For electrical and other professional friends, motor is a common equipment. In the previous article, we have introduced servo motor and torque motor. In order to enhance our understanding of the motor, this paper will introduce the variable frequency motor, mainly to elaborate the principle and wiring of the variable frequency motor. If you are interested in motor related knowledge, you may as well continue to read on.
1、 Principle of variable frequency motor
Variable frequency motor is a kind of motor that runs continuously in the range of 10% ~ 100% rated speed with 100% rated load under standard environmental conditions, and the temperature rise will not exceed the allowable value of the motor.
With the rapid development of power electronic technology and new semiconductor devices, the AC speed control technology has been constantly improved. The gradually improved inverter is widely used in AC motor with its good output waveform and excellent performance price ratio. For example, large and medium-sized roller table motors, traction motors for railway and urban rail transit, elevator motors, lifting motors for container lifting equipment, motors for water pump and fan, compressors, and household appliances used in steel rolling have successively used AC variable frequency speed regulating motors, and achieved good results. Compared with DC motor, AC motor has obvious advantages
(1) It’s easy to adjust speed and energy-saving.
(2) AC motor has the advantages of simple structure, small volume, small inertia, low cost, easy maintenance and durability.
(3) It can expand capacity and realize high speed and high voltage operation.
(4) It can realize soft start and fast braking.
(5) No spark, explosion-proof, strong environmental adaptability.
2、 Characteristics of variable frequency motor
The special motor for frequency conversion has the following characteristics:
Class B temperature rise design, class F insulation manufacturing. The use of polymer insulation materials and vacuum pressure impregnation manufacturing process, as well as the use of special insulation structure, greatly improves the insulation withstand voltage and mechanical strength of the electrical winding, which is competent for the high-speed operation of the motor and resistance to the high-frequency current impact of the inverter and the damage of voltage to the insulation.
The balance quality is high, the vibration level is R (vibration reduction level), the machining accuracy of mechanical parts is high, and the special high-precision bearing is used, which can run at high speed.
Forced ventilation cooling system, all imported axial fan, super quiet, high life, strong wind. Ensure that the motor at any speed, get effective heat dissipation, can achieve high-speed or low-speed long-term operation.
Compared with the traditional variable frequency motor, the YP series motor designed by amcad software has a wider speed range and higher design quality. Through the special magnetic field design, it further suppresses the high harmonic magnetic field to meet the design index of broadband, energy saving and low noise. It has the characteristics of wide range constant torque and power speed regulation, stable speed regulation and no torque ripple.
It has good parameter matching with all kinds of frequency converters. With vector control, it can realize zero speed full torque, low frequency large torque and high precision speed control, position control and fast dynamic response control. YP series variable frequency special motor can be equipped with brake and encoder, which can achieve accurate parking and high-precision speed control through speed closed-loop control.
The precise control of ultra-low speed stepless speed regulation is realized by using “reducer + frequency conversion special motor + encoder + frequency converter”. YP series frequency conversion special motor has good universality, its installation size conforms to IEC standard, and has interchangeability with general standard motor.
3、 Frequency conversion motor wiring
R. S, t for input, u, V, w for output! If the motor needs to be converted to power frequency operation, then the U, V and W phase sequence of frequency conversion output must be consistent with the U, V and W phase sequence of power frequency input!
The return circuit of motor frequency converter is mainly as follows: R, s and t ports are the input ports of power supply, and the output ports of frequency converter are u, V and W, which are connected to the motor respectively. When we are used to the forward rotation of the motor frequency converter, we first connect the intermediate relay and the motor to the control input common terminal. At this time, the forward rotation starts, and the normally open contact of the intermediate relay gets power because it is closed. At this time, the motor is rotating forward. If the current is lost, the motor will stop.
In the whole wiring process of motor frequency converter, of course, it is necessary to set the parameters of frequency converter. We need to set the frequency and operation mode of frequency converter. In addition to these basic settings, we also need to set the maximum frequency and basic frequency of current. The rated voltage, maximum output voltage and related time can be changed at the same time, Finally, there are some functions such as data protection, function code LCE monitoring, starting frequency holding time and so on, which can be set according to the inverter type of different manufacturers.
*1. There is wiring protection at the input side (primary side) of frequency converter. Therefore, please install MCCB or ELCB (with over-current protection function) recommended by each frequency converter. Do not use circuit breakers with recommended power above.
*2mccb or ELCB is used to separate the frequency converter from another power supply. Therefore, please set the recommended electromagnetic contactor (MC) on each frequency converter as required. In addition, when MC or solenoid coils are set near the frequency converter, please connect them with surge absorber in parallel.
*3. Even if the main power supply of the inverter is cut off, if you want to keep the overall alarm signal when the protection function is working together, or if you want the operation panel to display, please connect this terminal to the power supply. Even if the power input is not provided to the terminal, the inverter can operate.
*4 usually no connection is required. High power factor power supply inductive PWM converter: used in combination with RHC series (hereinafter referred to as PWM converter).
*5 when connecting the DC reactor (DCR) option, please remove the short-circuit bar between terminals p1-p (+) before connecting.
*When the output power of the applicable motor is more than 75kW, be sure to connect the DC reactor (DCR) option. In addition, when the power of the power transformer is more than 500KVA, and is more than 10 times of the rated power of the inverter, and when the same power system “has semiconductor load”, please connect the DC reactor (DCR)
*7 a built-in braking resistor is connected between the terminals P (+) – dB of the frequency converter below 7.5kW. Be sure to remove the connection of the built-in brake resistor when the external brake resistor (option) is connected.
*8 is the terminal for motor grounding. Please connect as needed.
*9 in the control signal line, please use twisted pair or shielded wire. Please ground the shield wire. In order to prevent misoperation caused by noise, please separate it from the main circuit wiring as far as possible, and do not put it into the same cable trough（ The recommended distance is more than 10 cm.) When crossing occurs, please cross the main circuit wiring vertically as far as possible.
*The functions recorded in terminals FWD, rev and x1-x9 (digital input), terminals y1-y4 (transistor output), terminals y5a / C and 30A / B / C (contact output) show the functions given in the factory.
*11 is the switch connector of the main circuit. Please refer to the instruction manual for details.
*12 is to control all kinds of switch on the printed circuit board, which can set the action of frequency converter.