Question

Why does the servo motor UVW power line have the wrong sequence connection, which causes the speed to suddenly increase?

Answer 1

In the past few days, I have seen some posts talking about the failure of the flying car caused by the wrong phase sequence connection of Fuji and Yaskawa Electric UVW power line, as for why the car is flying, I have thought in some posts that it is due to the wrong phase sequence, resulting in the reversal of the electrical angle and the positive feedback of the current loop, but did not give a specific phase sequence analysis. Today coincides with the work reason for this problem, so carefully consider the servo motor UVW power line sequence may lead to the electrical angle offset relationship, feel gained, first post the analysis results to share with you, if there is any objection, please do not hesitate to correct.

Consider that the electrical angle offset of the U-V-W normal access phase sequence is 0

The electrical angle offset of the U-W-V phase sequence is 180 degrees, exactly reversed, the Iq component is completely reversed, and the complete positive feedback, if the servo does not have a positive feedback detection mechanism, it will inevitably fly;

The electrical angle offset of the V-W-U phase sequence is 120 degrees, the phase offset exceeds 90 degrees, and the Iq component symbol is reversed to enter the positive feedback region;

The electrical angle offset of the V-U-W phase sequence is 300 degrees, that is, -60 degrees, the phase offset, the Iq component is halved, and the output force becomes significantly smaller, which can lead to a large actual current and serious heating of the motor;

The electrical angle offset of the W-U-V phase sequence is 240 degrees, that is, -120 degrees, the phase offset exceeds -90 degrees, and the Iq component sign is reversed and enters the positive feedback region;

The electrical angle offset of the W-V-U phase sequence is 60 degrees, the phase offset, the Iq component is halved, and the output force is significantly smaller, which can lead to a large actual current and serious heating of the motor.

The premise of this discussion is that assuming that the initial installation phase of the motor encoder is correct, the servo drive will completely "adopt" the electrical angle phase of the motor represented by the initial installation phase of the motor encoder, without the need for additional adjustment or identification of the electrical angle initial phase after the UVW power line wiring of the servo motor is connected, which is also the actual treatment of the vast majority of general-purpose servo systems currently supplied as complete sets.

There are six possible connections between the UVW three-phase power line of the motor and the UVW three-phase terminal of the driver, and the UVW sequence of the driver terminal is the correct access phase sequence, then the motor power line is connected to the driver terminal, including a one-to-one corresponding "normal access phase sequence" motor UVW to the driver UVW, according to the arrangement combination, there are a total of 6 possible access sequences, respectively, the UVW, UWV, VWU, VUW, WUV, WVU power line to the driver's UVW terminalTherefore, the U, V, and W terminals of the drive may be connected to the U or V or W phase power lines of the motor, respectively. Since the back EMF phase on the power line of the motor represents the actual electric angle of the motor, and the phase between the output voltage and current waveforms of the UVW terminal of the drive depends on the electric angle of determining the phase sequence represented by the motor encoder phase, therefore, when the correspondence between the UVW phase of the motor power line and the UVW terminal of the drive is different, the deviation between the phase of the drive voltage and current waveform and the motor back EMF phase will occur, and the relevant deviations are as follows:
 
Taking the phase sequence of the motor power line UVW to the driver UVW terminal one-to-one corresponding to the phase sequence of "normal access" as the reference phase sequence, according to the general phase relationship of three-phase alternating current, U leads V120 degrees, V leads W120 degrees, that is, U leads W240 degrees, then there are:

U-V-W accesses the phase sequence normally.

The electrical angle offset is 0, the electrical angle increment is +Δθ, and the subsequent electric angle can be expressed as: +Δθ.

The angle of the starting current vector increases from 270 degrees in the α-β coordinate and the current vector angle in the D-Q coordinate system always points to the 270 direction to achieve quadrature decoupling.

At this point, the servo control is always in an optimal state of complete quadrature decoupling.

Both the current loop and the speed loop operate normally.
U-W-V phase sequence, U is correct, W and V are reversed.

The electrical angle offset is 180 degrees, the electrical angle increment is -Δθ, and the subsequent electric angle can be expressed as: 180 - Δθ.

In the α-β coordinates, the starting current vector angle decreases from 90 degrees in reverse, the current vector angle in the D-Q coordinate system decreases by 2 times from the 90 direction, the starting direction deviates from the original orthogonal direction (270 degrees) 180 degrees orthogonally to the D axis, and gradually the deviation from the orthogonal direction tends to the D axis direction (0 degrees).
Since the motor electrical angle increment direction and the drive vector direction reversed, the Iq component is a function of cos(180-2Δθ), the starting phase of the 90 direction is exactly reversed, the Iq component is reversed by 180 degrees, under the current loop, the motor instantly reverses, with the rotation of the motor, the Iq component quickly appears zero value, and finally locks to die at this point. In the speed ring operation mode, it will also lock up after instantaneous.
V-W-U phase sequence, the order of each phase of the motor and the drive is misaligned.

The electrical angle offset is +120 degrees, the electrical angle increment is +Δθ, and the subsequent electrical angle can be expressed as: 120 + Δθ.

In the α-β coordinates, the starting current vector angle increases from 30 degrees, and in the D-Q coordinate system, the current vector angle always points in the 30 direction, deviating from the original orthogonal direction (270 degrees direction) + 120 degrees.

Since the motor electrical angle increment direction is consistent with the drive, the Iq component is cos(120)=-0.5, the sign is reversed, and under the current loop, the motor is reversed and the torque is reduced. In the speed ring operation mode, the speed is fed back to the speeder.

Answer 2

If it is 300 degrees and 60 degrees, can the drive detect it?

Answer 3

To add: In the above analysis, the phase relationship between the so-called "normal access phase sequence" U-V-W is that V is ahead of U120 degrees, W is ahead of V120 degrees, that is, W is ahead of U240 degrees. [Need to be corrected] "V lag U120 degrees, W lag V120 degrees, that is, W lag U240 degrees", or "U ahead of V120 degrees, V ahead of W120 degrees, that is, U ahead of W240 degrees".

To add another point: in the above discussion, assuming that the initial installation phase of the motor encoder is correct, the servo drive "adopts" the initial installation phase of the motor encoder, and "does not pass again" [restricts] "no longer passes" the initial phase of the electrical angle to detect or adjust the electrical angle initial phase through the UVW power line of the servo motor, and the actual processing methods of most general-purpose servos at present are in line with this assumption.

Answer 4

If U/V/W is connected, but the zero angle setting angle in the servo system is deviated from the actual angle, it should also be applied according to the above results.

Answer 5

Today I encountered the X axis and the Y axis with Panasonic servo, but the Y-axis PE and W are reversed, there is no alarm and trip after power-on, it is normal, but after giving the same instruction, the Y-axis speed is slower than the X-axis, and the Y axis fluctuates relatively large, when running the X-axis alone, after a few seconds, the Y axis drives the overvoltage alarm, and the Y axis is no problem running the Y axis alone, but the speed is a little slow. 

I remember that when I used to use Mitsubishi, when I connected the wrong phase sequence, I would call the police, and if I connected it wrong with PE, it would trip directly. I don't know how to explain this problem, please enlighten Bonn. I was confused.

Answer 6

Connect the wrong U with a Panasonic servo. V。 W does not affect and the motor does not reverse.

Answer 7

In principle, the servo system should have output phase loss protection and positive feedback protection!

With positive feedback protection, even if the phase order is wrong, there will be no flying car, after all, flying car is a very dangerous thing, according to several people upstairs, Panasonic connected the wrong car, it means that Panasonic has protection, this point is in place;

With the output phase loss protection, it will not be in the case of output disconnection, still working too abnormally, the problem described in the "7th floor" is very dangerous, W and PE are connected to each other, the motor casing will be electrified, there will be a personal accident! At this time, W is connected to PE, and there is no electrical relationship relative to UV, which is equivalent to W phase loss, so Panasonic's protection mechanism is not in place at this point! 

As for the reason why the motor will still rotate at this time, I haven't thought it out for a while, and the PE end does not do leakage protection, it is estimated that it is a problem of electrical wiring, not necessarily in the servo.

Answer 8

"The electrical angle offset of the U-W-V phase sequence is 180 degrees, exactly reversed, the Iq component is completely reversed, completely positive feedback, if the servo does not have a positive feedback detection mechanism, it will inevitably fly;"

According to past experience, when wiring in this way, the motor seems to lock up after turning to a certain position, and the driver outputs ~~ at maximum current

Have time to verify again

Answer 9

"The electrical angular offset of the U-W-V phase sequence is 180 degrees"

The U-W-V phase sequence here means that the U phase of the drive is connected to the U phase of the motor, the V phase of the drive is connected to the W phase of the motor, and the W phase of the drive is connected to the V phase of the motor?

Also: How to understand the electrical angle offset?

Answer 10

The motor UVW phase sequence is reversed, and if the initial phase judgment is not made, an overcurrent alarm will occur at power-on. Because the phase angle of vector control is wrong, not for the reason of positive feedback, refer to the vector control principle and the modulation principle such as SVPWM.

The correct process is as follows:

After the phase sequence is wrong, it is best to perform the initial phase search when powering on, and general drivers, such as Yaskawa, have this function. 

After finding the initial phase, if the motor is flying, you need to modify a reference direction setting in the drive, which is to modify the positive feedback to negative feedback, the specific reason is that the speed given value is opposite to the actual speed value calculated by the encoder.

In general, if the phase sequence is connected incorrectly without looking for the initial phase, the power-on driver must overcurrent alarm.

Answer 11

"Under normal circumstances, if the phase sequence is connected incorrectly without looking for the initial phase, the power-on driver must overcurrent alarm."

Sometimes there will be an overload alarm ~~ This is generally caused by positive feedback of current.

In fact, the positive feedback of the current is caused by the wrong phase angle. The Bonn brothers also said so~~ The views are not much different. ~~

"The correct process is as follows: After the phase sequence is connected incorrectly, it is best to perform the initial phase search when powering on, and general drivers, such as Yaskawa, have this function. After finding the initial phase, if the motor speed suddenly increases, you need to modify a reference direction setting in the drive, which is to modify the positive feedback to negative feedback, because the speed given value and the actual speed value calculated by the encoder sign are opposite. ”

The solution you are talking about is for sudden increases in rotational speed caused by positive velocity feedback, which is discussed here. When the phase angle is wrong, it will also cause a sudden increase in servo motor speed.