Purpose of the brushless excitation system of the SVBG
The brushless excitation system of the SVBG series is designed to replace electrical excitation systems for hydro generators with a capacity of 1.0 to 150 MW during their reconstruction, as well as during new construction.
Composition
The brushless excitation system includes:
- brushless diode exciter;
- excitation control cabinet;
- a transformer (a group of transformers).
BRUSHLESS EXCITER
The brushless exciter is a synchronous reversed generator, the AC winding of which is located on the rotor, and the excitation winding on the stator. The anchor of the exciter through a rotating diode rectifier is rigidly connected to the excitation winding of the hydro generator. Regulation of excitation of the generator is carried out by regulating the excitation current of the exciter.
The new brushless exciter, as a rule, has the same dimensions as the replaced electric DC exciter. At the same time, it is advisable to preserve power contact rings on which tires or cables can be connected from direct current terminals of the rotating rectifier of the brushless exciter. This method of reconstruction is relative to roads, since it requires the design development and manufacture of a new exciter in the conditions of an electrical engineering enterprise.
General view of the anchor of the brushless exciter. Cascade of Kuban HPPs
We have developed a method of reconstruction based on the conversion of a regular exciter into a brushless one.
In this case, the existing anchor winding is switched to malternating-current phase winding with n-parallel branches in each phase. A rotating diode rectifier shall be installed in place of the collector.
As a rule, the condition of insulation of the anchor winding is quite satisfactory and only re-insulation of individual sections may be required. In industrial conditions, the circuits of connecting the winding with a “star” and the so-called closed ring windings have been tested, requiring a much smaller amount of work on the transformation of the exciter.
The rotating diode rectifier is performed according to the bridge scheme with the number of diodes in the shoulder equal to the number of parallel branches of the anchor winding. Special rotary diodes of the D105-630 type of 24-28 class are used. Additional poles are removed from the magnetic system of the exciter. If necessary, a third power contact ring is installed in the generator rotor circuit.
A patent was obtained for the proposed method of reconstruction of the electromagnetic excitation system.
EXCITEMENT CONTROL ROOM
To control the excitation of the exciter, and, consequently, the generator, the excitation control cabinet of the SHUV series is used.
General view of the excitation control cabinet in a two-channel version of the SHUV-2K-63-115 UHL4 type for a 23.5 MW hydro generator of the Pazsky HPP Cascade
Control cabinets are available with one or two independent converter-regulatory channels, that is, in the latter case, 100% hot reserve is provided.
Each channel includes a microprocessor automatic excitation regulator containing a power transistor transducer and the necessary switching, protective and control and measuring equipment.
The regulator software implements all the functions of control, regulation, protection, diagnosis and signaling about the state of the excitation system. Transitions from channel to channel are carried out automatically in the event of any malfunction that interferes with the performance of its functions, or at the command of the operator.
Each channel can be powered: from the outputs of the generator, from the terminals of the rotor through the power contact rings and from the network of own AC needs. Initial excitation is carried out from the direct current network.
The company performs works on the transformation of the exciter, chief installation and commissioning works, comprehensive tests of the excitation system together with the generator, training of service personnel, warranty and post-warranty service, technical advice. Work is carried out in terms of 3 to 6 months, depending on the terms of payment and the readiness of the station equipment for dismantling and installation work.