Mday‘s SPD Purchase Suggestion

Basic composition

The surge protection device ( SPD ) consists of a base, a remote signaling and a pluggable module, which is composed of an optical lifetime status indication and a MOV.  The main function in limiting transient overvoltage is MOV, which are divided into gas discharge tubes, semiconductor discharge tubes, varistors and transient suppression diodes.  Our company mainly makes varistors with a response speed of nanosecond and a circulation capacity between 100A and 100kA. It is mainly used in the fields of power supply system and low-frequency circuit, and MOV has low cost and fast aging speed, so it has a large market demand.  However, fast aging speed is not the same as low safety, which is caused by the great transient overvoltage that can be withstood, and the internal disconnecting device and surge circuit breaker installed in the surge protection device ensure that SPD will not affect the distribution system in case of thermal collapse.

MOV and its structural advantages

Mday MOV have an advantage over other MOV on the market because we combine AC surge protection with DC surge protection.  However, because the impact of DC surge on the MOV is greater than that of AC surge, in order to ensure that this kind of structure can withstand DC surge impact, this kind of MOV has undergone strict 1000 hours DC surge impact test, which not only means that this MOV has a wider utilization range and higher utilization rate, but also means that its service life is longer and its quality is better.

Structure

There is no difference in core MOV of the products operated by our company, but there are differences in internal structure of surge protection device ( SPD ), mainly including OBO structure and DENH structure ( MD, MY ).

According to our understanding of MOV structure, DENH-shaped structures are safer and more reliable than OBO-shaped structures.

• The DENH structure has a specified assembly position, which is more rigorous in assembly and better in safety, while the OBO-shaped structure relies on pouring to fix the MOV, which easily leads to the safety problem of irregular MOV position and cheating on workmanship and materials' business reputation.  Our company adheres to the concept of integrity and safety, and advocates DENH design.
• After the OBO-shaped structure is tripped, the tin sheet is too close to the MOV corner, and even if it is tripped, there is still a great risk of spontaneous combustion, while the DENH-shaped design has a longer tripping distance and adopts plastic baffle design, so the risk is smaller.
• The spring of DENH structure has better quality, faster effect and larger amplitude when tripping, and higher fault tolerance rate, while the spring of OBO structure bears great responsibility in the accident of " spontaneous combustion after tripping".
• Compared with OBO-shaped structure, DENH design uses epoxy resin material for encapsulation, which significantly improves flame retardant performance, enhances heat resistance and thermal stability, and optimizes electrical insulation and heat dissipation performance.

Mday has invested a lot of research in the SPD DENH structure, upgraded and iterated MD series, and launched MY series.

Table 1

MY series		MD series
Configuration of copper parts of base The base is made of copper fittings, which is thicker and thicker. It can bear more current and reduce residual voltage
The impact of the same MOV ( 345431K) is 20 kA, the residual voltage of MD series is 1310 V, and that of MY series is 1187v  It can withstand larger current and reduce residual voltage of surge current, more comprehensive and stable protection equipment
Connection Configuration Hard connection is adopted, which reduces production links and increases reliability compared with copper wire connection, and can realize full automatic production.
Make it more accurate and rapid to prevent spontaneous combustion and fire of products
Configuration of internal structure The internal space of the MOV is larger, and two heat dissipation holes are added to the inner shell, which makes the product have better heat dissipation performance and prepares for compatibility with MOV with larger area (through-flow) in the future
The internal heat dissipation function of the product is improved to make its operation safer, and the internal structure of the MOV is expanded to adapt to the parameter MOV of Datong Flow.
Trip Configuration The spring at the tripping point adopts a spring-back structure: compression rebound is faster than tensile retraction, because the energy transfer is more direct and the loss is less.
Ensure that the product can be tripped in time to protect SPD from burning
Die Configuration The mold is precise, and it can be inserted and unplugged tightly when the buckle is not pinched. It can be easilyremoved when the buckle is pinched, so as to achieve a real buckle-type design and use more high-end materials

MY structure has extremely advanced double-link tripping technology. Point A in the figure is connected with the corner of the MOV. When the limit impulse current that can make SPD spontaneous combustion flows through point A without causing point A to melt, the thinner B end breaks after being impacted by the current, which makes the device trip. The connection of B end is not only a two-stage connection, but also a safety means, which greatly improves the fault tolerance rate of this structure.

Main products

Series	Model	Types	Iimp/ Imax	Products	Image
MY	MYH-DC	T1	5-12.5kA	-	-
	MYH-AC			MYH7-275
	MYN-DC	T2	20-60kA	MYN40-DC
	MYN-AC			-	-
MD	MDH-DC	T1	5-12.5kA	-	-
	MDH-AC			-	-
	MDN-DC	T2	20-60kA	MD-T2-DC
	MDN-AC			-	-