SU376854A1 - DEVICE FOR COMPENSATION OF THREE-PHASE VOLTAGE ASYMMETRY - Google Patents

Description

one

When a single-phase or any other asymmetrical load is connected to a three-phase source with a power comparable to the source MOHI, the three-phase voltage system distorts the source output because the asymmetrical current of the load creates asymmetrical voltage drops on the internal resistance of the source. Such a phenomenon occurs, for example, when a single-phase traction load is supplied from a three-phase power supply system.

Asymmetry of a three-phase voltage has a detrimental effect on a three-phase load (e.g., asynchronous motors) that are supplied from the same source (power system) in parallel with a single-phase (asymmetrical) load.

Devices for compensating three-phase unbalanced voltage at single phase loading are known, containing longitudinal compensating co-locators and transformers.

The aim of the invention is to compensate for the incomplete three-phase voltage metric when the three-phase load is powered from the winding of the low-voltage transformer connected by a star, and single-phase from the winding connected by a triangle.

The goal is achieved by the fact that the transformers are made with three windings, with the first windings of the transformers connected in parallel to the condeitor. The second ones are included: -. respectively, respectively, in the same phase of the three-phase load, and the third encounters about the third phase of the three-phase impedance.

In the drawing there is a device for compensating for a three-phase voltage. It contains two longitudinal compensating capacitances Ci and C2, which are included in

The two phases of the line supplying single-phase loads are magnetically connected by means of three-winding transformers with linear three-phase loading, the windings 3 and 4 being included according to the same phases, and

5 n 6 - counter to the third phase of a three-phase load (for a transformer with connection group N ° 11). For the transformer with the connection group No. 1, the difference is that the windings of the consonant inclusion 3 and 4 include

successively in the second phase of a three-phase load, winding 5 - counter to the third phase, and winding 5 - counter to the first phase of the three-phase load.

The value of each compensating resistance is determined by the formula:

 ZK / -iso

V 3

where ZK is the short-circuit resistance of the power supply system at the terminals of the step-down transformer.

Since the phase angle ZK is usually close to 60 °, Z is of capacitive nature, and the magnitude of each capacitance is determined by the formula:

Have

C (j,) ZK

The transformation ratios of the coupling transformer must be equal to the phase ratio between the respective secondary windings of the step-down transformer, i.e.

W, W: Wy WzWA

Ws WsW W ,, W7-A

In order to avoid the occurrence of resonance phenomena, the coupling transformers must be calculated and the maximum possible voltage lyz where is the 1st current setting of the overcurrent protection of the imitating system.

Prevention and Consideration

A device for comparing three-phase voltage imbalance under single-phase load, containing longitudinal compensating capacitors and transformers, characterized in that. in order to maintain symmetry trehfaziogo iapr voltage when the three-phase fed with the load of winding reducers transformer, wye, a single phase - from winding connected triangle capacitors are installed in two phases IITA network and ukazaiiye transformers vypolieny with three windings, the first traisformatorov winding are connected in parallel to the coidisation device, the second ones are in accordance with, respectively, in the same phases of the three-phase load, and the third are counter to the third phase of the three-phase load, the Priority and Numbers range from March 16, 1970

 / -v