SERVICE HOTLINE1. What are the single and four quadrants?
The rectangular coordinate system established with the speed of the motor as the longitudinal coordinate axis and the torque as the transverse coordinate axis is used to describe four operating states of the motor, namely, forward electric, feedback generating braking, reverse braking and reverse electric. The mechanical characteristic curves of each state are respectively in the four quadrants of the rectangular coordinate system. If the device can only satisfy the motor's electric operation state, then it is one-quadrant. If the device drive in the electric state, can from the electric state into the second quadrant operation, can also from the electric state into the fourth quadrant operation, then the device is four-quadrant. The single quadrant device can only be forward electric or reverse electric, and cannot enter the regenerative power generation operation from electric operation.
2, about the controller quadrant and motor quadrant:
Single quadrant: Energy can only flow in one direction.
Four quadrants: Energy flows in both directions.
Motor and frequency converter have their own quadrants, don't get confused.
* Single quadrant operation of the motor refers to the electric operation of the motor. The four quadrants are power generation operations.
* Single quadrant operation of frequency converter, referring to energy from the grid into the frequency converter. Four quadrants means that energy can be fed back into the grid.
This may be the case:
a. Inverter with single quadrant operation and motor with four quadrant operation. The energy generated by the motor increases the bus voltage, or is consumed in the brake cell.
b. Single-quadrant DC speed regulation reversing trouble, need to change the excitation or armature positive and negative to achieve reversal.
Four quadrant DC speed regulation has two sets of rectifier bridge, the output direction is opposite, one set of work when the positive turn, the other set of work when the reverse.
The main thing to pay attention to is the time of reversing:
For a single quadrant governor, when the motor needs to reverse, to add a time relay. Whether changing the direction of excitation or changing the direction of armature, it must wait for a period of time, that is to say, it is not allowed to suddenly change direction during work. Because the excitation coil and armature coil are both direct current, it takes time to release the energy. If the commutation is too fast, the rectifier bridge will reverse breakdown. The four-quadrant governor does not have this problem, because the two sets of rectifier Bridges are in opposite directions. When one group stops output, the other group can just release energy to the motor.
3. Exchange of frequency converter and DC governor:
Theoretically speaking, the AC motor frequency conversion device controlled by the magnetic field vector can completely replace the DC speed regulation system, of course, to achieve 4 quadrant operation, IGBT and rectifier diode should be inverted parallel, in order to achieve the reverse of the current. Motor is also required to have speed feedback, such as tachometer generator or code plate, but also according to the characteristics of the load, choose the constant torque and constant power of the motor speed range.
4. How to realize the 4 quadrant drive function of frequency converter?
The use of British CT Unidriver series AC drive, as well as ABB, Siemens inverter can realize the four-quadrant drive function. When used, the motor should be replaced by AC motor, and at the same time, the inverter should be equipped with energy consumption unit. There are two ways to choose.
(1) The braking unit + braking resistance is used to consume the direction regeneration current generated when the motor is reversed, otherwise it is easy to burn the frequency converter or cause the frequency converter to trip.
The inverter is connected to the DC bus of the converter. When the direction regeneration current is generated, the voltage of the DC bus of the converter is increased. The DC high voltage of the DC bus is changed into the AC power synchronous with the AC power grid through the inverter
Feed back to the power grid, realizing the role of energy saving. This mode is often used for multiple high-power variable frequency drives.
5. Operation of DC motor transmission equipment in 4 quadrants:
When the radius of the coil is small, the moment arm is short, the torque is small and the speed of the motor is high. When the radius of the coil is large, the moment arm is long, the torque is large, and the speed of the motor is low. This can also realize the constant speed of the winding line. Of course, the radius of the coil should be detected. For such a constant power load, I think we should choose a motor with small base speed (that is, the speed corresponding to the highest voltage of the stator), and a larger speed range for weak magnetic rise, so as to give full play to the motor's efficiency.
Similarly, the frequency conversion speed regulation of AC asynchronous motor also has the base speed up and down, but the base speed is frequency conversion voltage change (φ constant) constant torque speed regulation; Above the base speed is constant voltage frequency rise (φ decreases) constant power speed regulation.
