Rockwell AB inverter maintenance case
Come across a case equipment can not run, according to the manual check the fan and the temperature of the converter, the current is normal, normal fault was found, then we rockwell AB high voltage inverter maintenance engineer examination revealed is located in the inverter) (modules above a three wire inside lines of (with) the fan is broken, sometimes the dust fan can run but also can make the inverter show this failure!Because the fan of inverter radiator is normal, general person does not know inverter to still have this fan inside again!This caused a lot of confusion.
Encounter a lot of customers in the calculation of inverter (energy saving with) investment payback period, the inverter life cost and maintenance cost is not very good to calculate up!In fact, these will lead to a great difference in the service life of the equipment, some use 5-6 years before ** times of maintenance, some just after the warranty period began to frequent maintenance!Some of the poor performance of the inverter a damage almost no maintenance value!Inverter fault is generally the module burned out, and this module price is usually not low!The maintenance bill will blow your mind!So in the purchase of inverter maintenance cost life cost is also to focus on the problem.
About rockwell AB high voltage inverter maintenance a few additional notes: the equipment will only buck, not boost.Device itself is not the economizer, the energy cannot be speed regulation is built on the original waste, on the basis of energy device is an electromagnetic interference, equipment cost difference is very big, the service life of the difference is very big, charging SCR is broken is sometimes difficult to find, or its/AB inverter control circuit does not work and repair bad, then can use a relay to replace the SCR (current) appropriately, relay control voltage can be directly to the switch power supply 24 v or 12 v (cooling fan power supply), relay price is low, so also can save the maintenance cost.If the relay cannot be installed in the inverter, the lead can be installed next to the inverter.The life of the equipment is not infinite, the fan and electrolytic capacitor * first aging, equipment is a combination of strong and weak electricity, motherboard circuit precision, poor working environment and maintenance is high failure rate.
Rockwell AB during maintenance of high voltage inverter debugging tips: sometimes use multiple period of speed (also called pace), such as industrial washing machines, multiple period of speed is composed of several period of speed function of terminals to control the different actions of relations, this relationship is different, different equipment so that if use, no experience is difficult to set the period of speed according to the requirements of the original.We operate like this: connect the control line first, do not connect the motor, speed up the parameters of the newly installed equipment -- frequency 1, frequency 2, frequency 3, frequency 4.......Set as 1Hz, 2Hz, 3Hz, 4Hz......, that is, set all the speed of the section as its number, and then start the converter.If you command the device to run at a high speed of 160 Hz, then if the display is 4Hz, you can set the segment speed parameter "frequency 4" to "160 Hz", and the same is true for other segments
The basic principle of American AB inverter
American AB inverter is an electric power control device that transforms the power frequency power supply to another frequency by using the on-off action of power semiconductor devices. It can realize the functions of soft starting of ac asynchronous motor, variable frequency speed regulation, improving operation accuracy, changing power factor, over current/over voltage/overload protection, etc.
The main circuit of American AB inverter can be roughly divided into two types: the voltage type is the converter that transforms the dc of the voltage source into the ac, and the filter of the dc circuit is the capacitor.Current type is the converter that converts the dc of current source into ac, and the dc circuit filter is the inductance.
Why is the voltage proportional to the frequency of the American AB inverter changed?
The electromagnetic torque of any motor is the result of the interaction between the current and the flux.Therefore, if the magnetic flux decreases, the electromagnetic torque must also decrease, resulting in a reduction in the carrying capacity.
According to formula E = 4.44 * K * F * N *, it can be seen that the magnetic circuit of the motor varies in a considerable range with the running frequency fX when the frequency conversion is adjusted. It is very easy to make the magnetic circuit of the motor seriously saturated, resulting in serious waveform distortion of the excitation current, resulting in a high peak current.
Therefore, the frequency and voltage should be changed proportionally, that is, the output voltage of the inverter is controlled while the frequency is changed, so that the magnetic flux of the motor is kept constant and the occurrence of weak magnetism and magnetic saturation phenomenon is avoided.This control method is mainly used for fan, pump energy - saving inverter.
5. When the motor drives the manual frequency power supply, the current increases when the voltage drops;For a inverter drive, if the voltage decreases as the frequency decreases, does the current increase?When the frequency decreases (at low speed), the current increases if the output power is the same, but the current is almost unchanged under certain torque conditions.
6. What is the starting current and starting torque of the motor when the frequency converter is used?
The starting current is limited to 150% of rated current (125%~200% according to the type of machine).When the power supply is started directly, the starting current is 6~7 times of the rated current, so the mechanical and electrical shock will be generated.The use of inverter drive can be started smoothly (starting time is longer).The starting current is 1.2~1.5 times of the rated current, and the starting torque is 70%~120% of the rated torque.For the frequency converter with automatic torque enhancement function, the starting torque is more than 100% and can be started with full load.
7. What is the meaning of V/f mode?
When the frequency drops, the voltage V also decreases proportionately.The ratio of V to f is predetermined taking into account the characteristics of the motor. There are usually several characteristics in the storage device (ROM) of the controller, which can be selected by a switch or a dial.
8. How does the torque of the motor change when V and f are changed proportionally?
When the frequency drops, the voltage is reduced in full proportion, so the ground torque will tend to decrease at low speed because the ac impedance becomes smaller and the dc resistance remains unchanged.Therefore, given V/f at low frequencies, the output voltage should be increased to obtain a certain starting torque. This compensation is called enhanced starting.It can be realized by various methods, such as automatic method, V/f mode selection or potentiometer adjustment.