Frequency Converter Common sense

What is a frequency converter.

The frequency converter is the power control device which transforms the power frequency supply into another frequency by using the switching function of the electric semiconductor device. The frequency converter is the power control device which transforms the power frequency supply into another frequency by using the switching function of the electric semiconductor device. Can be divided into AC-ac frequency converter, ac-Straight-AC frequency converter.

AC-Frequency converter can directly convert alternating current into alternating current with variable frequency and voltage;

Cross-direct-to-AC inverter is the first to convert the alternating current through the rectifier to DC, and then through the inverter to the DC to the frequency and voltage are variable alternating current

what are the different points of PWM and Pam.

PWM is the English pulse width modulation (pulse wide modulation) abbreviation, according to a certain law change pulse width, in order to adjust the output and waveform of a nice value way. Pam is the English pulse amplitude modulation (impulse amplitude modulation) abbreviation, is to change the pulse amplitude according to certain law, in order to adjust the output value and waveform of a modulation mode.

the voltage type is different from the current type.

The main circuit of the inverter can be broadly divided into two types: the voltage is the DC conversion of the voltage source to AC inverter, the DC circuit filter is the capacitance, the current type is the DC conversion of the current source to AC converter, its DC circuit filter stone inductor.

why the voltage and current of the inverter are proportional to the change.

Induction motor torque is the motor's magnetic flux and the rotor flow through the interaction between the current, at the rated frequency, if the voltage must only reduce the frequency, then the magnetic flux is too large, the magnetic circuit saturation, serious will burn down the motor. Therefore, the frequency and voltage to be proportional to change, that is, change the frequency of the inverter output voltage control, so that the motor flux to maintain a certain, to avoid weak magnetic and magnetic saturation phenomenon. This kind of control method is used in fan, pump energy-saving frequency converter.

when the motor drives the frequency power supply, the voltage decreases and the current increases, and if the frequency decreases, the current increases if the voltage decreases.

When the frequency drops (low speed), if the output of the same power, then the current increases, but under the condition of the torque, the current is almost unchanged.

when the frequency converter is used, the starting current and starting torque of the motor.

With the use of frequency converter operation, with the acceleration of the motor to increase the frequency and voltage, the starting current is limited to 150% rated current below (according to the type of machine, for 125%~200%). When the frequency power supply is started directly, the starting current is 6~7 times, so the impact on mechanical and electrical will be generated. The drive with frequency converter can be started smoothly (starting time becomes longer). Starting current is the rated current of 1.2~1.5 times, the starting torque is 70%~120% rated torque, for the inverter with automatic torque enhancement, starting torque of 100% or more, you can take full load start.

what does the V/F mode mean.

When the frequency drops, the voltage V also decreases proportionally, and this question has been answered in 4 instructions. The ratio of V to f is predetermined by considering the characteristics of the motor, usually having several characteristics in the controller's storage device (ROM), which can be selected with a switch or dial.

the torque of the motor varies proportionally to V and F.

When the frequency drops completely proportionally reduces the voltage, then due to the AC impedance is smaller and the DC resistance is not changed, will cause the torque at low speed to reduce the tendency. Therefore, at low frequencies given V/F, to increase the output voltage, in order to obtain a certain starting torque, this compensation is called enhanced starting. Can be implemented in a variety of ways, there are automatic methods, choose V/F mode or adjust the potentiometer and so on.

in the manual is written on the variable speed range 60~6hz, that is, 10:1, then there is no output power below 6Hz.

Under 6Hz can still output power, but according to the motor temperature rise and starting torque size and other conditions, the lowest frequency of use around 6Hz, at this time the motor can output rated torque without causing serious heat problems. The actual output frequency (starting frequency) of the frequency converter is 0.5~3hz according to the machine type.

for the general motor combination is above 60Hz also requires torque must be, whether it is possible.

Normally, it is not possible. Above 60Hz (also has more than 50Hz mode) voltage constant, the general is the constant power characteristic, at the high speed requires the same torque, must pay attention to the motor and the frequency converter capacity choice.

what does the so-called open loop mean.

For the motor device used to set the speed detector (PG), the actual speed feedback to the control device for control, called "Closed loop", without the operation of PG called "open-loop". Universal Frequency Converter is open-loop mode, but also some of the machine to use the option can be PG feedback.

how the actual speed is biased for a given speed.

When opening the loop, the motor speed is changed within the rated slip range (1%~5%), even when the motor is running with load at a given frequency. For the requirements of high precision speed, even if the load changes are required at near a given speed of the operation of the occasion, can be used with PG feedback function of the inverter (optional pieces).

if using a motor with PG, the speed accuracy can be improved after feedback.

The frequency converter with PG feedback function can improve the accuracy. But the speed accuracy of the plant depends on the accuracy of the PG itself and the resolution of the frequency converter output.
You master, there are c51 single-machine to step into the electronic method can discuss it? Both the editor and the C language are available. My current method org000bhjnbp0.0,go//p0.0 AJMPplusgo:AJMPposhSETBEASETBEX0plus:MOVTH0, #0FEHMOVTL0, #0CHDJNZ6BH, return2// Measured pulse volume mov6bh,60hclrp0.0ajmpreturn2posh:movth0, #0FEHMOVTL0, #0CHDJNZ6BH, return2mov6bh,60hsetbp0.0inc60h// The high inc70h//has been developed and low

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