Environmental Engineering Reference
In-Depth Information
Chapter 6
Power electronics for ac drives
Power electronics and its control fall within what is known as 'inner-loop' control
of the hybrid ac drive system. Starting with solid state, or brushless, commutators,
for permanent magnet electric machines in the 1970s, the techniques of solid state
motor control have been applied to industrial induction machines in the form of
adjustable speed drives (nearly 90% of all electric machines produced and sold are
induction machines) and recently to interior permanent magnet and reluctance
machines for hybrid propulsion. Without the advancements and miniaturization
efforts of the semiconductor community, the hybrid vehicle would not be market
ready.
As the highest cost component of the hybrid propulsion system, with the possible
exception of the vehicle battery, the power electronics represents one of the most
complex power processing elements in the vehicle. In this chapter the various types
of semiconductor devices are summarized along with their applicability for use as in-
vehicle power control. The assessment of power electronics for ac drive systems then
continues with discussion of various modulation techniques, thermal design and
reliability considerations. Modulation techniques are important for many reasons.
Most of the present modulation methods are capable of synthesizing a clean sinu-
soidal ac waveform from the vehicles on-board energy storage system (ESS), but not
all do so with equal efficiency, noise emissions or dc voltage utilization.
Integration of power electronic systems today is at the stage where a single
integrated power module consisting of a full active bridge of power semiconductors,
integrated gate drivers, and fault detection and reporting logic is available off the
shelf. At higher powers (
>
50 kW), the power electronics may consist of individual
phase leg modules. At low powers (
<
1.5 kW), the complete power electronic stage
and microcontroller are all integrated into a single smart power brick. The Interna-
tional Rectifier, Plug-N-Drive series (IRAMS10UP60A), is a 10 A, 600 V, 3-phase
motor controller all fully integrated into an SIPI and capable of 20 kHz pulse width
modulation (PWM) [1]. The Plug-N-Drive component is an example of an Intelligent
Power Electronic Module (IPEM). The IR IPEM is chip and wire fabricated on
insulated metal substrate technology, IMST, with 600 V non-punch-through (NPT)
insulated gate bipolar transistors (IGBTs) that are matched with ultra-soft recovery
anti-parallel diodes for low electromagnetic interference (EMI). Figure 6.1 illustrates
in schematic form the layout of an IPEM.
