Test method for Delta Circuit breakers AC contactors and frequency converters

1. Circuit breaker

The circuit breaker is a device that can be operated manually or automatically. It is used to control the on-off of the system power supply in the circuit system of the device. When a fault is suspected in the circuit system of the equipment, the primary functional components of the power supply should be checked.

In normal cases, when the input and output terminals are in on state, they are also on (that is, powered on). When it is in the off state, the input and output terminals are also in the off state.

When the circuit breaker is repaired in the circuit, its on-off condition characteristics in the case of power failure are used. The resistance value between the input end and the output end of the circuit breaker can be measured by a multimeter.

Normally, when the Drisy circuit breaker is off, the resistance between the input and output terminals should be infinite; When the circuit breaker is on, the resistance between the input and output terminals should be zero; If this rule is not met, the circuit breaker is damaged and should be replaced with the same standard circuit breaker.

2. Ac contactor

Ac contactor is an important component in the circuit system. It mainly uses its internal main contact to control the on-off condition of equipment load, and uses auxiliary contact to execute control instructions.

The primary device of AC contactor is in the control distribution cabinet of the circuit system, which is used to receive the signal from the control terminal, and then the electrical contact action of the coil (normally open contact closed, normally closed contact disconnected), and the load starts to power on. When the coil power and release, all contacts reset, load power and stop.

If the AC contactor is damaged, the equipment cannot start or operate normally. The first way to judge its function is to use a multimeter to judge whether the resistance between the coil and the corresponding pin is normal in the case of AC contactor power off.

When the internal coil of AC contactor is energized, the internal contact will have the opposite action to the initial condition, that is, normally open contact closed, normally closed contact disconnected; When the internal coil power, its internal contact reset, recovery of the initial condition.

Thus, when testing contactors, it is necessary to test, in turn, the resistance of the internal coil and the resistance of its internal contacts in the open and closed condition. Because the contactor power test, normally open contact resistance value is infinite. When the switch button at the top of the communication contactor is pressed, the normally open contact closes and its resistance value is usually zero ohm.

3. Frequency Converter

In the equipment circuit system, the circuit system device controlled by the frequency converter is in the control box. As a central control component, the frequency converter is mainly used to control the running condition of various motors and compressors in the system.

Therefore, when the frequency converter is abnormal, the whole frequency conversion control system will also be abnormal. The function of the inverter is normal, the first can be determined by detecting the power supply voltage and output control signal of the inverter.

If the input voltage is normal and there is no frequency conversion drive signal output, the frequency converter itself is abnormal.

Because the inverter is a delicate electronic device that includes a variety of circuits, it is possible to troubleshoot the fault code displayed on the display in addition to the input and output when it is tested, such as the Mitsubishi FR-A700 inverter. If the display displays "ELF", it indicates that there is a problem with the output phase of the converter. The output terminal should be connected normally, and check whether the selected value of output phase break protection is normal.

The service life of frequency converter is also affected by the external environment, such as temperature and humidity. Therefore, the location of the device frequency converter should be under the conditions of its surrounding environment. In addition, the device should be careful when connecting the cable. If the connection is wrong, the frequency converter will be damaged. In order to prevent electric shock, it is also necessary to ground the ground terminal of the inverter.