Some common problems in the field debugging of inverter

- Nov 01, 2019-

Inverter parameter setting

The parameter setting of inverter is very important in the process of debugging.Due to improper parameter setting, it can not meet the needs of production, resulting in the failure of starting and braking, or frequent tripping during work, which will burn down the power module IGBT or rectifier bridge and other devices.The variety of frequency converter is different, the number of parameters is also different. 

Generally, single-function inverter has about 50 ~ 60 parameter values, and multi-function inverter has more than 200 parameters.But no matter how many or few arguments you have, do you need to reset all of them during debugging?Not the, most can not change, as long as can be, according to the factory value when used as long as the original factory values are not suitable to reset can, such as external terminal operations, analog, basal frequency operation, the highest frequency, maximum frequency, lower frequency, start time, braking time (and), hot electron protection, over-current protection, carrier frequency, stalling protection and overvoltage protection must be reset.When the operation is not appropriate, then adjust other parameters.

400 Watt inverter

Field debugging common problems to deal with

The setting principle of starting time should be short but not long. See the specific value below.

The overcurrent setting OC is too small and appropriately increases to 150%.The experience value is 1.5 ~ 2s/kW, small power is larger;Larger than 30kW, >2s/kW.Press the start button *RUN, the motor is blocked.It indicates that the load torque is too large and the starting torque is too small (try to improve it).At this time to immediately press STOP parking, otherwise for a long time, the motor will burn. 

Since the motor does not rotate is in the state of blocked rotation, the anti-electrothermal E=0, at this time, the ac impedance value Z=0, only the dc resistance is very small, then, the current is very dangerous, so it is necessary to trip OC.Braking time set principle is appropriate long should not be short, easy to produce overpressure trip OE. 

It is advisable to apply free braking to the pump fan, and it is easy to produce serious "water hammer" effect when applying fast and strong braking.Starting frequency setting is favorable for accelerated starting, especially for light load. It is more applicable for heavy load starting frequency value, resulting in increased starting current. In low frequency band, it is easier to skip over current OC.Starting torque setting is favorable for accelerated starting, especially for light load. It is more applicable for heavy load with a large starting torque value, resulting in a higher starting current. In low frequency band, it is easier to skip the current OC. 

Base frequency the base frequency standard is set as 380V at 50Hz, that is, V/F=380/50=7.6.However, due to heavy load (such as extruder, washing machine, dryer, mixer, mixer, dehydrator, etc.) is often unable to start, and adjusting other parameters is often of no help, so adjusting the base frequency is an effective method.That is, the set value of 50Hz will decrease to 30Hz or below.At this time, V/F>7.6, namely, under the same frequency, especially in the low frequency band, the output voltage increases (i.e., torque protective U2).Therefore, the general heavy load can start well.Overvoltage during braking is caused by short braking time and too small braking resistance value, which can be avoided by increasing the resistance value through appropriate increasing time.

0.75kw Frequency Inverter

Selection of braking method

(1) energy consumption braking.With general braking, energy is expended on the resistance and dissipated in the form of heat.At a lower frequency, the braking torque is too small, to produce crawling phenomenon. 

(2) dc braking.Suitable for accurate parking or stop, no crawling phenomenon, can be combined with energy consumption braking, generally ≤20Hz dc braking, >20Hz energy consumption braking. 

(3) regenerative braking.Applicable to ≥100kW, speed regulation ratio D≥10, alternating between high and low speed or positive and negative rotation, cycle time is also short, in this case, applicable to regenerative braking, regenerative energy up to 20% of the motor power.More detailed analysis and parameter selection.No-load (or light load) jump OC arguably in no-load (or light load), the current is not large, should not jump OC, but actual happened phenomenon, the reason is often offset voltage is too high, large starting torque, the excitation saturation of serious, the exciting current distortion is serious, caused the peak current is too large and tripping OC, reduced or restore the factory values or placed in a 0 bit.

When starting, it jumps OC when the low frequency ≤20Hz, because of over-compensation, large starting torque, short starting time and small protection value (including overcurrent value and stall overcurrent value), it is ok to reduce the base frequency.It is difficult to start, unable to start the general equipment, the moment of inertia GD2 is too large, the resistance torque is too large, and heavy load starting, similar situations often occur in large fans, pumps, etc., solution:

  • reduce the base frequency; 

  • appropriately increase the initial frequency; 

  • appropriate to improve the starting torque; 

  • reduce the carrier frequency value 2.5 ~ 4kHz, increase the effective torque value; 

  • Reduce the starting time; 

  • Improve the protection value; 

  • make the load by carrying start into no load or light load, that is, the fan can be closed the inlet valve.The carrier frequency set by our company is 2.5kHz, lower than the usual. The purpose is to ensure the safety of use. However, it is generally reported that the above three problems exist.

After power transmission, press the start button to RUN and there is no response

(1) panel frequency is not set; 

(2) if the motor does not move, press "STOP" immediately and check the following items:

  • confirm the correctness of the line again; 

  • reconfirm the identified code (especially for the part related to starting); 

  • operation mode setting is right; 

  • measure the input voltage, R, S, T three-phase voltage; 

  • measuring dc PN voltage; 

  • measurement of switching power supply voltage; 

  • inspection of driver circuit plug-in contact; 

  • check the panel circuit plug-in contact situation; 

  • thoroughly check rear can again electrify.