The air gap flux and the rotor speed are detected by processing the signal obtained from the summation of the stator phase voltages, Vs3. The DSP performs the integration of the third harmonic voltage signal to derive the third harmonic flux. In order to detect the rotor speed the signal Vs3 is processed by a switched capacitor band-pass filter (SCF), whose central frequency can be tuned over a wide range (from about 20 Hz to 4 kHz). The output of the filter is a variable amplitude sinusoidal wave. This wave has the same frequency as the rotor slot ripple . Two options are to detect the frequency of the SCF output signal: a Phase Locked Loop or a frequency to voltage converter (FVC).
5.step 3.2. Career Programmable Entrance Arrays (FPGA)
A remarkable application of DSPs otherwise FPGAs is the sensorless handle for high-speed apps based on the execution of PWM manage techniques, which are categorized since the unipolar and bipolar strategies [24,51]. According to PWM method used the manage program could potentially cause good commutation decrease when you look at the high-speed apps because PWM changing in addition to inverter commutation can’t be complete separately. When your commutation quick is actually synchronized for the stop of your PWM modifying period most useful commutation occurs which have one reduce. But since the commutating instant hinges on the fresh new rotor status it doesn’t basically coincide on the prevent of PWM period and you can unwelcome commutation decelerate is actually delivered. This matter might be overcome of the controlling the voltage and frequency independently from the DC hook current manage scheme. It control is adopted playing with an excellent DSP otherwise FPGA built high speed sensorless manage setting .
Normal high-speed programs where PWM techniques can be applied try digital clips drive (DVD) spindle options, which will be implemented using a FPGA, including the Altera Flex EPF6024AQC240-3 . Brand new controller includes several head bits: the brand new PWM age group routine together with fuel tool manage circuit. Figure 23 suggests the machine, using its a great FPGA, a beneficial BLDC motor, while the associated reference and you will feeling circuits . Just critical voltages away from about three phase are sampled and fed to the the new FPGA controller in order to estimate the newest commutation instants. The program causes tall decrease in conduction losings and you will energy use, that’s somewhat very important to brief fuel BLDCM drives running on power supply and you can/otherwise that have limited dissipation area.
5.3.step 3. Microprocessors (MP)
A low-prices sensorless manage system getting BLDC cars is going to be adopted in the event the rotor standing data is derived by the filtering singular system-terminal-current, which results in high losing portion amount of the sensing circuit. Because shown inside Contour nine , only two of the three condition-windings is excited immediately, as well as the third phase are discover inside transition symptoms anywhere between the positive and you can negative flat segments of your own back-EMF . Ergo, all the motor critical voltages comes with the back-EMF pointers which you can use to obtain this new commutation instants.
Cost saving is further increased by coupling the position sensing circuit with a single-chip https://datingranking.net/nl/snapsext-overzicht/ microprocessor or DSP for speed control. Figure 24 shows a block diagram of the position detection circuit based on sensing all three motor terminal voltages for a BLDC motor. Each of the motor terminal voltages, referred to as the negative DC bus rail VA‘, VB‘ and VC‘ are fed into a filter through a voltage divider of a resistor network. This removes the DC component and high frequency contents that result from the PWM operation. The phase information is extracted from the back-EMF. The correction is based on measuring the elapsed time between the last two zero-crossing instants and converting it to frequency. This operation is achieved when the filtered voltage, VA”, is passed to a comparator to detect these zero-crossing instants, which are further sent to a microprocessor for phase-delay correction and generation of commutation signals. The microprocessor produces gate control signals for the inverter and may perform closed speed control with the motor speed information measured by the frequency of the detected signals .