AN1524 Freescale Semiconductor / Motorola, AN1524 Datasheet - Page 2

• Manufacturer Part Number: AN1524
• Description: AC Motor Drive Using Integrated Power Stage
• Manufacturer: Freescale Semiconductor / Motorola

three phase rectifier and a three phase inverter. The three
phase rectifier converts a three phase AC power source into
a DC supply. A single phase power source may also be
connected to any two of the three inputs. Electrolytic
capacitors are used to provide energy storage for the DC
supply.
recovery diodes is used to drive the motor. Three phase AC
is then generated by using sine wave pulse width modulation.
The voltage and frequency of the AC output can be easily
controlled using an embedded microcontroller unit. The most
common constant V/F (volts per hertz) drives provide sine
frequencies of 1 to 120 Hz and voltages of 0 to 240 VAC or 480
VAC. The three phase inverter is very flexible and can also be
used for most three phase motors and modulation or
commutation schemes. This includes brushless DC motors.
capable of generating, a dynamic brake circuit is often used.
When the speed command is reduced in an AC drive, the
motor will regenerate. The real part of the three phase power
flows from the motor to the inverter. This results in current
flowing from the inverter into the DC buss capacitors. Because
this energy cannot flow back into the AC supply it must be
stored in the capacitors or dissipated. If too much energy is
AN1524
The power semiconductors for an AC drive consist of a
A three phase inverter consisting of six IGBTs and six soft
Because AC motors under sine wave excitation are also
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Freescale Semiconductor, Inc.
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For More Information On This Product,
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Figure 2. Integrated Power Stage Schematic
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pumped into the capacitors the voltage will rise to
unacceptable levels. A dynamic brake resistor and a seventh
IGBT are often used to dissipate this energy. Because large
resistors used for dynamic braking are inductive, a clamp
diode is used to limit the transistor voltage during turnoff.
AC drive system. Using single transistor discrete packages is
very cumbersome. Often a rectifier module and IGBT six pack
is used with a discrete transistor for the brake. This simplifies
matters a little, reducing the number of components that must
be mounted to a heatsink and soldered to three.
solution for small motor drives. A schematic of the Integrated
Power Stage is shown in Figure 2 and the module is illustrated
in Figure 3. These modules contain all the power electronics
for an AC drive. By combining all the power devices into a
single package mounting use is greatly simplified. A single
module is fewer parts than two modules. This should reduce
manufacturing cost and improve reliability. The Integrated
Power Stage also contains a 1% sense resistor and a
temperature sense diode. These components can be used to
provide status and control functions as well as protection
features.
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There are a total of 20 power semiconductor devices in this
The “Integrated Power Stage” Module is a comprehensive
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INTEGRATED POWER STAGE MODULE
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MOTOROLA
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