The Motor Control Center
The MCC enclosure protects people against contact with electrical devices, and protects the components from different environments. It 'important that the body is connected, to ensure accessibility, so that qualified personnel (for example, trained a thermal imaging) can open the panel under load. There are different classes and types of MCC, but is generally seen as a series of MCC cabinets, each cabinet with an equalMCC section. The drawers of the archives are plug-in units for controlling the engine components. Three-phase power distribution within the MCC with the bus bars, large metal objects, power bars for transportation. The bus provides horizontal three-phase distribution from the mains. Vertical bus in each section of it is connected to each MCC. Reinforcement and insulation barriers are designed to protect against failures. The plug-in units have a power rises to MCChis back, which are connected the electrical power of the vertical power structure.
Jump Starter
MCC starting your infrared image
Before opening a door panel or a controller engine, the opening slot to ensure a safe pre-scan state. If there is excessive heat on the surface of the door should be especially careful when it will open. The thermographers or guardian may decide to observe the unacceptable condition and not a chance in the opening under load. Once you open the device,beginning in order to avoid either an infrared and a visual inspection of potential hazardous conditions. Be systematic in carrying out the inspection of infrared light. Remember, the system must be under load, to perform the inspection. Working from left to right or follow the trail carefully inspect all components. Looking through the high resistance connections, overloaded or load imbalances caused by abnormal thermal patterns. In three-phase systems, this can be done by comparing the phases. Togetherthe level and scope of the infrared system to optimize the image. The right attitude is identified primary and secondary abnormalities. Stabs the bus and the link to the main checkpoints are important, often overlooked or misdiagnosed. The inbound connection to the horizontal main bus is usually behind a cover or disguise, are not removed fold. These are typically bolted connections in parallel and may have investors. The connectors on the back of the bus bars plug-in units aremore difficult to control. Thermography has no direct view of the connection, and the first signs of a problem, refer to the return wire feed the fused disconnect switch or to be seen. He could remember, even small increases in temperature at this point means serious problems identified.
Motor and regulator
The purpose of the starter, is to protect the engine, personnel and related equipment. About 90% of the engines used are induction motors,and motor starters are used to start and stop. A generic term that identifies this device as a motor controller. A controller can have multiple functions such as start, stop, over-current protection, surge protection, reverse and brake. The engine is selected to match the power and performance of the system. Other factors for the choice of starters: motor speed, torque, full load current (FLC), the service factor (SF), and evaluation of the time (10 or 20Seconds).
The understanding of the thermal model of these systems is crucial for a successful test. In addition to correctly identify the source of the anomaly can provide valuable recommendations.
Motor can be damaged or the quality of life are significantly reduced when operating continuously with a current above full load current. The motors are designed for in-rush current or locked rotor without increasing much in temperature control, provided that there is a limited duration and a limited number ofbegins. About to start-up current flows are usually caused by mechanical overload of the motor. The National Electric Code NEC () describes the over-current protection for this situation as a "motor running overcurrent (overload) protection." This can be reduced to overload. Currents caused by short circuits or earth faults were caused, are significantly greater than that caused by mechanical overload or excessive begins. The NEC describes this type of surge protection as an "engine.. Branch-circuit short circuit and ground fault protection: "This can be reduced to over-current protection The four common varieties are the starter motor. Across the line, reverse, multi-speed starter, starters, and the reduction Engine start-up voltage is generally the same types of components. This includes a circuit breaker or fused disconnect, contactor and overload. It may also include additional components, including control electronics and a transformer. Understandingthe thermal model of these systems is crucial for a successful test. Even properly identify the source of the anomaly can give valuable suggestions.
Surge protector
NEC sets the overcurrent protection and a means to separate the motor and controller from the network. Fused disconnects or circuit breakers are generally used for overcurrent protection and disconnect one of the circuit are. A switch is defined in NEMAStandards as a device for opening and closing of a circuit made of non-automatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within their ratings. If we look at a section of a switch, we can connect with potential problems. The line side and load side studs are the most common cause of abnormal heating, but many of the switches have a second set of screws on the back of the hammer. Heat from this contextcan be interpreted as a main lug. There are also internal contacts where the current flow is interrupted by the exercise component. These contacts arches experience every time you open the switch. An arc is a derivative of jumps of electrical current through an air gap between two contacts. Arches are formed when the contacts of a switch to open under load. Arches under normal load is very small compared to a sheet formed by a short circuit interruption. Arcs generated additionalHeat and can damage the contact surfaces. Damaged terminals can cause heat resistance. Thermal model of these connections are bad heat spread over the surface of the hammer. They are also used different types of mills, the inner coil for short circuit protection. These coils heat associated with them and they can obviously be a problem of internal heating, when in fact it is a normal state.
Fuse Disconnects
Drop zone are used to provideOvercurrent protection for the engine in the same way as a mill. Instead of opening the contacts, fuses to fail open circuit. If over-current protection is provided by fuse, a switch for manual opening of the circuit is required. The disconnectors and fuse block are typically an assembly. The hinge connectors and the switch blade is a typical source of overheating. High resistance due to overuse or underuse is usually the cause. Fuse clips are also a weak point of connectionseparated for some drawings. Different types or manufacturers of the same amperage fuse may lead to different thermal signatures. While other size or amperage fuses also have a different thermal models can fuse body to appear warmer than the rest of the circuit depending on the size of the conductor.
Sagittarius
Appetizers consist of two components, contactors and overload protection. Sagittarius control the flow of electric current to the motor. Their function is alwaysestablish and interrupt an electrical circuit. A contactor can stand alone as a control unit of power, or as part of an appetizer. Electromechanical contactors operate with a small control current to open and close the circuit. The electromechanical components to do the job, not the human hand, as is the case with a knife or a manual control switch. The sequence of operation of a contactor as follows: First, a control current flow is applied to the coil, the current in the nextThe coil generates a magnetic field that is magnetized so that the e-frame, and finally an electromagnet pulls the armature solenoid her, closing the contacts. A contactor has a life expectancy. When the relay contacts are opened and closed frequently, is the life of the device. Since the contacts are applied, an electric arc between the contacts was created. Arcs produce heat that can damage the contacts. The contacts are oxidized at last with a black deposit. Thisblack deposit can actually improve the electrical connection between the contacts through the improvement of the seat, but burn marks, show pitting and corrosion, it is time to replace the contacts. The following thermal patterns associated with Sagittarius. The coil of the contactor is usually the hottest part of the device. High temperatures can reduce a coil. The line side and load side connections flap may indicate excessive heating of the bad links. Heater burnt andpitted contacts may thermally "visible" on the body of the contactor.
Overload protection
The ideal protection against motor overload is a unit of measurement of current with similar functionality to the heating curve of the engine. It would be the circuit of the motor full load current is exceeded. Allow the operation of this unit with motor overloads harmless temporary operation, but open when an overload is too long.
Typical thermal overload problems found inLinks to the contactor, overload relay, or motor.
This protection can be provided through the use of a thermal relay. The relay restricts the amount of current is designed to protect the engine from overheating. It consists of a unit to monitor the flow and a mechanism to open the circuit. A relay is renewable and can travel again and restore cycles. Traffic congestion, but do not provide protection against short circuits. The cast alloy (or eutectic) consists of a thermal relayHeating coil, a eutectic alloy, and a mechanism to activate a mechanical release mechanism, when congestion occurs. The relay measures the temperature of the engine by monitoring the amount of power consumption. This is indirectly through a heating element that melts when overloaded, a special alloy allows one wheel to rotate freely Ratchet and did open the contact. A bimetallic thermal overload is a U-shaped bimetal. Leads to an overload of heat used to direct the bimetaland opens a contact. The solid state relay does not heat up because of a trip. Instead, the existing arrangements or a change in resistance. The advantage of this method is that the overload relay does not generate heat energy and cooling requirements to complete the panel. Heating normal thermal overload can be tried as an anomaly. Heat in the bimetal coil or can be created to look like a connection problem. Typical thermal overload problems found inLinks to the contactor, overload relay, or motor.
Appetizers
Appetizers are the combination of a controller, typically a contactor and relay. The above descriptions of the individual components apply to the starter. Starters are used in applications that require high power motors are involved. They are used to lower the inrush current and torque, and therefore the mechanical stress load. The components of this type of starter issubsidiaries, as the steps in the cycle of the engine. A separate low voltage circuit is used to start the engine up to date. Once the speed of operation, these components are de-stress.
Inspection complete
Remember that the primary abnormalities of the problems that stand out slightly, while secondary abnormalities may require that the main anomalies are adapted to saturation to allow for the identification of a secondary fault. For example, the size of backup and lead to various differentthermal signatures are the relays that are different in size within the same circuit. Anomalies such as these should be identified and reported. Also note that in assessing the gravity of the problem, the temperature is only one variable. All parameters with the severity of the anomaly are involved, must be considered. To improve temperature measurements in order to avoid low-emission surfaces. Search cavity radiators or isolation that emits a highly conductive. Load measurement, the componentImbalances sizing, overload or load are observed. Caution to the winds and convection influences of the components. Note temperatures, large temperature gradients, and the heating source. Security should be considered the tip.
Completion
Knowledge of the equipment under control is the correct identification of problems that may be misinterpreted or overlooked. Analyze the unknown samples to a thermal component design is easier when the device has occurred. AccurateRecommendations for repair can be made. Identifying differences in temperature are qualitatively and quantitatively the main advantage of infrared thermography. Knowing where to come looking for these differences in temperature from the knowledge of the equipment and knowledge of equipment to make a better thermography.
Guidelines for performing infrared inspections of Motor Control Center
No comments:
Post a Comment