16 basic knowledge of Elevator Inverter

Lift Heroes

1, what is the frequency converter?

Frequency converter is a power control device which uses the power of the power semiconductor device to change the power frequency to another frequency.

2, PWM and PAM the difference is what?

PWM is English Pulse Width Modulation (pulse width modulation), according to the law must change the pulse of the pulse width in a tone adjustment output and waveform. PAM is the English Amplitude Modulation Pulse (pulse amplitude modulation) abbreviation, is according to a certain law to change the pulse of the pulse amplitude, in order to adjust the output value and waveform of a modulation.

3. What is the difference between voltage and current?

The main circuit of the inverter can be divided into two categories: voltage is DC voltage source converter for AC inverter, the DC circuit is the filter capacitor current is DC converter; current source for AC inverter, the DC circuit filter inductance stone.

4, why the inverter voltage and current proportional change?

Asynchronous motor is the torque between the current flowing through the motor flux and rotor as a result of the interaction, at rated frequency, but only if the voltage will reduce the frequency, then the magnetic flux on a large magnetic circuit saturation, the motor will be seriously burned. Therefore, frequency and voltage to be proportional to change, that is to change the frequency of the frequency control inverter output voltage, so that the flux of the motor to maintain a certain, to avoid the phenomenon of weak magnetic and magnetic saturation. This means more control for fan and pump energy saving converter.

5, the use of power frequency motor driver, the voltage drop is the current increase; for the inverter driver, if the frequency decreases when the voltage is also decreased, then the current is increased?

When the output is at low speed, if the output is the same power, the current is increased, but the current is almost constant under the condition of a certain torque.

6, the use of inverter operation, the motor starting current, starting torque, how?

A transducer operation, with the acceleration of motor voltage and higher frequency, the starting current is limited to 150% below the rated current (according to the different types of aircraft, 125%~200%). Starting with power frequency power supply, the starting current is 6~7 times, therefore, the impact on the mechanical and electrical. The inverter drive can be smoothly start (start time longer). The starting current is 1.2~1.5 times of the rated current, the starting torque is 70%~120% rated torque, the starting torque is more than 100%, and the starting torque is more than, which can be started with full load.

7, what is the meaning of the V/f model?

The frequency drop when the voltage V is also proportional to the drop, this problem has been answered in the 4 note. The proportional relationship between V and F is considered in the pre decision of motor characteristics, and there are several characteristics in the controller's storage device (ROM).

8, according to the ratio of V and F to change, how to change the torque motor?

When the frequency is down, the voltage is reduced completely, and the DC resistance is changed due to the AC impedance, and the torque at low speed is reduced. Therefore, when a low frequency is given V/f, the output voltage can be increased to obtain a certain starting torque, which is called enhanced starting. Can use a variety of methods to achieve, there is an automatic method, select the V/f mode or adjust the potentiometer and other methods.

9, in the description of the transmission range 60~6Hz, that is, 10:1, then there is no power in the following 6Hz?

Below 6Hz can still be output power, but according to the motor temperature rise and the starting torque of the size and other conditions, the minimum frequency of use of 6Hz or so, at this time the motor can be output rated torque without causing serious problems. The actual output frequency converter (frequency) based on 0.5~3Hz model.

10, for the general motor combination is above 60Hz also requires a certain torque, can you?

Usually when it is not possible. In the 60Hz above (also has 50Hz above the mode) voltage is constant, generally for the constant power characteristics, at high speed under the same torque requirements, must pay attention to the motor and the inverter capacity choice.

11, the so-called open ring is what mean?

To the use of the motor device set speed detection device (PG), the actual speed feedback to the control device to control, known as the "closed loop", do not have to run the PG is called "open loop"". Central to the more generic transducer, and some types of aircraft can use the pieces for PG feedback.

12, the actual speed for a given speed when there is a deviation of how to do?

Open loop, inverter output even given frequency motor operation in a load range, the motor speed in the rated slip ratio (1%~5%) changes. For the requirements of relatively high precision, even if the load changes are also required at a given speed in the operation of the occasion, can be used with the PG feedback function of the inverter (optional).

13, if the motor with PG, feedback speed accuracy can be improved?

Inverter with PG feedback function, the accuracy is improved. But the speed precision of the plant depends on the accuracy of the PG itself and the frequency of the frequency converter output resolution.

14, what is the meaning of the stall to prevent the function?

If the given acceleration time is too short, the frequency of the inverter output is far more than the speed change (Electrical angular frequency) of the change, the inverter will be due to flow over the current trip, the operation stopped, which is called stall. In order to prevent the motor from running, the current should be checked for frequency control. When the current is too large to slow down the speed of the appropriate to slow down. So is the deceleration. The combination of the two is the function of stall.

15, the aircraft acceleration time and deceleration time were given, and the deceleration time common given aircraft, what is the significance of this?

Slowdown were to be added to the aircraft for a short time to accelerate and slow speed is suitable for occasions, or small machine tools needed to set strict production time of the occasion, but for the fan drive, the slowdown has had a longer time, the acceleration time and deceleration time can be common.

16, what is the regenerative braking?

If the motor is running, if the frequency is reduced, the motor is changed to an asynchronous generator, which is used as a brake.

Back：Empty! Next：How to make the size of the elevator steel structure well Return