AISIKAI

Jiangsu Aisikai Electric Co.,Ltd.(CE, CCC, ISO9001)

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Inverter common 10 faults and how to maintain

Inverter is power frequency by changing the motor work way to control the power of ac motor control device. Nowadays, with the constant improvement of the industrial automation level, frequency converter has been very widely used. Frequency converter has a lot of protection functions, such as over current, over voltage, overload protection, etc. Inverter, then, what are the common failures? Met inverter how common faults and maintenance process? The following introduction inverter how ten common faults and maintenance treatment.


A, overvoltage (OU)


Over-voltage alarm is generally appear in the downtime, the main reason is to slow down time is too short or braking resistor and brake unit has a problem.


For example:


When running a series of Ann N2 3.7 kW inverter in the downtime jump "OU".


Analysis and maintenance: before repairing the machine, the first thing to understand "OU" alarm why, this is because the frequency converter is slowing, motor rotor winding cutting speed rotating magnetic field, rotor electromotive force and the current increases, the motor is in a state power, the energy feedback through the inverter link with high power switch tube parallel diode to dc link, make dc bus voltage rise caused by, so we should focus on check brake circuit, measuring discharge resistance there is no problem, when measuring brake pipe (ET191) found a breakdown, running on electricity after replacement, and stop quickly.


Second, the over-current (OC)


The phenomenon of flow is the most frequent inverter alarm.


1. The phenomenon:


(1) restarts, a litre of tripping speed. This is very serious phenomenon over current. The main reasons are: the load short circuit, mechanical parts are stuck; Inverter module is damaged; The phenomenon such as the torque of the motor is too small.


(2) on the electric jump, this phenomenon is not reset, the main reasons are: bad, drive circuit, current detection circuit module. Reboot is not immediately trip but during acceleration, main reasons are: set acceleration time is too short, current limit set is too small, torque compensation (V/F) set is higher.


2. Example:


(1) a 3.7 kW inverter LG - IS3-4 start jump "OC"


Analysis and repair: open the machine cover didn't find any signs of burning, online measurement of IGBT basic judgment (7 mbr25nf - 120) there is no problem, in order to further determine problem, the IGBT removed after measuring seven units of high power transistor to open and close is very good. In the measurement at the half bridge driver circuit has the obvious difference with the other two way all the way, after careful examination revealed a light coupling A3120 output pin and anode short circuit, power supply to replace three after the road is essentially the same. All modules loaded up and electricity to run well.


(2) a BELTRO - VERT 2.2 kW frequency conversion power jump "OC" and cannot be reset.


Analysis and maintenance of: first check the inverter module found no problem. Second check drive circuit and no anomalies, estimation problem is not in this one, may be out of this area in the over current signal processing, the tear down later on electric circuit sensor, shows everything is normal, so think sensor has bad, looking for a new change after all normal load experiment.


Third, undervoltage (Uu)


Under-voltage and we often encounter problems in use. Mainly because of main loop is too low voltage (220 v series is lower than 200 v, 380 v series is lower than 400 v), the main reason: a rectifier bridge damage or silicon controlled all the way with work of three way in normal are likely to cause under-voltage fault, the second main circuit contactor is damaged, leading to loss of dc bus voltage on charge resistance may cause under-voltage. And the voltage detection circuit malfunction and undervoltage problems.


For example:


(1) a CT 18.5 kW inverter electric jump "Uu"


Analysis and maintenance: through inspection of the frequency converter rectifier bridge charge resistance are good, but didn't hear after electricity contactor action, because the charging circuit of frequency converter instead of using thyristor by contactor close to complete the process of absorption, so that failure may in the contactor or control circuit and the power part, disconnect the contactor with 24 v dc contactor work alone. Then check the 24 v dc power supply, carefully check the voltage is after LM7824 regulator tube voltage output, after measuring the voltage regulator tube has been damaged, after looking for a new product to replace the electrical work.


(2) a DANFOSS VLT5004 frequency converter, electric display is normal, but after add load jump "DCLINKUNDERVOLT" (low voltage dc circuit).


Analysis and maintenance: the frequency converter from phenomenon is special, but if you carefully look at the problem is not so complicated, the frequency converter is also through the charging circuit, contactor to complete the charging process, when the electricity didn't find any abnormal phenomenon, estimation is added when the load voltage drop caused by the dc circuit, the voltage of the dc circuit is through full-wave rectifier bridge rectifier, and then provided by capacitance after flat wave, so should check the rectifier bridge emphatically, has found that the measured open circuit, a bridge rectifier bridge arm after replacement of new problems to solve.


Four, overheating (OH) from overheating


Overheating overheating (OH) is a kind of common faults, main reason: ambient temperature is too high, fan is blocked, the temperature sensor performance is bad, motor overheating.


Example: an ABB ACS500 22 kw inverter customers reflected in running jump "OH" half an hour.


Analysis and repair: for it is defective only after running for a period of time, so the temperature sensors are unlikely to bad possibility that the temperature of the inverter is too high, after electrify found fan turn slowly, shield wall inside is full of a lot of cotton (because of the frequency converter is used in the textile industry), after cleaning the fan operation is good, the boot operation hours after didn't jump this failure.


Five, the unbalanced output


Unbalanced output performance for general motors jitter, speed instability, the main reason: module is bad, bad, drive circuit reactor is bad, etc.


For example:


A Fuji G9S 11 kw inverter output voltage is 100 v or so. Preliminary online analysis and maintenance: open the machine check inverter module (6 mbi50n - 120) didn't found the problem, measuring 6 road driving circuit also didn't find fault, the module will be removed measuring found along the way bridge power transistor conduction and close properly, the module has been damaged, after confirm the driver circuit trouble-free replacement product after everything is normal.


Six, damage of switch power supply


It is among the most common fault frequency converter, is usually caused by load short-circuit switch power supply, danfoss frequency converter USES a new type pulse width UC2844 integrated controller to adjust the output of the switch power supply, at the same time UC2844 with current, voltage feedback, and other functions, when no display and control terminal voltage, DC12V, 24 v fan is not running when the phenomenon such as the first thing we should consider whether the switch power supply damaged.


Seven, overload


Overload is one of the frequency converter to beat more frequent failure, usually see that overload phenomenon, we should first analyze the motor overload or overload, inverter itself in general motor due to overload ability is strong, as long as the motor parameter is set properly, the inverter parameter table generally appear unlikely to motor overload. The inverter itself is easy to be poor due to the overload capacity overload alarm. We can detect the inverter output voltage.


Eight, GF - ground fault


Ground fault is also will run into trouble at ordinary times, after controlling motor grounding the cause of the problem, is most likely to be part of the failure of hall sensors, hall sensor due to temperature, humidity and so on environment factor, the influence of working point slips occur easily, cause GF alarm.


Nine, current limiting operation


In normal times we may encounter in the operation of the inverter tip current limit. For general inverter in the current limit alarm appeared smooth work properly, voltage (frequency) must first down, until the scope of the current decline to allow once current is lower than the allowable values, voltage (frequency) will rise again, leading to the instability of the system. Danfoss frequency converter is controlled by internal slope, in the case of not exceed scheduled rhe looking for working point, and control the motor to run smoothly in the working point, warning signal feedback to customer and, according to the warning information to check whether the load and the motor is we have a problem.


Ten, SC failure


SC failure is sichuan inverter is one of the more common failure. Damage of IGBT module, which is one of the causes of SC fault alarm. Besides driving circuit damage is also easy to cause the SC fault alarm. On the design of drive circuit, yaskawa bridge using the drive coupling PC923 light, this is dedicated to driving IGBT module with a light coupling amplifying circuit, yaskawa bridge driving circuit is adopted under the light coupling PC929, it is an internal with amplifying circuit, optical coupling and detection circuit.


Jitter and motor, three phase current and voltage imbalance, frequency shows no voltage output, these phenomena could be damage of IGBT module. Damage of IGBT modules a variety of reasons, the first is external load malfunction and cause the damage of IGBT modules such as load short-circuit, locked-rotor, etc. Second drive circuit aging are also likely to lead to waveform distortion, or driving voltage fluctuation is too big and lead to damage of IGBT, resulting in SC fault alarm.


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    Update time:12/24/2015 10:18:16 AM  【Print this page】  【Close