AN1524 Freescale Semiconductor / Motorola, AN1524 Datasheet - Page 8

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

programmed using a Data I/O 2900 programmer. The actual
ABLE code is included in Appendix III.
logic equations, recompiling the ABLE code and programming
a new PLD. In an AC motor drive system many of the functions
are a combination of hardware and microprocessor software.
The PLD provides the flexibility of being able to easily change
the hardware to implement new functions.
signals under overcurrent conditions. This was intentionally
done to enable easy setup and testing of the drive system.
Once the system is setup and running, an overcurrent latch
may be added by changing the PLD. An overcurrent latch is
very sensitive to noise and may result in too many false trips
in some systems.
automatically when the over voltage comparator detects an
over voltage. The micro should monitor the regeneration
current to protect the inverter, brake transistor and brake
resistor.
mains. This topology is very common in low cost AC drives.
The microprocessor is grounded on the negative supply of the
high voltage DC buss. Thus, the micro and associated
circuitry are hot and must be isolated from user controls and
serial interfaces in final product form.
power supplies and oscilloscopes. This prevents a shock from
touching any single point in the circuit. This does not, however,
prevent shocks when touching two or more points in the
circuit. If absolutely necessary, one point in the circuit (the
micro ground for example) may be earth grounded. However,
AN1524
Additional functions may be implemented by changing the
The standard PLD does not directly disable the PWM
The brake transistor can be configured to turn on
The motor drive demo is not electrically isolated from the AC
In the laboratory it is safest to isolate the AC supply, auxiliary
8
ISOLATED THREE PHASE
AC POWER SUPPLY
(SEE TEXT)
Freescale Semiconductor, Inc.
100 mA
For More Information On This Product,
+18 V
IPS AC MOTOR DRIVE
Figure 11. Laboratory Set–up Block Diagram
MICROPROCESSOR
DEMO BOARD
AC CONTROL
BOARD
Go to: www.freescale.com
1 AMP
+ 5 V
desirable to invert the PWM polarities. This can easily be
accomplished by simply changing the logic equations and
moving jumper J1. Also included in Appendix III are ABLE
examples of using the brake for overvoltage and inverted
inputs.
Laboratory Setup
laboratory. The high voltage levels present in any AC drive
system represent a serious shock hazard. The demo board
should only be used by engineers and technicians who are
experienced in power electronics.
supply, the IPS AC Motor Drive demo board, an AC induction
motor, a dynamometer or motor load, a microprocessor board
and isolated lab supplies for +18 V and +5 V. A block diagram
of the lab setup is shown in Figure 11.
this establishes all high voltage nodes at dangerously high
voltages.
isolation transformer and a variable transformer (variac). A
schematic of the recommended AC power source is shown in
Figure 12. Fast semiconductor grade fuses should be used
directly up line of the AC drive. The transformer should be
fused with slower fuses to prevent blowing a fuse when
energizing the transformer. The demo board contains
thermistors to prevent excessive inrush current. However, it is
advisable to use a variac when first powering up the system.
When used with a different microprocessor, it may be
The demo board is intended to be used only in a power
A complete laboratory setup consists of an isolated AC
An isolated AC power supply can be constructed using an
AC MOTOR
MOTOR
LOAD
MOTOROLA