anode saturable reactors are used in converter valves of hvdc converter stations. the main function are the following: first, it is used to limit the rapid current rising rate (di/dt) in the valve and avoid thyristor element burning caused by the inrush current when thyristor elements are connected; secondly, it is used to avoid thyristor open caused by the inrush voltage with a rapid voltage rising rate (du/dt) when the thyristor elements are disconnected.
when the thyristors are on and the current is starting to rise, the anode saturable reactor has a very high impendence to limit the current rise; once the thyristors have enough carriers, the reactor shows a low impendence feature, which helps to decrease the reactance and increase the converter valve efficiency. therefore the design of the anode saturable reactor must have the non-linear saturation core feature.
product feature specification:
1）anode saturable reactor used in the hvdc converter device
due to the special using environment, the requirement on the reliability of the electrical components is extremely high. reliability is the main criteria when choosing components and materials and our main focus when designing the product. other important criteria are impulse feature, layer insulation, inrush current tolerant capability, temperature rise and partial discharge. this is why we use the following items in our design: highly insulated self-cooling coils, thin cold rolled silicon steel with high permeability, external shell with high mechanical strength and dielectric strength. all these items plus the casting resin sealing structure significantly decrease the noise and increase the inrush current tolerance capability. the reactor has a nice appearance and structure.
2）confirm the key components of the product
the method of choosing the key components is based on the product features and the impact on the product’s main functions. this includes product reliability, safety, lifetime and cost. the product comprises the following key components: aluminum cable, iron-core, gap piece, casting material, and external cover. the anode saturable reactor falls into the category of iron-core type. the use of converter valves requires that the reactors need to fulfill electrical performance requirements on one hand, and be able to fit in the working environment of the converter valves on the other hand. this kind of reactor provides high electrical quality, fast dynamic response, fire resistance, compatible structure, easy assembly, light weight etc. therefore, we have adopted various materials with first-class performances inchinain designing our anode saturable reactors and solid test results have proved that these materials are totally capable of meeting the requirements of valve reactors.
3）shockproof and noise reduction technologies
reactors tend to produce loud noises while in use, which is a common disadvantage for iron-core type reactors with air gap. and this is the main source of noises in the converter valves. our reactor design has considered this point. we use a special elastic material to cast the reactor coils and the core as a whole in order to fix their positions and reduce the noise.