The torque limit is set, whether it is also the limit of the current Please explain in detail

My opinion: In vector control, the total current sqrt (excitation current.

square + torque current squared), when the torque is limited, it has nothing to do with the excitation current, and the relationship between the torque current and the torque is what the friend on the 3rd floor said, so when the torque is limited, the torque current is also limited. I've used one called Inovance.

The torque limit function of the MD320 device, when limiting the torque percentage, by observing the total current, is in line with the above rules, and, under certain speed change conditions, stalled rotor can occur, this function is a more interesting thing, there is a use in special cases, MM4 speed mode limits torque, I think the principle is similar, but there is no special test for the wrong, please correct.

The upstairs is good, but the language is too concise. Let me be more explicit. For Siemens devices, whether AC or DC controllers.

The torque limiting is not the fundamental limit, the fundamental limit, is the current multiple of the rectifier inverter device, in the case of MM440, that is, the parameter P0640, his size, determines the total current limit of the device and the motor.

You can test it, it is a DC motor, and it can be roughly considered that the torque limit and the armature current limit correspond to the weak magnetic point, and the weak magnetic point is inconsistent. If it is an AC motor, there is no direct relationship between the current limiting and the torque limiting.

It can't be too general, when the torque limit is 100%, it depends on the current limit.

Dear friends, after setting the torque limit, when the motor stalls, will the inverter report an overcurrent fault?

"Torque limiting control, the method adopted is the saturation of the speed regulator; Torque is given and the speed regulator bypass is used. "Well said, top it! Torque limiting control, when the speed ring has a large speed deviation input signal, the speed ring's PI regulator output"Saturation"。

Then, the output of the velocity regulator in the saturated state is limited, which is the torque limiting. We're always there"Soft connections", torque limiting control is used. In strip production lines, paper machine production lines, acrylic production lines, etc., load distribution between transmission rollers can be considered"Torque limiting control"。

The speed of the driven roller is given the same value as that of the driving roller, and the speed of the driven roller is given by about 2% 5%, and the speed ring of the driven roller will be saturated. The torque of the driving roller is used to control the torque limiting of the driven roller to ensure that the output of the driven roller is not greater than that of the driving roller at any time. View the original post

These two are actually the same, but the requirements of the process are different. A torque is often reached to the rated value, and the speed is not yet there. The other torque is less than the limit and the speed is up to the rated value.

However, there is one that is understood. That is, the torque priority level is high, that is, the torque reaches a limit value, regardless of the given value of speed. The torque limit is not reached, and the speed is subject to the speed given.

Why is it that when the difference between the given speed and the actual speed is too large under the torque limiting, the encoder feedback malfunction alarm will easily occur? That is to say, if the torque limiting is not carried out, the motor will definitely exert its strength to run the actual speed to the given position of the speed; However, after adding the torque limit, the torque is limited, and the speed will definitely not be reached, so the result of my test is that the encoder is often out of order alarm; And when the torque is controlled, there is no such phenomenon, how is this explained View the original post

The effect of current feedback is to limit the maximum value of the current, which is effective at all times. However, it does not work, but depends on the rise time of the current. For example, when the motor leads are short-circuited, although the control system has a current limit, the current will be exceeded before the current limit can be effective.

Hold fast melting or frying device. In other words, the current limiting is the first line of defense for system overcurrent protection. If the speed of the overcurrent is too fast, it will rush through the first line of defense of the current limit, and "advance" to the second line of defense of the system.

The function of positive current feedback is to speed up the rise of current. It is equivalent to a short circuit of the motor load. Therefore, the current limiting does not work.

It will pass through quickly and make a quick melt or short circuit protection action.

When the diode is forward conducted, when the current is greater than 1mA, the voltage at both ends is about , which is a fixed value; For example, when there is a current flowing through the two ends of the wire, we think that the resistance of the wire is zero, and the voltage is 0 V. When the diode is forward-conducted, you can think of it as the equivalent of having a voltage source, adding the voltage source of uref=, what is the voltage at both ends? I don't need to talk about it, just think about the experiment of stringing several batteries together to light up a small light bulb when you think about it.

Diode limiting circuit: The conduction and cut-off of the diode are used to achieve the limiting effect.

Transistor limiting circuit: The transistor limiting circuit uses the output of the triode to enter the cut-off zone or saturation zone to achieve the limiting effect.

A circuit that can flatten the amplitude of the signal voltage wave within a limited range, also known as a limiter or clipper. Limiting circuits are commonly used for: shaping, such as cutting out interference at the top or bottom of the output waveform; Waveform transformation, such as cutting out the positive pulses in the output signal, leaving only the negative pulses in it; Overvoltage protection, such as when a strong output signal or interference has the potential to damage a component, can be connected to the limiting circuit in front of the component.

Let's put it this way, when the ui is greater than uref, the diode is turned on, the current flows through the diode back to the negative pole of ui, and the power supply e is considered a short circuit state at this time. All the current flows through the diode, and the multi-external UO can only get a voltage of 3V.

In the ideal model, the tube pressure drop is equal to 0When it is greater than 3V, it will be turned on, so it will become flat; In the constant voltage drop model, the voltage at both ends of the voltage is constant when it is on, that is, the on-voltage, becauseThe constant pressure drop model is not an ideal model, so add a pressure drop.

The UI voltage will always be higher than U0 to play a limiting role.

Suppose the Ui voltage rises and the U0(UREF+ voltage remains constant, then the voltage rise of the resistor R increases.

If the UI voltage decreases and the U0(uref+ voltage is constant), then the voltage on R will also decrease as the UI decreases.

That is to say, UI-U0=VR (voltage on the resistor), and all voltages above U0 on the UI are added to the resistor R.

Another point resistor, R, can also act as a current limiting (to prevent a short circuit at U0).

uo=ud when ui-uref>=ud; UI-UREF analysis, 1. UI plays a separate role: the current of the circuit i=(ui-ud) r, so the resistor plays the role of limiting the current and protecting the 2 transistors. On the other hand, the 2-diode has a certain capacitance, and it can also cancel the high frequency in series with R.

2. ULEF Sole function: because the 2 diodes are reversed in the circuit, no current is generated. Unless it is broken through.

1, and 2 add up to the beginning of the equation. (UD is the on-voltage of a 2-transistor).

I would venture to ask, are you a student? Still ask this?

If there is no resistor R, aren't the UI and UO at the same potential?

R acts as a voltage divider, distributing the voltage that exceeds the limit to R.

That's not what it means! Tension speed control is widely used in strip handling and rolling, and the usual strategy is "speed saturation, torque limiting", and the speed is set to prevent speeding. In fact, speed control is still used, because Siemens' inverter does not support ping-pong control, that is, direct torque control (ABB can).

In general processing, I give a speed and limit the torque at the same time, for example, the speed given is 50, but in fact the motor does not run to 50, because the motor does not work at the rated torque, it has been limited.

My rewinding and unwinding rolls and main rolls are driven by mm440+ asynchronous motors, for example, the speed of my reference roll is given to 300m min, and the tension is given to 100N, should the given speed of the unwinding motor be 300m min-fixed value, and the given speed of the winding motor is greater than 300m min+fixed value? And how much should this fixed value be taken?

I do two-stage tension control, I want to take the speed given plus torque limiting method to control the winding and unwinding tension, I will calculate the given torque of the winding and unwinding motor, but I just don't know what this given speed should be? How to give it, can you combine it?

Then you should first introduce the structure of this rewinding and unwinding system. See what the demands of his workflow are? Then we will discuss the specific control plan. What are the requirements on site?

This first needs to understand the speed current double closed-loop system, the output of the speed loop is used as the input of the current loop, and the control tension is to control the tension torque converted into the tension moment, and how to accurately control the tension moment, for example, my tension moment is 20% of the reference torque, at this time I have to add a torque limit in front of the current ring, this torque limit is the required 20%, how to ensure that what is my limit value, how much torque my current loop gets, This is to ensure that the output of my front speed loop is maximum, that is, 100% of the maximum torque, and then what is my limiting value, the current loop is how much, and in order to ensure that the output ring is maximum, this requires my speed loop to be saturated, that is, to add an additional speed to the main given or feedback value, to give this additional speed when building static tension, and at the same time convert the tension you need into a torque limiting value to the inverter, you can get all the tension.

Sort of"Halo"In fact, I am very grateful for the impatient guidance of the teachers, and I also feel very guilty, sometimes I don't understand and ask, in fact, looking for books, I can also know, become very lazy, waste other people's precious time, and lose the opportunity to learn and understand systematically. --I feel that there is little control of variable inertia, so I ask about it.

I like Xia Li's question very much, and I say it very simply and naively. In fact, if you want to understand these problems, you must understand the principle of AC and DC drive control. Relying only on others to say that we can only know what it is, and only by mastering the principle can we know why it is true.

The principle of transmission, in fact, take the textbook and the function diagram of Siemens' use of the encyclopedia, try to deduce his working process, and then you will understand why the limiting adjustment, why the speed regulator will be saturated, and so on. The saturation of the speed regulator is the condition for the torque limiting to work, and the torque limiting is the result of achieving tension control. These things are linked one after the other.

There is both a distinction and an intrinsic necessity. A bit of a philosophical flavor. If you look at the transmission control, you can't understand the typical control structure of double closed loop.

Therefore, it is enough to specialize in a book "AC and DC Closed-loop Transmission Control System". It would be nice if there was another teacher to guide me.

The 250a part should have a time limit, and it can only be allowed to last as long as it can last. Like overtaking while driving.

This means that this motor is allowed to be overloaded almost 3 times.

Isn't the general motor 2 times?