The Application of FD5000 in Water Treatment Plants

The water pump is the core equipment in the water supply process of a water plant. The traditional method of directly driving the pump by the power grid has problems such as large starting current, inconvenient adjustment of water pressure and flow, high energy consumption, and the potential to cause harmonic pollution to the power grid. These issues have long plagued the operation of the water plant.

With the development of high-voltage variable frequency speed regulation technology, the method of using variable frequency to drive water pumps has gradually replaced the traditional method and has become the preferred choice for upgrading and transforming equipment in water plants. A certain water plant in a foreign country has a very high daily water production capacity. There are various application methods for variable speed regulation of water pump motors. For its previous pump machines, this company selected a certain foreign brand of high-voltage frequency converter to achieve variable frequency speed regulation. Now, in order to reduce procurement costs, it requires that the functional performance be consistent with that of ABB's frequency converter. It intends to carry out variable frequency speed regulation transformation and upgrading of the existing new water pumps.

Implementation Plan

To match the customer's new water pump, the FD5000-6/1000F-1A model of high-pressure frequency converter was selected. The basic parameters of this model frequency converter are as follows:

The secondary winding of the phase-shifting transformer (H-class insulation) of the FD5000 series high-voltage inverter is the input of the power unit; each power unit bears the full current, which is 1/5 of the phase voltage and 1/15 of the output power. Each of the 15 units has its own input winding, thus achieving insulation. The extended delta connection of the secondary winding is for multiplexing and reducing the harmonic of the input current. The 15 secondary windings are divided into three phase groups. The secondary winding of the phase-shifting transformer is divided into three groups, achieving 30-pulse rectification, the harmonics of the input current waveform are suppressed, and the value of the load power factor is close to 1. After measurement, the total harmonic content of the input current is less than 4%.

The secondary windings of the transformer are insulated from each other, so the main circuit of the power unit is relatively independent. Its structure is similar to a low-voltage inverter and adopts mature technology.

Application advantages

1. Soft start speed regulation: The pump speed adjustment is smooth and reliable, with a gentle increase and decrease in speed. This improves the starting current and mechanical shock of the unit, and allows for flexible speed adjustment to meet the process requirements of different water supply pressures and flows in the water plant.

2. Easy automation: The device is equipped with a 10-inch touch screen, multiple digital quantity terminals, analog quantity terminals, and various communication interfaces. It can be linked with industrial control PCs and water plant dispatching systems to achieve local/remote monitoring functions.

3. Strong grid adaptability: Ensures the stability of output voltage, current, and speed.

4. Speed start: During operation, a sudden loss of high voltage power can be restored within 3 seconds, and the high-voltage frequency converter will not stop. After the high voltage is restored, the frequency converter will automatically run to the frequency before the power loss.

5. Flywheel start function: It can identify the motor speed and directly start when the motor continues to rotate.