Understanding this flow is a great aide in troubleshooting. Here's a simple example to analyze. In Fig. When either start pushbutton is depressed, the path is complete, and the coil of CR1 is energized. In following the path for the current, you can see the logic of the placement of the input devices. This logic determines the decision making process of the input devices and the path for current as it travels to energize the outputs. Logic statements. There are several logic statements that can be used in placing the input devices in the rungs. The end-to-end placement of the stop and start pushbuttons makes an AND logic statement.
In other words, both the stop AND the start buttons must be used to energize the coil. The parallel placements of the start buttons makes an OR logic statement. Either start pushbutton will complete the path and energize the coil.
Troubleshooting Industrial Electrical Equipment with a Multimeter and a Ladder Diagram - Kindle edition by L.W. Brittian. Download it once and read it on your. Troubleshooting Industrial Electrical Equipment with a Multimeter and a Ladder Diagram eBook: L.W. Brittian: usowujeq.gq: Kindle Store.
Placement of the output devices. As noted earlier, the output devices are placed on the right side of the ladder drawing. Unlike input devices, it's important that the output devices only be placed in parallel. If they are placed in series, electrical theory says that the voltage will drop across the resistance of each output. If this happens, they will not operate properly. Outputs include items such as lights, coils, solenoids, and heating elements.
In addition to the commonly accepted symbols shown in Fig. As noted by the numbers on the right rail, this circuit arrangement indicates there is a normally open contact in Rung 2 and a normally closed contact in Rung 3. Coils will typically have contacts associated with them. These contacts will change state when the coil is energized. The changing contacts will either complete or open the path for current.
As noted in Fig.
When the coil is energized, the contacts associated with the coil will change state. The red light will go on, and the green light will go off. Locating the contacts. In the ladder drawing, the contacts associated with the coil can be located using a cross-reference system. The rungs are usually numbered on the left side of the rail. A number on the right side of the rail references the contacts associated with the coil Fig. These numbers are the rungs in which the contacts can be found.
CircuitTesters A circuit tester is a device which is used to test a circuit to determine whether or not power is reaching the circuit. Circuit testers are very inexpensive tools which can be obtained at hardware and home suppliers, and they are critical tools for anyone who works with electricity to have. While they do not provide the detailed information available with a multimeter, they are useful for quick checking of electrical circuits, and they take no time at all to learn to use.
CircuitTesters Typically, a circuit tester has a light which illuminates when a circuit is getting power. Some may generate buzzing sounds, and the volume of the sound or the intensity of the light may increase with the amount of power available to the circuit. This can be useful for differentiating between circuits which are being supplied with different amounts of power, or for identifying circuits which are getting too much or too little power, which can be a sign of an electrical short or a similar problem.
Each time the waveform changes from zero to a peak value and back to zero is called an alternation.
Inductance in an AC Circuit Inductance is the characteristic of an AC electrical circuit that opposes the change of current flow. Capacitance The ability of an electrical component or circuit to store a charge in an AC circuit. No change in frequency — Must be used with a source voltage that varies in amplitude. Electric Motors Operation Electric motors function on the principle of magnetism; where like poles repel, and unlike poles attract.
DC Motors DC motors have been used in industry for many decades. When used with DC drives, they provide very precise control. DC MotorTerms Understanding the following terms will aid in identifying DC motor operation: Armature Current:The current required by a motor to produce torque and drive a load. Armature current is proportional to the amount of torque being produced. Base Speed:The motor shaft speed in revolutions per minute RPM that occurs when full armature voltage and full field current are supplied to a motor with a full load attached.
Commutation:The switching in polarity between the armature and the brushes in a DC motor that keeps current flowing in the same direction.
While ladder diagrams have their own unique elegance, it may be frustrating for some students to have to learn a new diagram convention. Since short circuits have such damaging impacts on electrical equipment, their impact on the components in the circuit must be understood. This is a common omission, done for the sake of simplicity. Electrical power systems deliver electricity to customers and to the plant. Discuss with your students the sources of electrical power for both circuits here: the relay control circuit and the motor itself. Time Delay Fuse These are generally dual element fuses with both thermal and instantaneous trip features that allow the motor starting current to flow for a short time without blowing the fuse.
Understanding the following terms will aid in identifying DC motor operation: Field Current:The current required to energize the field windings of a DC motor. The interaction between the armature current and field current produces flux in the motor Flux:The magnetic field created around an energized conductor or between opposite poles of a permanent magnet. Induction motors consist of a stator and a rotor enclosed within a frame, with no physical electrical connections between the stator and the rotor.
The stator consists of a core and windings, or coils, that convert electrical energy to the energy of a magnetic field. The stator magnetic field induces current in the rotor. The current creates a magnetic field and poles within the rotor. Motors:Wye Configuration Each phase coil A, B, and C is divided into two equal parts and the coils are connected in a standard wye connection.
Manufacturers of dual-voltage, 3- phase motors sometimes do not make the internal connections. The connections are made externally by the installer. Motors: Delta Configuration Each phase coil A, B, and C is divided into two equal parts and the coils are connected in a standard delta connection. A nameplate is a metal tag permanently attached to an electric motor frame that gives the required electrical ratings, operating ratings, and mechanical-design codes of the motor.
The voltage rating is the voltage level that a motor can use. All motors are designed for optimum performance at a specific voltage level. The current rating is the amount of current a motor draws when delivering full rated power output. The phase rating is the power phase 1f, 3f, or DC that a motor requires. Some electric motor drives allow the input power to the drive to be of a different type and at a different voltage level than the power required by the motor. The power rating is the amount of power a motor can deliver to a load.
Motors designed for the U. The service factor rating is a multiplier that represents the amount of extra load that can be placed on a motor without causing damage. Time Delay Fuse These are generally dual element fuses with both thermal and instantaneous trip features that allow the motor starting current to flow for a short time without blowing the fuse. Circuit Breakers Circuit Breakers are used instead of fuses due to the fact that fuses are a one time use only.
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Extra Content. Table of Contents Preface. Getting Started with Electrical Troubleshooting.