Modern industrial electronics and control devices - relays, contactors, DC and AC motors; stepper motors; three-phase power and its control, optoelectronic devices, SCRs, Triacs and other thyristor devices; PLCs and ladder diagrams; introduction to control systems.
In this lab we had to construct a basic motor starter and then add forward and reverse capabilities to the motor starter. The relays used were DPDT, double pole double throw. We began by first making a basic motor starter, where a momentary start button is pushed, then a control relay is powered on as is the motor, finally the CR contacts switch from normal position keeping the motor and relay on until the stop button is pushed. The reason this works is because once the control relay is on the CR contacts switched from normally open to closed, this contact bypassed the start switch allowing current to flow through this contact keeps the circuit closed thus the motor stays on. We than added another motor starter, now with two motor starters we added an additional relay in parallel with the first relay in each motor starter. These additional two relays will act as a H-bridge allowing us to turn set the motors in forward and reverse directions.
In this lab we used two different types of optocouplers, a component that transfers electrical signals between two isolated circuits by using light. Using LEDS within our circuit connecting to the internal IR LED and the phototransistor of the optocoupler, with proper circuit protection. We learned how in side of the Optocoupler it has two main components the Light source and a phototransistor when the light source is on it allows current to flow through the phototransistor. The two optocouplers we had test were one which has both components internally which has no physical way to block the light path, and one which had the two components separated which allowed us to physically block the path of light with an object such as a piece of paper. The purpose of an optocoupler is to be a opto-isolator which prevents one side of voltage from affecting the other usually a high voltage from affecting the system receiving a signal voltage.
In this lab we worked with 3 phase power we connected up two circuits a Wye and Delta circuit. Within each circuit we also had two versions a balanced and unbalanced condition. In the balanced all the line voltages are equal to each other, and all the currents are also equal to each other. In Unbalanced conditions usually due to the loads are not the being same. In the wye configuration we learned that the I-phase and the I-line are equal while the V-phase is less than the V-line. In Delta configuration V-phase equals V-line and I-phase is less than I-line.
In this lab we used a kill-a-watt meter to measure the volts, amps, watts, volt amps, frequency, and power factor of different loads. With just a resistor as a load we noticed how there is a watts being used but no apparent power. With just an inductor we have no real power but have an apparent power similarly as to just a capacitor as a load. With the combination of the two inductor and resistor or capacitor and resistor, we see we have real power and apparent power. However, when we use all three in a circuit we noticed that the resistor gives us real power, the inductor gives us an apparent power, and the capacitor gives an apparent power that counter acts the inductors apparent power thus giving us a lower apparent power overall.
In this lab while I was doing the lab made little sense to me. But now I understand what it was that I did. We had a DC motor attached to centrifugal load, the electro-dynamometer, that allow us to measure the torque from the motor. We connected the windings in series and pin parallel with the armature, or brushes, to see what the difference is. When the windings are connected in series with the armature we see that as torque goes up speed goes down as current goes up and voltage goes down respectively and vice versa. Whereas when we connect the windings in parallel with the armature we have a constant speed and the voltage remains the same.
In this lab we used a multi-winding transformer used on 110.120V systems, to learn about the different types of configurations of a transformer. The first was primary to secondary and we see our voltage go from 115V to 10V which is due to the turn ratio of the primary vs the secondary. Next we connected the primary to two secondaries’ in series which than gave us from 115V to 20V for each secondary gives us 10V and in series the voltages are added together. Next we connected two primaries in parallel to two secondaries’ in series which gives us 115V to 20V with a higher current rating. Next up was the two primaries interconnected in parallel with two secondaries’ also in parallel giving us 115V to 10V with a higher current rating. And finally we connected two primaries in series with two secondaries’ in parallel which gives us 230V to 10V which a hiver current however we were not able to reach 230V because the variac would not go that high.