a separately excited motor is a
straight line.
• In the case of a series, any increase in torque is accompanied
by an increase in the armature current and, therefore, an
increase in magnetic flux. Because flux increases with the
torque, the speed drops to maintain a balance between the
induced voltage and the supply voltage. The characteristic,
therefore, shows a dramatic drop. A motor of standard design
works at the knee point of the magnetization curve at the
rated torque. At heavy torque (large current) overload, the
magnetic circuit saturates, and the speed–torque curve
approaches a straight line.
• Series DC motors are suitable for applications requiring high
starting torque and heavy torque overload, such as traction.
However, series DC motors for traction application have some
disadvantages. They are not allowed to operate without the
load torque with full supply voltage. Otherwise, their speed
quickly increases up to a very high value.
‫كلية تكنولوجيا الصناعة والطاقة‬
 ‫كلية تكنولوجيا الصناعة والطاقة‬
VOLTAGE SPEED CONTROL OF A SEPARATELY EXCITED DC MOTOR
• The field current, if , is constant (and hence the flux density is constant), and the armature voltage is
varied. A constant field current is obtained by separately exciting the field from a fixed dc source. The
flux is produced by the field current, therefore, essentials constant. Thus the torque is proportional only
to the armature current.
FIELD SPEED CONTROL OF A SEPARATELY EXCITED DC MOTOR
• We can also control the dc motor, that is vary its speed by varying the field flux. The method of control is
generally used when the motor has to run above its rated speed.
• If the field current is reduced by reducing the voltage across the field coil, the flux density will be
reduced. This will reduce the back emf instantaneously and will cause armature current to increase
resulting in the motor speed increasing. Consequently the back emf will increase and a new equilibrium
will be established at a higher speed.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Combined Armature Voltage and Field Control
• The independence of armature voltage and field provides more
flexible control of the speed and torque than other types of DC
motors. In EV and HEV applications, the most desirable speed–
torque characteristic is to have a constant torque below a certain
speed (base speed) and a constant power in a speed range above
the base speed.
• In a speed range lower than the base speed, the armature current
and field are set at their rated values, producing the rated torque.
• It is clear that the armature voltage must be increased
proportionally to the increase in speed. At the base speed, the
armature voltage reaches its rated value (equal to the source
voltage) and cannot be increased further. To further increase the
speed, the field must be weakened with the increase in speed,
then the back EMF E and armature current constant maintained.
• The torque produces drops parabolically with the increase in
speed, and the output power remains constant
 ‫كلية تكنولوجيا الصناعة والطاقة‬
H-bridge Concept Introduction
• An H-bridge is an electronic circuit that reverses the
voltage/current at both ends of the load or output to which it is
connected.
• These circuits are used in robots and other real-world applications
for DC motor inversion control and speed control, stepper motor
control.
• H-bridge is a typical DC motor control circuit because its circuit
shape resembles the letter H, so it is named with "H-bridge". 4
transistors form the 4 vertical legs of H, and the motor is the
horizontal bar in H.
• The H-bridge circuit can be built as discrete components or
integrated into an integrated circuit and is often used in inverters
(DC-AC conversion). Through the opening and closing of switches,
DC power (from batteries, etc.) is inverted into AC power of a
certain frequency or variable frequency, which is used to drive AC
motors (asynchronous motors, etc.).
 ‫كلية تكنولوجيا الصناعة والطاقة‬
H-bridge Operation

Forward
• Usually, the H-bridge is used to drive inductive loads, here we
drive a DC motor. Turn on Q1 and Q4. Turn off Q2 and Q3. At this
point, assuming the motor is forward, this current passes through
Q1, M, Q4 in turn, marked in the diagram using the yellow line
segment, as shown below.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
H-bridge Operation

Backward
• Another state is the motor backward; at this time the state of the
four switching components are as follows.
• Turning off Q1 and Q4.
• Turning on Q2 and Q3.
• At this point the motor reverses (opposite to the case described
earlier), which current passes through Q2, M, and Q3 in turn,
marked in the diagram using yellow lines, as shown in the figure.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
H-bridge Operation

Speed regulation
• If the DC motor is to be speed regulated, one of the options
is:
• Turning off Q2, Q3.
• Turning on Q1, giving it a 50% duty cycle PWM waveform on
Q4 so that the effect of reducing the speed is achieved, and
if the speed needs to be increased, setting the duty cycle of
the input PWM to 100%
 H-bridge Operation ‫كلية تكنولوجيا الصناعة والطاقة‬
Stop state
• Here the motor is switched from forward to stop state as an
example.
• In the case of forward, Q1 and Q4 are open. At this time, if
Q1 and Q4 are turned off, the DC motor internal can be
equivalent to an inductor, that is, inductive load, the current
will not change suddenly, then the current will continue to
maintain the original direction of flow.
• There are two approaches here. The first: close Q1 and Q4,
when the current will still flow through the reverse
continuity diode, then briefly open Q1 and Q3 so as to
achieve the purpose of rapid decay of the current. Motor
stop state circuit.
• The second: when preparing to stop, turn off Q1 and turn on
Q2. At this time, the current does not decay very quickly. The
current circulates between Q2, M, and Q4, and the power is
consumed by the internal resistance of the MOS-FET.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
AC motors
• In general, all AC motors work on the same principle. A three-phase winding is distributed round a
laminated stator and sets up a rotating magnetic field that the rotor ‘follows’. The general term is an AC
induction motor.
Asynchronous motor
• The asynchronous motor is often used with a squirrel cage rotor made up of a number of pole pairs. The
stator is usually three-phase and can be star or delta wound. The rotating magnetic field in the stator
induces an EMF in the rotor which, because it is a complete circuit, causes current to flow. This creates
magnetism, which reacts to the original field caused by the stator, and hence the rotor rotates. The
amount of slip (difference in rotor and field speed) is about 5% when the motor is at its most efficient.
Synchronous motor: permanent excitation
• This motor has a wound rotor, known as the inductor. This winding is magnetized by a DC supply via two
slip rings. The magnetism ‘locks on’ to the rotating magnetic field and produces a constant torque. If the
speed is less than n (see above), fluctuating torque occurs and high current can flow. This motor needs
special arrangements for starting rotation. An advantage, however, is that it makes an ideal generator.
The normal vehicle alternator is very similar.
 ‫كلية تكنولوجيا الصناعة والطاقة‬
Induction Motor Drives
• Commutatorless motor drives offer several advantages over conventional DC commutator motor drives
for the electric propulsions of EVs and HEVs.
• At present, induction motor drives are the mature technology among commutatorless motor drives.
Compared with DC motor drives, the AC induction motor drive has additional advantages such as its
lightweight nature, small volume, low cost, and high efficiency. These advantages are particularly
important for EV and HEV applications.
• There are two types of induction motors, wound-rotor and squirrel-cage motors. Because of the high
cost, need for maintenance, and lack of sturdiness, wound-rotor induction motors are less attractive
than their squirrel-cage counterparts, especially for electric propulsion in EVs and HEVs. Hence, squirrel-
cage induction motors are loosely referred to as induction motors.
 Induction Motor Drives ‫كلية تكنولوجيا الصناعة والطاقة‬

• A cross section of a two-pole induction motor is shown in

Figure. Slots in the inner periphery of the stator are inserted
with three phase windings, a–a′, b–b′, and c–c′.
• The turns of each winding are distributed such that the current
in the winding produces an approximate sinusoidally
distributed flux density around the periphery of the air gap. The
three windings are spatially arranged by 120◦.
• The most common types of induction motor rotors are the
squirrel-cage motors in which aluminum bars are cast into slots
in the outer periphery of the rotor. The aluminum bars are
short-circuited together at both ends of the rotor by cast
aluminum end rings, which also can be shaped as fans.
 Induction Motor Drives ‫كلية تكنولوجيا الصناعة والطاقة‬

• Figure shows, schematically, a cross section of the stator of a three-phase, two-pole induction motor.
• Each phase is fed with a sinusoidal AC current, which has a frequency of ω and a 120◦ phase difference
between each other.
• Current ias, ibs, and ics in the three stator coils a–a′, b–b′, and c–c′ produce alternative magnetic motive
forces (mmfs), Fas, Fbs, and Fcs, which are space vectors. The resultant stator mmf vector constitutes a
vector sum of the phase mmf vectors.
 Induction Motor Drives ‫كلية تكنولوجيا الصناعة والطاقة‬

• The reaction between the rotating stator mmf and the rotor conductors induces a voltage in the rotor
and electric current in the rotor. In turn, the rotating mmf produces a torque on the rotor, which is
carrying the induced current.
• The induced current in the rotor is essential for producing torque, and in turn, the induced current
depends on the relative movements between the stator mmf and the rotor. That is why there must
exist a difference between the angular velocity of the rotating stator mmf and the angular velocity of
the rotor.
• The frequency ω, or angular velocity of the rotating stator mmf, depends only on the frequency of the
alternative current of the stator; thus, it is referred to as electrical angular velocity. For a machine with
two poles, the electrical angular velocity is identical to the mechanical angular velocity of the rotating
stator mmf. However, for a machine with more than two poles, the mechanical angular velocity differs
from the electrical one.
• When the angular velocity of the rotor is equal to the mechanical angular velocity of the rotating stator
mmf, there is no induced current in the rotor, and then no torque is produced. Thus, the mechanical
angular velocity of the rotating stator mmf is also called synchronous speed.
 Induction Motor Drives ‫كلية تكنولوجيا الصناعة والطاقة‬

• For ωm < ωms, the relative speed is positive; consequently, the rotor-induced voltages have the same
phase sequence as the stator voltages. The three-phase current flowing through the rotor produces a
magnetic field, which moves with respect to the rotor at the slip speed in the same direction as the
rotor speed. Consequently, the rotor field moves in the space at the same speed as the stator, and a
steady torque is produced.
• For ωm = ωms, the relative speed between the rotor and the stator field becomes zero. Consequently,
no voltages are induced, and no torque is produced by the motor.
• For ωm > ωms, the relative speed between the stator field and the rotor speed reverses. Consequently,
the rotor-induced voltages and currents also reverse and have a phase sequence opposite to that of the
stator. Moreover, the developed torque has a negative sign, suggesting generator operation. (The
generator is used to produce regenerative braking.)
 Constant Volt/Hertz Control ‫كلية تكنولوجيا الصناعة والطاقة‬

• For traction application, the torque–speed characteristic of an induction motor can be varied by
simultaneously controlling the voltage and frequency, which is known as the constant volt/hertz
control. By emulating a DC motor at low speed, the flux may be kept constant.
• The field current Im should be kept constant and equal to its rated value. That is,

• Where Imr is the rated field current, and Erated and ωr are the rated mmf and frequency of the stator,
respectively. To maintain a constant flux, the E/ω should be kept constant and equal to Erated/ωr.
 Constant Volt/Hertz Control ‫كلية تكنولوجيا الصناعة والطاقة‬

• It was found with constant E/ω, the maximum torque is constant with varying frequency. In practice,
due to the presence of stator impedance and the voltage drop, the voltage should be somewhat higher
than that determined by constant E/ω.
• When the motor speed is beyond its rated speed, the voltage reaches its rated value and cannot be
increased with the frequency. In this case, the voltage is fixed to its rated value, and the frequency
increases continuously with the motor speed. The motor goes into the field weakening operation. The
slip s is fixed to its rated value corresponding to the rated frequency, and the slip speed ωsl increases
linearly with the motor speed. This control approach results in constant power operation.
• In traction applications, speed control in a wide range is usually required, and the torque demand in the
high-speed range is low. Control beyond constant power range is required.
• To prevent the torque from exceeding the breakdown torque, the machine is operated at a constant slip
speed, and the machine current and power are allowed to decrease.
‫كلية تكنولوجيا الصناعة والطاقة‬
 Power Electronic Control ‫كلية تكنولوجيا الصناعة والطاقة‬

• As EV and HEV propulsion, an induction motor drive is usually fed with a DC source (e.g., battery, fuel
cell), which has approximately constant terminal voltage. Thus, a variable frequency and variable-
voltage DC/AC inverter is needed to feed the induction motor. A general DC/AC inverter is constituted
by power electronic switches and power diodes.
• The commonly used topology of a DC/AC inverter is shown in Figure, which has three legs (S1 and S4,
S3 and S6, and S5 and S2), feeding phases a, b, and c of the induction motor.
• When switches S1, S3, and S5 are closed, S4, S6, and S2 are opened, and phases a, b, and c are supplied
with a positive voltage (Vd/2). Similarly, when S1, S3, and S5 are opened and S4, S6, and S2 are closed,
phases a, b, and c are supplied with a negative voltage. All the diodes provide a path for the reverse
current of each phase.
 Power Electronic Control ‫كلية تكنولوجيا الصناعة والطاقة‬

• For constant volt/hertz control of an induction motor, sinusoidal pulse width modulation (PWM) is used
exclusively. Three-phase reference voltages Va, Vb, and Vc of variable amplitudes Aa, Ab, and Ac are
compared with a common isosceles triangular carrier wave Vtr of a fixed amplitude Am, as shown in
Figure.
• The outputs of comparators 1, 2, and 3 form the control signals for the three legs of the inverter. When
the sinusoidal reference voltages Va, Vb, and Vc at a time t are greater than the triangular waved
voltage, turn-on signals are sent to the switches S1, S3, and S5 and turn-off signals to S4, S6, and S2.
Thus, the three phases of the induction motor have a positive voltage.
• On the other hand, when the reference sinusoidal voltage is smaller than the triangular wave voltage,
turn-on signals are sent to switches S1, S3, and S5 and turn-off signals to S4, S6, and S2. The three
phases of the induction motor then have a negative voltage.
• The frequency of the fundamental component of the motor terminal voltage is the same as that of the
reference sinusoidal voltage. Hence, the frequency of the motor voltage can be changed by changing
the frequency of the reference voltage.
‫كلية تكنولوجيا الصناعة والطاقة‬
‫كلية تكنولوجيا الصناعة والطاقة‬
‫كلية تكنولوجيا الصناعة والطاقة‬
 Sensors ‫كلية تكنولوجيا الصناعة والطاقة‬

• In order to carry out motor/generator switching accurately, the power/control electronics need to know
the condition and exact speed and position of the motor. The speed and position information is
supplied by one or more sensors mounted on the casing in conjunction with a reluctor ring.
• The system uses 30 sensor coils and an eight-lobe reluctor ring. The output signal changes as a lobe
approaches the coils and this is recognized by the control unit.
• The coils are connected in series and consist of a primary and two secondary windings around an iron
core. The separate windings produce different signals because as the reluctor moves it causes the signal
in each secondary winding to be amplified.
• The position of the rotor can therefore be determined with high accuracy using the amplitudes of the
signals. The frequency of the signal gives the rotational speed.
• A drive motor temperature sensor is usually used and it also sends signals to the electric drive control
unit. Typically, the power of the drive motor is restricted at temperatures above about 150°C, and in
some cases above 180°C it may even prevent the drive from being used to protect it against
overheating. The sender is normally a negative temperature coefficient (NTC) thermistor.
‫كلية تكنولوجيا الصناعة والطاقة‬
 Types of battery ‫كلية تكنولوجيا الصناعة والطاقة‬

Lead–acid batteries (Pb–Pb02)

• Even after about 150 years of development and much promising research into other techniques of
energy storage, the lead–acid battery is still the best choice for low-voltage motor vehicle use. This is
particularly so when cost and energy density are taken into account.
• Incremental changes over the years have made the sealed and maintenance-free battery now in
common use very reliable and long lasting. This may not always appear to be the case to some end-
users, but note that quality is often related to the price the customer pays. Many bottom-of-the-range
cheap batteries, with a 12-month guarantee, will last for 13 months!
• The basic construction of a nominal 12 V lead–acid battery consists of six cells connected in series. Each
cell, producing about 2 V, is housed in an individual compartment within a polypropylene, or similar,
case.
• The active material is held in grids or baskets to form the positive and negative plates. Separators made
from a micro-porous plastic insulate these plates from each other.
‫كلية تكنولوجيا الصناعة والطاقة‬
 Types of battery ‫كلية تكنولوجيا الصناعة والطاقة‬

Alkaline (Ni–Cad, Ni–Fe and Ni–MH)

• The main components of the nickel–cadmium (Ni–Cad or NiCad) cell for vehicle use are as follows:
• Positive plate – nickel hydrate (NiOOH)
• Negative plate – cadmium (Cd)
• Electrolyte – potassium hydroxide (KOH) and water (H2O).
• The process of charging involves the oxygen moving from the negative plate to the positive plate, and
the reverse when discharging.
• When fully charged, the negative plate becomes pure cadmium and the positive plate becomes nickel
hydrate. A chemical equation to represent this reaction is given next,
 Types of battery ‫كلية تكنولوجيا الصناعة والطاقة‬

Alkaline (Ni–Cad, Ni–Fe and Ni–MH)

• The 2H2O is actually given off as hydrogen (H) and oxygen (O2) because gassing takes place all the time
during charge. It is this use of water by the cells that indicates they are operating, as will have been
noted from the equation. The electrolyte does not change during the reaction. This means that a
relative density reading will not indicate the state of charge.
• NiCad batteries do not suffer from over-charging because once the cadmium oxide has changed to
cadmium, no further reaction can take place.
• Nickel–metal hydride (Ni–MH or NiMH) batteries are used by some electric vehicles and have proved to
be very effective. Toyota in particular has developed these batteries. The components of NiMH
batteries include a cathode of nickel–hydroxide, an anode of hydrogen absorbing alloys and a
potassium hydroxide (KOH) electrolyte. The energy density of NiMH is more than double that of a lead–
acid battery but less than lithium-ion batteries.
 Types of battery ‫كلية تكنولوجيا الصناعة والطاقة‬

Lithium-ion (Li-ion)
• Lithium-ion technology is becoming the battery technology of choice, but it still has plenty of potential
to offer. Today’s batteries have an energy density of up to 140 Wh/kg or more in some cases, but have
the potential to go as high as 280 Wh/kg. Much research in cell optimization is taking place to create a
battery with a higher energy density and increased range. Lithium-ion technology is currently
considered the safest.
• The Li-ion battery works as follows. A negative pole (anode) and a positive pole (cathode) are part of
the individual cells of a lithium-ion battery together with the electrolyte and a separator. The anode is a
graphite structure and the cathode is layered metal oxide. Lithium-ions are deposited between these
layers. When the battery is charging, the lithium-ions move from the anode to the cathode and take on
electrons.
• The number of ions therefore determines the energy density. When the battery is discharging, the
lithium-ions release the electrons to the anode, and move back to the cathode.
‫كلية تكنولوجيا الصناعة والطاقة‬
‫‪Field orientation Control‬‬ ‫كلية تكنولوجيا الصناعة والطاقة‬
 Electronically commutated motor ‫كلية تكنولوجيا الصناعة والطاقة‬

• The electronically commutated motor (ECM) is, in effect, half way between an AC and a DC motor. Its
principle is very similar to the synchronous motor above, except the rotor contains permanent magnets
and hence no slip rings. It is sometimes known as a brushless motor. The rotor operates a sensor, which
provides feedback to the control and power electronics.
• This control system produces a rotating field, the frequency of which determines motor speed. When
used as a drive motor, a gearbox is needed to ensure sufficient speed of the motor is maintained
because of its particular torque characteristics.
• Some schools of thought suggest that if the motor is supplied with square-wave pulses it is DC, and if
supplied with sine-wave pulses then it is AC.
• These motors are also described as brushless DC motors (BLDC) and they are effectively AC motors
because the current through it alternates. However, because the supply frequency is variable, has to be
derived from DC and its speed/torque characteristics are similar to a brushed DC motor, it is called a DC
motor.
• It can also be called a self-synchronous AC motor, a variable frequency synchronous motor, a permanent
magnet synchronous motor, or an electronically commutated motor (ECM). The rotor is a permanent
magnet and the current flow through the coil determines the polarity of the stator. If switched in
sequence and timed accordingly, the momentum of the rotor will keep it moving as the stator polarity is
changed. Changing the switching timing can also make the rotor reverse.
 Electronically commutated motor ‫كلية تكنولوجيا الصناعة والطاقة‬

• The switching must be synchronized with the rotor position and this is done
by using sensors, Hall Effect in many cases, to determine the rotor position
and speed. If three coils or phases are used, as shown next, then finer
control is possible as well as greater speed, smoother operation and
increased torque. Torque reduces as speed increases because of back EMF.
Maximum speed is limited to the point where the back EMF equals the
supply voltage.
‫كلية تكنولوجيا الصناعة والطاقة‬
 ‫كلية تكنولوجيا الصناعة والطاقة‬

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