Thirty-nine questions on professional terminology in the motor industry

 

1. What is alternating current?

The magnitude and direction of the current that changes with time is called alternating current. The electricity we use in our daily lives is alternating current.

Abbreviation: AC The following is the waveform of single-phase AC voltage

 

2. What is direct current?

The magnitude of DC current is generally stable, and there is no change in direction. DC power supply is generally a stable current. For example: battery power supply or AC power supply after rectification and filtering, etc.

Abbreviation: DC The following are the waveforms of several DC voltages

 

3. What is a DC speed regulator (DC brush motor speed regulator, DC motor speed regulator, DC motor speed regulator)

An electronic device that can drive and control the speed of a DC brush motor is called a DC speed regulator.

DC speed regulators are divided into: silicon controlled chopper type (SCR) and pulse width modulation type (PWM)

1. Thyristor type DC speed regulator

Advantages: low cost, easy to achieve high voltage, high power, good anti-interference performance, good impact resistance, low requirements on the use environment, etc.

Disadvantages: low speed regulation accuracy and high noise

Scope of application: Suitable for starting and running mechanical equipment with large operating torque and continuous operation, such as machine tools, drilling machines, grinders of machining equipment, continuously operating production equipment and equipment with low accuracy requirements.

2. What is pulse width modulation (PWM)?

Advantages: high speed regulation accuracy, low motor operation noise, high efficiency, wide speed regulation range, small motor operation sparks (can extend the service life of the motor), etc.

Disadvantages: poor impact resistance, large heat generation, large interference, large size, not suitable for high power, high requirements on the use environment, etc.

 

4. What is a servo controller (or servo control system) -------- Abbreviation: servo

"Servo" is defined as "servant". Usually refers to: being able to perform accurate positioning or speed operation according to the instructions received.

The servo controller has high speed control accuracy, powerful functions, and complete protection measures. The servo controller must have speed closed loop (tachometer generator or encoder feedback) and current closed loop control.

Servo controllers are divided into: DC brush servo, DC brushless servo and AC servo

DC brushed servo: refers to a system device that can drive and control the speed of a brushed motor (the rear shaft of the motor must have a tachometer generator or encoder). It is called: DC brushed servo.

Brushless DC servo: refers to a system device that can drive and control the speed of a brushless motor (the rear shaft of the motor must have an encoder). It is called: brushless DC servo.

Note: This system is generally sold together with a matching brushless motor, mainly to ensure control accuracy.

AC servo: The difference between AC servo and DC brushless servo is that the control method of the internal output waveform is different. The motor controlled is the same as the brushless DC motor. Currently, there are few domestically produced ones. Application occasions: Suitable for high control precision, Equipment with precise positioning and fast dynamic response, such as CNC machine tools, engraving machines, manipulators, etc.

 

5. What is an AC speed regulator?

AC speed regulator refers to an electronic device that can control the speed of an AC motor. AC speed regulators are divided into single-phase and three-phase speed regulators. Single-phase AC speed regulator: (referring to the power input of single-phase AC 220V), and simple Type and single-phase frequency converter speed regulation.

Three-phase AC speed regulator (referring to the power input as three-phase AC 380V). Currently, three-phase frequency converters are basically used for speed regulation.

 

6. What is a brushless DC motor controller?

Brushless DC motor speed regulator abbreviation: brushless controller,

A. The brushless DC motor is a dedicated and special three-phase AC motor, but its operation must be driven by a dedicated controller because the controller controls the motor through the DC pulse width modulation (PWM) principle. speed, so it is called a brushless DC motor speed regulator (brushless controller).

B. Brushless DC motor speed regulators are divided into two types: controllers with position feedback (Hall feedback) and controllers without position feedback (Hall feedback). The controller without position feedback is controlled by The motor requirements are not high, the control error is large, and the price of the whole set is low. It is currently mainly used in household appliances, such as household refrigerators, air conditioners, and electric bicycles.

 

7. What is an AC voltage regulating module?

AC voltage regulation - to put it simply: voltage regulation and control of AC power to achieve different output voltage requirements.​ 

Module - means small size.

 

8. What is the rated input voltage?

That is: the specified requirements for the voltage indicators at the input end of the product.

 

9. What is the rated output voltage?

That is: the regulation of the output voltage range of the product output end.

 

10. What is the rated output current?

That is: the current output by the product output terminal has a limited range.

 

11. What is the rated input voltage frequency?

That is: when the power input end of the product is AC power supply, the specified number of times the sine wave changes in unit time (unit time: times/second). The AC frequency used daily in our country is 50Hz/second. In some countries, the AC frequency is 60Hz/sec.

 

12. What is pulse width modulation (PWM)?

A circuit that fixes the pulse frequency and then adjusts the pulse width is called pulse width modulation (PWM)

 

13. What is thyristor chopper?

That is: through the one-way conduction characteristics of the thyristor, the AC sine wave is chopped to obtain the required output voltage.

Note: This method can only use thyristor chopper when the power supply adopts AC input.

 

14. What is short circuit protection?

Short circuit protection: Our product explanation means: the output current of the speed regulator does not flow through the normal load, but is connected through the abnormal load, resulting in the output current being much larger than the rated current of the driver. At this time, the internal current detection of the speed regulator The circuit is judged to be "over current" and protected, and the speed regulator stops output. This effectively protects the drive from damage.

 

15. What is overcurrent protection (can also be called: overcurrent protection, overload protection)

Over-current protection: The internal circuit of the speed regulator is equipped with an output current detection circuit. This circuit will detect changes in the output current in real time. When the circuit detects that the output current is greater than the set current value, it will be judged as an abnormal output current. At the same time, Block the output end of the speed regulator to stop the output or force the output current to be limited to the set value, thereby effectively protecting the speed regulator from damage caused by overcurrent, and also protecting the motor from overload or abnormal current of its own. of damage.

 

16. What is voltage feedback?

It means that in the loop of the speed control system, a certain proportion of the voltage value is collected at the output stage and introduced to the input stage in the form of negative feedback, and then the voltage of the output stage is monitored, compared and corrected in real time with the given value of the input stage, so as to This ensures that the voltage of the output stage follows and stabilizes within the range of the given value of the input stage. This method is called voltage negative feedback.

 

17. What is current feedback?

It means that in the loop of the speed control system, a current signal of a certain proportion is collected at the output stage and introduced to the input stage in the form of positive feedback, and then superimposed with the signal of the input stage to increase the voltage and current of the output stage. This method is called - current positive feedback

 

18. What is soft start?

It means that the motor speed reaches the set value through a slow acceleration process from the beginning. This process is called: soft start. The soft start process is measured in seconds.

 

19. What is soft stop?

It refers to the process in which the motor speed slowly decelerates from the set value to "0" speed. This process is called: soft stop. The soft stop process is measured in time "seconds".

 

20. What is torque compensation?

It means that when the motor is running (especially at low speed), the special circuit inside the speed regulator can detect the load torque of the motor in real time, and then automatically adjust the compensation value according to the setting value of the torque "compensation potentiometer".

 

21. What is open-loop control?

The so-called open loop means that the input and output do not form a closed loop. In theory, this control method has low control accuracy and poor stability. (Closed-loop control for our drives: generally refers to speed closed-loop)

Generally, open-loop speed regulators do not have high speed accuracy (up to 1% speed accuracy) and can only be used in situations with low requirements.

 

22. What is closed-loop control (also called "closed-loop feedback control") and speed feedback (speed feedback)

Closed loop: The output quantity is fed back (collected) and superimposed on the input quantity, compared with the given quantity, corrected, and then the output value is adjusted according to the error value to make the output value more stable within the given range.

Speed ​​feedback means that a tachometer generator or encoder is installed on the execution motor as a feedback element for closed-loop control. It can detect the error signal between the speed of the execution motor and a given expected value in real time, and then feed the error signal back to the system for dynamic correction processing. .

The advantages of this closed-loop method are: this control method has the advantages of high precision, stable control, fast dynamic response, good followability, and constant torque.

 

23. What is constant power speed regulation?

Constant power means that the power remains unchanged, and the speed and torque are inversely proportional; such as: stepper motor

 

24. What is constant torque speed regulation?

Constant torque means that the torque remains unchanged, and the speed and power are proportional.

 

25. What is a signal?

Signal - is to use weak instructions or commands to control powerful things. for example:

1. Traffic light signals on the road can control traffic order regularly.

2. The signals received by our controller can control the operation, start and stop of the motor, etc.

To put it simply: the information transmitted by various commands or instructions----------this is the "signal".

3. Switching signal (high/low level signal) - On/off signal refers to a "either on or off" signal, as shown in the figure:

 

 

Sometimes customers say: it is controlled by high and low levels (also switching signals), as shown in the picture above.

Note: The switching signal that needs to be connected to the power supply is called active switching quantity.

There is no need to connect the switching signal of the power supply (it can be solved directly by using an on/off switch) - it is called a passive switching signal.

 

26. What is standard signal input (analog signal)

Standard signals refer to signals that are jointly recognized, uniformly specified, and used in industry standards or international standards.

There are two types of standard signals: one is voltage type and the other is current type.

1. Voltage type: 0-5V 0-10V 0-- ±10V

(Some other countries also use 0-15V 0-24V)

2. Current type: 4-20mA 0-20mA

 

27. What is an analog signal (analog quantity)

Analog signal: It uses continuously changing numerical values ​​to represent various information to be explained.

For example: the above-mentioned (currently used) TV image signals use analog restoration technology to pass the image and sound signals through the transmission and reception circuits, and then restore the analog signals into images and sounds.

Furthermore, sketches and sketches are information observed through vision, which is restored into different scenery through the control of the body through brain memory ------- this is "simulation".

 

28. What is a digital signal (pulse amount)

Various information transmitted to each other in the form of pulses and digital codes are called digital signals.

The actual process is to embody and send various digital signals in the form of pulses, and finally decode and process this pulse signal through the transmission and reception circuit to restore it to the original information.

 

29. What is a signal isolator?

The signals used for transmission mean that they are separated from each other, independent, and do not affect each other.

 

30. What are stepless speed regulation and step speed regulation?

1. Stepless speed regulation means that the speed can be set or adjusted to any speed value within a certain range through adjustment.

2. What is step speed regulation? It refers to the speed regulation method within a certain range, in the form of steps. The speed can only change according to fixed gears and cannot be adjusted arbitrarily.

A simple example: when climbing to the same height, one is in the form of steps and the other is in the form of slow slopes. The steps represent stepped speed regulation, and the slow slope represents stepless speed regulation.

 

31. What is speed ratio?

The speed ratio refers to the ratio of the highest speed to the lowest speed when the torque is not lower than the rated value.

 

32. What is the speed range?

The speed range refers to the range from the lowest speed to the highest speed that can make the motor run.

 

33. What is four-quadrant operation?

The running speed direction of the motor is represented by a number axis X. The positive direction of the number axis represents the forward rotation speed, and the reverse direction represents the reverse rotation speed;

The direction of the electromagnetic torque of the motor is represented by a number axis Y. The positive direction of the number axis represents positive electromagnetic torque, and the reverse direction represents negative electromagnetic torque;

Constructing a plane coordinate system XOY, then the normal electric state of the motor is in the first quadrant (forward rotation, electric power), and the power generation (braking) regeneration operation is in the second quadrant (forward rotation, power generation).

The elevator traction motor continuously rotates forward and reverse due to its normal state. It may drive electricity or generate electricity in both upward and downward movements. It is in a four-quadrant operating state, and the energy conversion direction in each state is different.

Using the four quadrants to describe the operating status of the motor is the same as using the familiar forward, reverse, electric, and power generation descriptions.

 

34. The relationship between torque, power and speed of DC motor

T is torque (mN.m), P is power (W), N is rotation speed (r/min)

 

35. Performance comparison between brushless DC motor and brushed DC motor:

1. Brushless DC motor:

Advantages: Brushless motor has long service life, maintenance-free, small size, light weight, suitable for low power, etc.

Disadvantages: soft mechanical characteristics, poor overload capacity, small starting torque, etc.

2. Brushed DC motor

Disadvantages: Brushed DC motors have a short service life, require regular maintenance, and are large in size.

Advantages: Hard mechanical properties, strong overload capability, large starting torque, and can achieve high power, etc.

The current of the DC motor changes with the size of the load and is linear. This is why the speed regulation performance of the DC motor is very good.

 

36. Calculation method of DC motor current:

I = P / U / 0.8

I: Current A P: Power W U: Voltage V 0.8: Power factor of DC motor

 

37. Starting current of DC motor

The starting current of a DC motor when stationary is equal to the starting voltage ratio of the internal resistance (the internal resistance of a DC motor is particularly small, the greater the power, the smaller the internal resistance, and the power is inversely proportional to the internal resistance), but it is no longer the case after starting.

Therefore, the starting current of the DC motor is very large 

Generally, no-load startup is: 5-10 times

Start with load: 8-20 times (according to load conditions)

 

38. RS232 and RS485 instructions

The RS232 and RS485 interfaces are serial ports, which can communicate with the computer through dedicated data lines to modify the internal configuration parameters of the controller.

The intelligent DC motor speed regulators produced by Jinan Santang Electronics all come with RS232 RS485 CAN communication, etc. You can choose at will.

 

39. What is feedback method?

When the controller gives a command to the motor, the motor also sends a closed-loop feedback signal to the controller. This allows the controller to monitor the operating status of the motor in real time and improve the operating accuracy of the motor. Currently, the most commonly used ones are: Hall sensors, incremental encoders, speed measuring motors, etc.