Regulated Electric Drive Mechanism
The regulated electric drive mechanism is an important element used to control an electric drive unit by adjusting its parameters. The working principle of such drives can be described in several stages:
- 1 Stage One: Transformation of single-phase or three-phase input current into direct current using a diode power rectifier.
- 2 Stage Two: Controlling the torque and speed of the electric drive unit's shaft using a frequency converter.
- 3 Stage Three: Managing the output voltage, maintaining a stable U/f ratio.
Selection of Frequency-Controlled Electric Drive
Drive control can be carried out according to various types, such as scalar (for pumps and fans), sensorless and sensor vector, as well as other types. Drives are selected according to the following criteria:
- - type of loads;
- - voltage and nominal value of the drive unit;
- - power of the frequency converter;
- - control mode;
- - frequency adjustment range;
- - reliability specification of electrical components.
If the drive operates in asynchronous mode for extended periods, it is important to choose a frequency converter with high output power.
Technical Features of Using Frequency Electric Drives
- 1. High performance is achieved due to fast switching between modes.
- 2. Most devices are equipped with diagnostic functions, which helps to avoid breakdowns. However, it is important to perform preliminary tuning to prevent unwanted changes from users.
- 3. Regulated drive mechanisms can synchronize conveyor processes or adjust the ratio of different quantities.
- 4. In self-tuning mode, the parameters of the unit are entered into the memory of the frequency converter, which increases the accuracy of torque calculations and improves slip compensation.
Application Area of Frequency Drives
Manufacturers offer various drive mechanisms used in industries where electric switchgear is utilized. Mid-range systems are used in coal-fired power plants, in the mining industry, at elevators, in utilities, etc.
The range of nominal values for drives includes:
- Frequency Converter 2.2 kilowatts;
- Frequency Converter 3 kilowatts;
- Frequency Regulator 37 kilowatts;
- Inverter 4 kilowatts;
- Voltage Regulator 5.5 kilowatts;
- Frequency Speed Controller 75 kilowatts;
- Drive at 11 kilowatts and many others.
Purpose and Technical Features of Frequency Drives
Complex-type drives with a voltage of less than or more than 1 kilowatt are capable of:
- - smoothly starting the drive unit, which reduces its wear;
- - reducing speed, which lowers the rotation frequency of the motor shaft.
Drive cabinets of complex type with a power of up to 1 kilowatt can perform similar functions on engines from 0.55 to 800 kilowatts. The driving mechanism operates normally with a voltage in the network ranging from -15% to +10%. Under continuous operation, power drop is observed at voltages of 85%-65%. The overall power factor is cosj = 0.99.
Advantages of Using Frequency Drives
The use of frequency converters enables the optimization of processes and offers the following advantages:
- - process regulation with increased accuracy;
- - remote diagnostics of the drive mechanism;
- - increase in operating hours;
- - extension of machine service life;
- - significant reduction of acoustic noise from the electric motor.