Analysis and solution of the brake failure of the

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The analysis and solution of crane brake failure

this paper mainly introduces the failure of ydwz-490/100ja brake in the main lifting mechanism of a 15/3t L-type gantry crane. When the power is turned on, the push rod of my1-l00ja hydraulic electromagnet (hereinafter referred to as electromagnet) only moves upward by about 10mm, which is 15mm different from the working stroke. Therefore, the brake shoe cannot be released, and the lifting system cannot work normally

1. Fault analysis:

the common reasons for the small stroke of the electromagnet push rod are:

a. there is air or insufficient oil in the electromagnet cavity

b. the compensation stroke exceeds the specified value of the model

c. coil open circuit or low voltage at both ends

d. electromagnet damage, etc

at the fault site, we analyzed the common causes listed from simple to complex one by one. First, fill the electromagnet with oil and exhaust the air. The fault still exists. Check the compensation stroke. The distance between the upper end of the push rod and the upper cover is only 15m. The combination of production, learning, research and enterprise is m. reason 2 can also be denied. After power on, use a multimeter to measure the two voltages of the silicon rectifier. The input voltage is 380V and the output voltage is 340v, which is completely normal. A new electromagnet is connected to the output end of the silicon rectifier, and the same fault phenomenon occurs, indicating that the electromagnet itself is not damaged. What is the reason for the failure? Figure 1 is the electrical schematic diagram of silicon rectifier, an electromagnet power supply device, which can save a lot of oil resources. We analyzed its working principle. When the AC 380V voltage is added to the input end, the KM action normally open contact closes to connect the circuit, and the Ka normally closed contact shortens the economic resistance R. at the output end, a DC voltage of approximately 340v is obtained as the suction voltage of the electromagnet. When an electromagnet is connected to the output end, current flows through the electromagnet coil. Because the coil is a large inductive load, the DC current needs a transition process before UL F1 shows that the material can also be used outdoors to reach a steady-state value. When the current rises to the electromagnet closing current IM, the electromagnet closes and the push rod rises to complete the brake release process of the brake frame. When the current continues to rise to the action of current relay KA and the setting current is, the relay acts, and its normally closed contact connects the economic resistance R to the circuit, and the output voltage drops to the holding voltage of the electromagnet

Figure 1 electrical schematic diagram of silicon rectifier

repeatedly turn on and off the power supply, observe the action time of the current relay and the action time of the push rod on the silicon rectifier, and find that when the push rod rises about 10mm, the electromagnet has not been closed, but the current relay acts, and the economic resistance R is connected to the circuit too early. This indicates that the setting current ij of the current relay is less than the electromagnet pickup current im. Therefore, the normally closed contact of the current relay acts before the electromagnet is attracted, so that the push rod cannot rise to the normal position, and the brake cannot be released

2. Solutions

adjust the action time of the current relay on the silicon rectifier so that the action time of its normally closed contact lags about 0.5s behind the electromagnet pull-in time, and then connect the economic resistance R. the first stage includes injecting 8 LSR materials with different colors. Through the analysis and treatment of the cause of the fault and repeated operation on site, the ydwz-400/100ja brake was released and the brake was normal, and the fault was eliminated. It is proved that the fault treatment effect is good

for crane brakes with similar faults, do not replace the hydraulic electromagnet at will to avoid waste

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