In every industry there are processes some form that require adjustment for normal operation. Such adjustments are usually accomplished with variable speed drive and it consists of
- Power Converter
- Electric Motor
Controller: The controller generates PWM signal to the converter & hence forms the heart of the Variable speed system.
Power Converter: It controls the power flow from an AC supply to the motor by appropriate control of power semiconductor switches (part of power Converter).
Electric Motor: It is connected directly/indirectly to the load.
DSPIC30F Family of Microcontrollers
- Introduction to dsPIC Microcontrollers
- dsPIC architecture
- dsPIC Pin details
- Peripherals details
- How to Program this controller datails
DSPIC Pin details
DSPIC Microcontrollers overview
- I/O Ports
- Input Capture Module
- Output Compare Module
- Quadrature Encoder Interface (QEI)
- 10-bit A/D Converter
- 12-bit A/D Converter
- UART Module
- SPITM Module
- I2CTM Module
- Data Converter Interface (DCI) Module
- CAN Module
High Performance Modified RISC CPU
- Modified Harvard architecture
- C compiler optimized instruction set architecture With flexible addressing modes
- 84 base instructions
- 24-bit wide instructions, 16-bit wide data path
- 48 Kbytes on-chip Flash program space (16K Instruction words)
- 2 Kbytes of on-chip data RAM
- 1 Kbytes of non-volatile data EEPROM
- Up to 30 MIPs operation:
- DC to 40 MHz external clock input
- 4 MHz-10 MHz oscillators input with
- PLL active (4x, 8x, 16x)
- 30 interrupt sources
- 3 external interrupt sources
- 8 user selectable priority levels for each Interrupt source
- 4 processor trap sources
- 16 x 16-bit working register array
DSP Engine Features
- Dual data fetch
- Accumulator writes back for DSP operations
- Modulo and Bit-Reversed Addressing modes
- Two, 40-bit wide accumulators with optional saturation logic
- 17-bit x 17-bit single cycle hardware fractional/ integer multiplier
- All DSP instructions single cycle
- ± 16-bit single cycle shift
Motor Control PWM Module Features
- 6 PWM output channels
- Complementary or Independent Output Mode
- Edge and Center Aligned modes
- 3 duty cycle generators
- Dedicated time base
A Switched Reluctance or Variable Reluctance Motor does not contain any permanent magnets. The stator is similar to a brushless dc motor. However, the rotor consists only of iron laminates. The iron rotor is attracted to the energized stator pole. The polarity of the stator pole does not matter. Torque is produced as a result of the attraction between the electromagnet and the iron rotor.
Cross Sectional View of SR Motor
The rotor forms a magnetic circuit with the energized stator pole. The reluctance of a magnetic circuit is the magnetic equivalents to the resistance of an electric circuit. The reluctance of the magnetic circuit decreases as the rotor aligns with the stator pole. When the rotor is in line with the stator the gap between the rotor and stator is very small. At this point the reluctance is at a minimum. This is where the name “Switched Reluctance” comes from.
Features of Our Module
Our module has the following features
- Various test points to check waveforms at different stages of operation.
- Flexibility to work with different controller modules developed by us.
- Necessary protections are provided through fuses. A separate protection circuit for input over current faults.
- Power supply to the Eddy Current load coil is also provided from the module.
- Required connectors are provided for motor input supply connection and feedback signal connection.
- Rated Voltage = 50Vdc
- Current = 4.5 Amp
- Speed = 4000 RPM
- Phase = 4 Phase (8/6 Pole)
Block Diagram for SRM Power module
The block diagram of SRM Driver Module is shown in figure. It consist of a
- Bridge Rectifier
- IGBT Driver
- Opto- Isolator and Gate driver
- Current Sensor
- SRM Hall Sensor
Opto isolator & Gate Driver
The Opto Isolator placed inside the module is to isolate the high impedance side from low impedance side. Hence the optoisolator is placed to isolate the PWM pulses from the Micro-4011 Trainer to the driver in power module. The driver provides the PWM signal to the switches and drives them.
The output sensing circuits measure motor winding currents. The current values measured are scaled to analog voltages (3.5 A/V). The sensor used for current sensing works on the principle of Hall Effect, so those sensors are called as Hall Effect Transducer. Hall Effect Transducer output current depends upon the transducer primary and secondary windings ratio. The turn ratio depends on the ratio of primary turn to the ratio of secondary turn. Current Transducer Schematic diagram is as shown in figure.
SRM Hall Sensor
The rotor position is sensed using a Hall Sensor placed inside the motor. The rotor position is sensed once in 15??i.e the rotor position changes for each 15?.
Exp: Speed control of Switched Reluctance Motor
To control the speed of Switched Reluctance Motor using Micro-4011 trainer and SRM power module.
- Power Module
- Switched Reluctance Motor
- Micro-4011 trainer
- Patch Chords
- 20 Pin FRC cable
- (0-30) Regulated power supply
- Connect the 2-pin power adaptor of the Micro-4011 trainer to the supply.
- Connect the power module to the P N power supply.
- Connect the 20 pin FRC cable one end to 10 pin FRC connector in Micro-4011 trainer and the other end to “IGBT- PWM INPUTS” of the power module.
- Connect the 20 pin FRC cable one end to 20 pin connector in Micro-4011 trainer and the other end to “FEEDBACK SIGNALS” of the power module.
- Connect the motor feedback to the motor feedback connector provided in the SRM power module.
- Connect the motor power output terminal of power module to the power input terminal of Switched Reluctance Motor.
- Connect the (0-30) V DC power supply to the Eddy Current coil terminals.
- Verify the connections as per the connection procedure and connection diagram.
- Switch ON the Micro-4011 trainer.
- Switch ON the power ON/OFF switch in the SRM Power Module.
- Check whether shut down LED "SD" glows or not. If 'SD' LED glows press the Reset switch, the LED gets OFF.
- Switch on the ac supply external source and gradually increase the voltage up to 300 V (DC link voltage) using 1 ph variac.
- In the micro 4011 we are provide the INC & DEC key provided.
- Digital LCD also provided in the micro 4011 set speed and actual speed displaying.
- Select the motor open loops are closed loop using INC are DEC.