Comparison between high voltage soft starter and low voltage soft starter, Yuanchuang electric

  Comparison between high voltage soft starter and low voltage soft starter, Yuanchuang electric
Comparative analysis of high-voltage soft starter and low-voltage soft starter the main circuit of soft starter adopts thyristor, and the voltage is raised by gradually changing the conduction angle of thyristor to complete the starting process, which is the basic principle of soft starter
In the low-voltage soft starter market, there are many products, but there are still few high-voltage soft starter products
The basic principle of high-voltage soft starter is the same as that of low-voltage soft starter, but there are the following differences between high-voltage soft starter and low-voltage soft starter: (1) when high-voltage soft starter works in high-voltage environment, the insulation performance of various electrical components must be better, and the anti-interference ability of electronic chip is stronger
When the high-voltage soft starter forms the electrical cabinet, the layout of electrical components and the connection with the high-voltage soft starter and other electrical equipment are also very important
(2) High voltage soft starter must have a high-performance control core, which can process the signal timely and quickly
Therefore, this control core generally adopts high-performance DSP chip, rather than the ordinary single chip microcomputer core of low-voltage soft starter
The main circuit of low-voltage soft starter is composed of three groups of anti parallel thyristors
In the high-voltage soft starter, because the withstand voltage capacity of a single high-voltage thyristor is not enough, it must be divided by multiple high-voltage thyristors in series
However, the performance parameters of each thyristor are not completely consistent
The inconsistency of thyristor parameters will lead to the inconsistency of thyristor opening time, resulting in the damage of thyristor
Therefore, in the selection of thyristors, the thyristor parameters of each phase must be consistent as much as possible, and the element parameters of RC filter circuit of each phase thyristor must be consistent as much as possible
(3) The working environment of high-voltage soft starter is vulnerable to various electromagnetic interference, so the transmission of trigger signal must be safe and reliable
In the high-voltage soft starter, the trigger signal is transmitted by optical fiber, which can effectively avoid all kinds of electromagnetic interference
There are also two ways to transmit signals through optical fibers: a multi optical fiber mode and a single optical fiber mode
Multi optical fiber mode, that is, each trigger board has one optical fiber; Single optical fiber mode means that there is only one optical fiber in each phase, and the signal is transmitted to a main trigger board, which is then transmitted to other trigger boards in the same phase
Since the loss of each optical fiber is not consistent in the photoelectric transmission process, from the perspective of trigger consistency, the mode of single optical fiber is more reliable than that of multiple optical fibers
(4) High voltage soft starter has higher requirements for signal detection than low voltage soft starter
There are a lot of electromagnetic interference in the environment where the high-voltage soft starter is located, and the vacuum contactor and vacuum circuit breaker used in the high-voltage soft starter will produce a lot of electromagnetic interference in the process of opening and closing
Therefore, the detected signal should be filtered not only by hardware, but also by software to remove the interference signal
(5) After the soft starter completes the startup process, it is necessary to switch to the bypass operation state
How to smoothly switch to the operation state is also a difficulty of the soft starter
How to select the correct bypass point is very important
The bypass point is early and the current impact is very large
Even under low voltage conditions, it will cause the circuit breaker in the three-phase power supply to trip and even damage the circuit breaker
It is more harmful under high pressure
The bypass point is late and the motor shakes badly, affecting the normal operation of the load
Therefore, the hardware detection circuit of bypass signal must be very accurate, and the program processing must be appropriate