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DESCRIPTION

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

☞Controller

☞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 architecture

dspic-architecture-for-srm-motor

DSPIC Pin details

dspic-pin-details-for-srm-motor

DSPIC Microcontrollers overview

dspic-microcontrollers-overview-for-srm-motor 

Peripheral details

☞I/O Ports

☞Timers

☞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

☞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

CPU (Cond.,)

☞Up to 30 MIPs operation:

☞DC to 40 MHz external clock input

☞4 MHz-10 MHz oscillator 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

BLDC MOTOR

Brushless Permanent Magnet Motors, Permanent Magnet AC motors, Permanent Magnet Synchronous Motors etc. The confusion arises because a brushless dc motor does not directly operate of a dc voltage source. However, as we shall see, the basic principle of operation is similar to a dc motor.

A Brushless DC motor has a rotor with permanent magnets and a stator with windings. It is essentially a dc motor turned inside out. The brushes and commutator have been eliminated and the windings are connected to the control electronics. The control electronics replace the function of the commutator and energize the proper winding. The energized stator winding leads the rotor magnet, and switches just as the rotor aligns with the stator. There are no sparks, which is one advantage of the BLDC motor. The brushes of a dc motor have several limitations; brush life, brush residue, maximum speed, and electrical noise.

BLDC Motors are potentially cleaner, faster, more efficient, less noisy and more reliable. However, BLDC motors require electronic control.

BLDC OPERATION

A permanent Magnet AC motor, which has a trapezoidal back emf, is referred to as brushless DC motor (BLDC). The BLDC drive system is based on the feedback of rotor system at fixed points for commutation of the phase currents.

The BLDC motor requires quasi-rectangle shaped currents fed into the machine. Alternatively, the voltage may be applied to the motor every 120°, with current limit to hold the current within motor capabilities. Because the phase currents are excited in synchronism with the constant part of the back emf, constant torque is generated. The electromagnetic torque of the BLDC motor is related to the product of phase, back emf and current. The back emf in each phase are trapezoidal in shape and are displaced by 120 electrical degree with respect to each other in 3 phase machine. A rectangle current pulse is injected into each phase so that current coincides with the ack emf waveform; hence the motor develops an almost constant toque. bldc-operation

BLDC HALL SENSOR

Hall Effect sensor provides the portion of information needed to synchronize the motor excitation with rotor position in order to produce constant torque. It detects the change in magnetic field. The rotor magnets are used as triggers to the Hall Sensor. A signal conditioning circuit integrated within the Hall switch provides a TTL-compatible pulse with sharp edges. Three Hall Sensors placed 120° apart, are mounted on the stator frame. The Hall Sensor digital signals are used to sense the rotor

position 

position

bldc-hall-sensors

MOTOR SPECIFICATIONS

Power 1HP

Voltage 24 v

Speed 2400 RPM

Current 31.65 amps

FEATURES

☞Trapezoidal three phase back emf waveform

☞Hall effect sensors, Encoder and index feedback.

☞Temperature sensor mounted in motor winding

☞Additional Encoder interfacing facility

☞Motor and feedback connector, counterpart plugs optional.

☞Malt Block paint finish

EXPERIMENTAL SECTION

AIM

To study the open loop and closed loop speed control of BLDC Motor by using DSPIC 4011 microcontroller and IPM module.

EQUIPMENTS REQUIRED

☞IPM Power Module

DSPIC 4011 microcontroller

☞BLDC Motor

☞Cables -24 pin DB to 20 pin header. -Feedback connector cable (9 pin D cable).

CONNECTION PROCEDURE

☞Connect the 24 pin cable from the DSPIC 4011 microcontroller to power module (IPM) along with the Hall signal conditional cable.

☞Connect the feedback cable between motor and Hall signal conditioning card.

☞Connect the motor terminals R, Y, B to the in “IPM Power Module”

EXPERIMENTAL PROCEDURE

☞Verify the connections as per the connection procedure and Wiring Diagram.

☞Switch ON the DSPIC 4011 microcontroller trainer kit.

☞Power ON the IPM Power Module

☞Check whether shut down LED "SD" glows or not. If 'SD' LED glows, press the Reset switch, the LED gets OFF.

OPEN LOOP CONTROL

☞Verify the PWM waveform and Hall sensor output which are terminated in the power module.

☞After ensuring all the connection, apply the input voltage to the IPM power module DC rail voltage 30V. which is shown in the power module voltmeter.

☞Select mode forward or reverse .Select the open loop mode

☞Now the motor starts to rotate in the set speed.

☞By using the switches increment (S1) and decrement (S2) set the speed of the motor.

☞The actual speed of the motor will be displayed in the LCD.

☞To measure the load current of the motor, externally connect one DC ammeter in series with any one DC input side.

CLOSED LOOP CONTROL

☞Verify the PWM waveform and Hall sensor output which are terminated in the power module.

☞After ensuring all the connection, apply the input voltage to the IPM power module DC rail voltage (30V), which is shown in the power module voltmeter.

☞Select mode forward or reverse .Select the closed loop mode

☞Now the motor starts to rotate in the set speed.

☞By using the switches increment (S2) and decrement (S3) set the speed of the motor.

☞The actual speed of the motor will be displayed in the LCD.

☞Now apply the load to the motor at rated current rating and analyze the performance of the closed loop control.

☞The actual speed of the motor remains same as set speed after applying the load in close loop condition

☞To measure the load current of the motor, externally connect one DC ammeter in series with any one DC input side.