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When I was doing my PhD in motor design of reluctance machines with flux assistance (switched reluctance machines and flux switching machines with magnets and/or permanently energised coils) my supervisor was doing research on the field of sensorless control (it wasn't the area of my research but it got me thinking about it all).
A completely sensor-less control would be completely open-loop, which isn't reliable with some motors like PMSMs. Even if you knew the switching instants for one ideal case, too many "random" variables could influence the system (just think of the initial position), so that those firing instants could be inappropriate for other situations.
You can build it all in MagNet using the circuit position controlled switch. You will have to use motion analysis in order to use the position controlled switches. You can also use the back EMF information to find what the optimal position for the rotor should be with respect to the stator field. The nice thing about motion is that even if you do not have the rotor in the proper position you can set the reference at start up.
For AM & FM radio & some data communications adding the QP filter make sense. Now that broadband, wifi, data communications of all sizes & flavours exist - any peak noise is very likely to cause interuptions & loss of integrity of data - all systems are being 'cost reduced' ensuring that they will be more susceptible to noise.
Having lead design efforts for very sensitive instrumentation with high frequency A/D converters with greater than 20-bits of resolution my viewpoint is mainly concerned about the noise in the regulated supply output. In these designs fairly typical 50-mV peak-to-peak noise is totally unacceptable and some customers cannot stand 1-uVrms noise at certain frequencies.
Coming from a signal processing and communications theory background, but with some experience in power design, I can't resist the urge to chime in with a few remarks. There are many engineering methods to deal with sources of interference, including noise from switching converters, and spread spectrum techniques are simply one more tool that may be applied to achieve a desired level of performance.
The way around all the disadvantages is to use a doubly fed induction generator (DFIG). In addition to the stator connection to the load, the wound rotor is provided with a varying AC field whose frequency is tightly controlled through smart electronics so that a relatively fixed controllable output voltage and frequency can be achieved despite the varying speed of the prime mover and the load.
Hazardous area classification has three basic components:
Class (1,2) : Type of combustible material (Gas or Dust)
Div (I, II) : Probability of combustible material being present
Gas Group (A,B,C,D): most combustible to least combustible (amount of energy required to ignite the gas)
Often, in automation, engineers will use a PLC or DCS with standard I/O, valves, servos, photo-eyes, VFDs, RTDs, etc to accomplish this task. Control engineering falls under the same umbrella in that you are automating a process such as controlling the focus on a camera or maintaining the speed of a car with a gas pedal.
We used four huge 5KV motors and VFDs at the coal mine compared to a single 0.75 HP 480 VAC VFD at the bakery, and startups/shutdowns were order of magnitudes different, but the time frame was immaterial to what the controls had to do and the techniques I applied to do the job.
The PPE (Personal Protective Equipment) requirements to work on live electrical equipment is making doing commissioning, startup, and tuning of electrical control systems awkward and cumbersome. We are at a stage where the use of PPE is now required but practice has not caught up with the requirements. While many are resisting this change, it seems inevitable that we will need to wear proper PPE equipment when working on any control panel with exposed voltages of 50 volts or more.
A system I have just completed was 24 containers + 3 buildings for storage with 76 conveyors, 3 drop-off and 3 loading points. Connection to ERP system and weigh scales to weigh trucks and send them to the correct bay. Local HMI on each bay ensured correct lorry goes to correct bay. Main conveyor runs are automatically selected. Manual option to run all conveyors to move grain around.
Gozuk Service Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.


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