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A common failure of the converter

The inverter has been widely used in industrial and agricultural production.I do a summary for some common faults of frequency converter, hope in the future inverter maintenance work can provide some help to you.Common failure are as follows.

1 overcurrent trip

The phenomenon of over current is the most frequent inverter alarm.Is often electricity jump, generally can't reset the phenomenon, the main reasons are: module damage, damage of drive circuit, current detection circuit damage.

Restarts, a litre of tripping speed.The main reasons are load or short-circuit;Mechanical stuck, inverter tube damage, small motor starting torque, drag system turns up.

Reboot not tripping immediately, but in the running process (including up and slow down operation) in the trip, the possible reasons: set up time is too short;Slow down the time set too short;Torque compensation (U/F ratio) set is bigger, cause low frequency load current is too large of time and space;Improper electronic thermal relay setting, action current setting is too small, cause misoperation.Like a 3.7 kW inverter LG - IS3-4 one start jump \"OC\".Open the machine cover didn't find any signs of burning, online measurement of IGBT basic no problem (7 mbr25nf - 120), 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 road is essentially the same, after all good modules installed on the power.Again, like a single BELTRO - VERT 2.2 kW inverter power jump \"OC\", and cannot be reset.First check the inverter module, found no problem, then check the drive circuit and no abnormal phenomenon, estimates that the problem in the current signal processing parts, the sensor circuit disconnect the electricity, after shows everything is normal, so think sensor has bad, looking for a new product after the change, on load.

2 the overvoltage trip

The main cause of overvoltage trip: power supply voltage is too high;Slow down the time set too short;Slow down the process of regenerative braking discharge unit of work is not ideal, doesn't include discharge (should increase external braking resistor and brake unit) and discharge branch fails, the practice is not discharge.Like a 7-day N2 3.7 kW series inverter in the downtime to jump \"OU\".Before repairing the machine, should first clear \"OU\" alarm why, this is because the inverter in the deceleration, motor rotor winding cutting speed rotating magnetic field, rotor electromotive force and the current increases, the motor is in power position, feedback of energy flow through the diode in the links of inverter dc link, make dc bus voltage rise caused by, so you should inspect the brake circuit, measuring discharge resistance found no problem, then measure the brake pipe (ET191) found a breakdown, change after the power, and stop quickly.

3 under voltage trip

The cause of under voltage trip: power supply voltage is too low;Link up the phase indicator;Rectifier bridge failures.As a CT jump \"Uu\" 18.5 kW inverter power.Examined the frequency converter rectifier bridge charge resistance are good, but didn't hear contactor action after the electricity, because the charging circuit does not use the thyristor inverter, but by the contactor and to complete the charging process, so that failure may in the contactor or control circuit and power supply section.Disconnect the contactor alone with 24 V direct current, contactor work normally.Then check the 24 V dc power supply, after careful examination, the voltage is after LM7824 regulator tube voltage output, after measuring the voltage regulator tube has been damaged, looking for a new replacement after electrify work normally.As sets of DANFOSS VLT5004 frequency converter, electric display is normal, but after loading the \"DC LINK UNDERVOLT\" (low voltage DC circuit).The frequency converter is also done through the charging circuit contactor in the process of charging, did not find any abnormal phenomenon, when electricity is add 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 change the new problem is resolved.

4 overheating

Overheating is also a kind of common failures, the main reasons are the ambient temperature is too high, fan locked-rotor, temperature sensor performance is bad, motor overheating, etc.If the inverter control center in the summer of refrigeration, ventilated effect is poor, the environment temperature, are often jump stop overheating protection.Then should check the fan frequency converter internal damage, operation room temperature is high, forced cooling measures should be taken to ensure the safety of the inverter of the summer.

5 unbalanced output

Unbalanced output jitter, average performance for motor speed instability, the main reason for the module is damaged, drive circuit damage, damage to the reactor, etc.As Taiwan Fuji G9S 11 kW inverter, output voltage is 100 V or so.Open the machine initial online examination, found no inverter module (6 mbi50n - 120) has a problem, measuring the six-way drive circuit also didn't find fault, the module will be removed measurement, high power transistor is found to be unable the normal conduction and closed, the module has been damaged.

6 overload

Overload is one of the frequency converter to beat more frequent failure, usually see overload phenomenon, maintenance personnel shall, first of all, analysis of motor overload or overload, inverter itself in general motor due to overload ability is strong, as long as the inverter parameter table motor parameter is set properly, general won't appear the motor overload.The inverter itself is easy to be poor due to the overload capacity overload alarm, can detect the inverter output voltage.

7 damage of switch power supply

This is 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, the phenomenon such as DC12V / 24 v fan is not operating, maintenance personnel should first consider whether the switch power supply damaged.

8 SC failure

SC failure is sichuan inverter is one of the more common failure.Damage of IGBT modules, is one of the causes of SC fault alarm, and drive circuit damage is easy to cause the SC fault alarm.Jitter in addition, motor, three phase current, 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.

9 current-limiting run

In normal times 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.Frequency converter is controlled by internal slope, in the case of not exceed scheduled rhe looking for working point, control the motor to run smoothly in the working point, and will feedback the alarm signal to the customer, on the basis of the alarm information maintenance personnel to check the load and the motor if there's any problem.