Elevator Knowledge: Elevator Maintenance Personnel Must Master Some Common Sense.
With some basic knowledge, elevator engineers can bring a lot of convenience and ideas.
1. For those familiar with bridge rectifier, it is clear that the output voltage value of the filter capacitor is different from that of the unfiltered dc side. The dc side voltage of the filter capacitor is 1.2 to 1.4 times that of the ac input, while the output side voltage without the filter capacitor is 0.9 times that of the ac side. If you measure a rectifier circuit with a filter capacitor and find that the output side voltage is lower than the ac input side voltage, the filter capacitor is no longer working. Have a OTIS elevator inverter board testing 24 volts dc, once the monitoring found that 24 volts, or voltage is lower than the rating shall be reported to the PC board damage failure, if not carefully check would have thought that the computer fault can't timely troubleshooting. I happened to be hit by a malfunction like this, and I found that it was DC24 volts below 24 volts, which turned into 20 volts. Lower than the ac side voltage, the fault disappeared after the capacitor was changed, and the elevator was running normally.
2, half-wave rectifier in a transformation, the application of learning more than half wave rectification of all know, with a diode half-wave rectifier can be realized, after the half-wave rectifier dc output voltage is 0.45 times of the ac input. An early mitsubishi VVVVVVVVVVVVVVVVVV speed control elevator, the floor display of each floor is realized by lighting a light bulb to illuminate the plastic sheet with the floor number. Party a shall replace it with a digital tube display. According to the actual situation of the circuit, the electric light bulbs is AC100 v, I through a diode in the circuit, and then based on the digital tube circuit resistance of concatenated a matching resistance, successfully solve the problem. A diode string is equal to the half-wave rectifier, 100 v into 45 v, in combination of a resistance and with digital tube circuit of resistance partial pressure, so that from the control cabinet to the ac 100 v can for DC24 v dc digital tube display circuit power supply.
3. For example, if the frequency conversion speed regulating elevator stops down as soon as it slows down, what problem do you suspect in the first place? If you master the rule of elevator running, in what state is in a state of power generation, racing upward, loaded with downward, and slow runtime motor is in the power generation state, at this time of the brake unit if there is a fault can cause the elevator stopped ladder. This common sense applies to all types of variable frequency speed elevators manufactured by all manufacturers.
4. The ground system of the lightning rod of the primer should be separated from the ground system of the three-phase five-wire grounding alarm system, and a set of ground system should not be Shared. Harbin office elevator in a storm weather after a sound of thunder, the elevator stopped running, on-site inspection, found that the computer board is large current breakdown anxious burnt flavour permeates the whole room, through inspection building lightning rod guide LeiBian iron have a place to be welded to the building of reinforced concrete, concrete reinforcement is building grounding electrodes welded together.
5. Hidden secrets in ac/dc contactor
First of all, they all work on the same basis. The coil is electrified to generate magnetic field, which makes the moving armature attract and drive the switch to break.
The difference is one: an alternating current and a direct current. Second, the coil of dc contactor is larger than that of ac contactor. Third, the ac contactor has a short circuit ring in the core of the iron, but not in the dc contactor. This is explained in principle.
The key to understanding their differences is to understand the characteristics of ac and coil. China's electricity supply is 50hz, which means a change of 50 cycles in a second, with 100 instantaneous current zero.
Coil resistance is very small, winding in the dc power supply circuit performance for resistance characteristics, that is decided by the resistance of the coil voltage drop, has nothing to do with inductance, so the coil number of turns more make resistance, not burned power supply.
In ac power circuit, the coil with the characteristic impedance, the pressure drop through the impedance, the resistance value can be zero, so the number of turns can be unlike dc with so much, take some thick line also.
Ac contactor core has a short circuit ring, because ac contactor coil of alternating current (ac) is electric current pass by the zero moment, in the current zero moment there is no magnetic field in the coil, so moving iron core will release, and before it left, and the current in the coil, it was off, so suck, release, and repeat. 1 seconds have repeated one hundred times, it can form the noise, in order to eliminate the noise, engineers came up with a solution, embedded in the core, a is equal to the closing coil short circuit loop, when the contactor coil current through the zero short-circuit loop induced magnetic field, the induced magnetic field in the core magnetic field into a continuous magnetic field, thus to eliminate the noise. In use process, if the short circuit ring fracture, noise can appear, in an area where is sensitive to noise, replacing contactor is for this reason, sometimes not because contact broke.
According to the above reasons: the amount of copper used in dc contactor is large, the cost is high, the noise is low, and the cost of ac contactor is low.
6, electrolytic capacitor summary judgment: in the process of the elevator maintenance, often encounter some of the failure of computer board, sometimes through careful observation can avoid some big losses, computer fault on the surface, it is likely to be a capacitor failure, change the capacitance costs only a few yuan of money, and sent to repair board at hundreds of thousands of computer. Simply observe whether the end face of the electrolytic capacitor has been bulging, and if it has, in all likelihood, it will be replaced. Another way to do this is to set the digital multimeter to the buzzer file and use a red and black stylus to cross the positive and negative sides of the electrolytic capacitor.
7, the lightning rod and triggering lightning grounding three-phase five wire grounding is not mixed together, one day the weather after a thunder thunder and lightning Harbin office elevators shut, put people on the scene to check failure, found that the computer board area breakdown, carefully check the building lead LeiBian iron steel welded together with building main body, and the three-phase five wire grounding is welded together, with the cause of lightning electricity flows through the lightning flat iron flow backward into the elevator control system, led to the control system of north severely damaged.