303
Electric Vehicles
In case of a shunt wound DC motor, the torque almost remains constant as
the speed increases until the maximum point is reached. In general, starting
torque is of 125–200% full load torque. Efficient thyristor or transistor controls capable of controlling both field and armature current by turning it
on or off at high speed makes the efficient use of shunt motors for EVs. The
distinct advantage of shunt motors is the ability to reverse the motor by only
reversing the relative low-current field connections, instead of reversing the
full armature current like the series wound motor. As increased use of electronic controls improves the efficiency and controllability of shunt wound
motors, their use has spread although series motors still have a place in some
low-cost vehicles.
Combining the series and shunt field coils in a motor having a compound
wound field provides a possibility to obtain a wide range of characteristics
between the extremes of the series and shunt wound motors. Two arrangements can be made; keeping the shunt long or short, with the series field
supplementing the shunt field. This cumulative compounding can make
a way to use compound wound motors to act as a series like motor or a
shunt like motor, getting both advantages. The characteristics can therefore
to some extent be tailored to the requirement of a particular vehicle design
(Wakefield 1998).
10.3.1.4 Separately Excited DC Motor
Use of power electronics with the capability of controlling higher current
and relatively higher voltages in recent years makes the DC motor’s armature current and field current to be controlled independently by separate
excitation. This makes the possibility of achieving any required variable
combination of series, shunt, and compound characteristics. But the major
drawback lies in sending the feedback of rotor speed to the electronic power
control system, which necessitates the use of commutator and brush to carry
the armature current. Hence the motor speed is limited and causes wear and
consequent unreliability.
DC motor drives have been widely used in applications requiring adjustable speed, good speed regulation, frequent starting, braking, and reversing.
Various DC motor drives have been widely applied to different electric traction
applications due to the simplicity, low cost of control systems, and the maturity
of the technology. This will remain in service at least in low cost EV markets.
10.3.1.5 AC Motor Drives
Commutatorless motor drives offer a number of advantages over conventional DC commutator motor drives for the electric propulsion of hybrid
EVs. AC induction motor drives have additional advantages such as being
lightweight in nature, small volume, low cost, and high efficiency. Generally
Electric Vehicles
In case of a shunt wound DC motor, the torque almost remains constant as
the speed increases until the maximum point is reached. In general, starting
torque is of 125–200% full load torque. Efficient thyristor or transistor controls capable of controlling both field and armature current by turning it
on or off at high speed makes the efficient use of shunt motors for EVs. The
distinct advantage of shunt motors is the ability to reverse the motor by only
reversing the relative low-current field connections, instead of reversing the
full armature current like the series wound motor. As increased use of electronic controls improves the efficiency and controllability of shunt wound
motors, their use has spread although series motors still have a place in some
low-cost vehicles.
Combining the series and shunt field coils in a motor having a compound
wound field provides a possibility to obtain a wide range of characteristics
between the extremes of the series and shunt wound motors. Two arrangements can be made; keeping the shunt long or short, with the series field
supplementing the shunt field. This cumulative compounding can make
a way to use compound wound motors to act as a series like motor or a
shunt like motor, getting both advantages. The characteristics can therefore
to some extent be tailored to the requirement of a particular vehicle design
(Wakefield 1998).
10.3.1.4 Separately Excited DC Motor
Use of power electronics with the capability of controlling higher current
and relatively higher voltages in recent years makes the DC motor’s armature current and field current to be controlled independently by separate
excitation. This makes the possibility of achieving any required variable
combination of series, shunt, and compound characteristics. But the major
drawback lies in sending the feedback of rotor speed to the electronic power
control system, which necessitates the use of commutator and brush to carry
the armature current. Hence the motor speed is limited and causes wear and
consequent unreliability.
DC motor drives have been widely used in applications requiring adjustable speed, good speed regulation, frequent starting, braking, and reversing.
Various DC motor drives have been widely applied to different electric traction
applications due to the simplicity, low cost of control systems, and the maturity
of the technology. This will remain in service at least in low cost EV markets.
10.3.1.5 AC Motor Drives
Commutatorless motor drives offer a number of advantages over conventional DC commutator motor drives for the electric propulsion of hybrid
EVs. AC induction motor drives have additional advantages such as being
lightweight in nature, small volume, low cost, and high efficiency. Generally