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Engine control center
The MCC enclosure protects personnel from contact with live equipment and protects components from various environmental conditions. It is important that the enclosure is installed for accessibility so that qualified personnel (eg a trained thermography) can open the panel under load. There are different categories and types of My Customer Centers, but usually the My Customer Center file looks like a row of cabinets, where each cabinet represents a part of the My Customer Center service. File boxes represent accessories that contain electrical distribution and motor control components. Inside the MCC, the three-phase power is distributed by rails, large metal current-carrying bricks. The horizontal bus provides three-phase power distribution from the main power supply. The vertical bus of each section is connected to a different MCC. Support and insulation barriers protect against breakage. MCC plug-in modules have power connectors on the back so they can be connected to the vertical power line of the structure.
Let’s start the MCC infrared inspection
Before opening the engine control panel or door, check the enclosure to ensure safe opening conditions. If excessive heat is detected on the surface of the door, special care must be taken when opening it. A thermograph or transmitter may flag this condition as unacceptable and not use the option to open under load. After opening the unit, begin an infrared and visual inspection to ensure there are no hazardous conditions. Be regular when doing infrared inspections. Remember that the system must be under load to perform the check. Work from left to right or follow the circuit carefully and check all components. Look for unusual thermal patterns caused by high-impedance connections, overloads, or load imbalances. In a three-phase system, this can be done by comparing the phases. Adjust the IR level and range to optimize the image. Appropriate controls identify primary and secondary abnormalities. Bus spikes and network connections are important inspection points that are often overlooked or misdiagnosed. The future connection to the main horizontal rail is usually behind a cover or panel that is not hinged. These are usually bolted connections and can be parallel fed. It is more difficult to check the bus connections behind plug-in devices. The thermometer does not have a direct view of the connection, and the first sign of a fault is in the wires feeding the circuit breaker or when the fuse is removed. Remember that even a small increase in temperature observed at this stage can mean serious problems.
Motor starter and motor controller
The purpose of the motor starter is to protect the motor, personnel and related equipment. More than 90% of the motors in use are AC short circuit motors and a motor starter is used to start and stop them. A more general term refers to this device as a electrical distribution and motor control . The controller can have several functions such as start, stop, overload protection, and overload protection, reverse and braking. Adjust the motor starter to match the system voltage and horsepower. Other factors used in starter selection include: motor speed, torque, full load current (FLC), duty factor (SF) and time (10 or 20 seconds).
Understanding the thermal pattern of this device is critical to a successful inspection. Correct identification of the reason for the difference can also make recommendations more valuable.
Motors can be damaged or have a significantly shortened
lifespan if they are continuously operated at more than full load current. Motors are designed to withstand high speeds or locked rotor currents without significant temperature rise, provided that their duration and number of starts are limited. Overcurrents up to locked rotor current are usually caused by mechanical overloading of the motor. The National Electrical Code (NEC) describes overcurrent protection in this situation as “motorized overcurrent (overload) protection.” It can be reduced for overload protection.
Overcurrent’s caused by electrical equipment suppliers or ground faults are dramatically greater than overcurrent’s caused by mechanical overloads or excessive starts. The NEC describes this type of overcurrent protection as “motor branch circuit short circuit and ground fault protection”. It can be reduced to overcurrent protection. There are four common types of motor starters: cross starters, reversing starters, multi-speed starters, and low voltage starters. Motor starters are usually made of the same components. These include circuit breakers or fuses, contactors and overloads. There may be other parts, including control circuits and a transformer.
