For bircuit breaker:
Principles for type selection of contactor
Principles for type selection of thermal relay
Principles for type selection of voltage stabilizer
Principles for type selection of isolator and knife switch
Principles for type selection of transducer options
1. AC input reactor or DC reactor (for civil use) shall be selected for the following conditions:
– If not used for a power supply(central air-conditioner motor of a hotel) greater than 55KW and poor power grid or conditions with relative small capacity, it may cause interference and excessively large deviation of three-phase current, and frequent transducer burnout.
– The distance between a motor and a transducer is greater than 100m.
2. Braking unit and braking resistor shall be selected for the following conditions
– The load is being limited.
– Rapid acceleration and deceleration frequently.
– Large inertia(a device that needs more than 1 minute for free stopping and for which constant-speed operation is smaller than accelerating current).
Principles for type selection of rated current of general fuse
How are residual current devices classified, according to action features when residual current is with direct current component?
What is the difference between NB1 and eB?
Different breaking capacity
NB1 can indicate the status of contact, but eB can’t.
Braking unit of NB1 is specially designed, very convenient for customer. If an individual product fails and a bus-bar is used for connection, you only need to disassemble the failed product, other than all these devices surrounding the failed one.
What is the difference between NVF2 and NVF1?
What is the difference among NM1, NM7 and NM8?
For NM7 and NM8, the common point is that the accessories of them both are modularized in installation, while they are different in the following aspects:
What are the accessories available for NA1-2000?
What are the accessories available for NB1-63?
What are the accessories available for DZ158-125?
AX-1 Auxiliary contact
What are the accessories available for NC1?
What are the accessories available for NC8?
What are the accessories available for NS2?
What are the accessories available for NM8?
Maintenance and overhaul of NA1 air circuit breaker
Maintenance of circuit breaker (at least once half a year):
Inspection and repair of circuit breaker (at least once a year):
Installation, use and maintenance of NM8 series plastic shell circuit breaker
Use and maintenance: (only persons with corresponding electrical professional qualifications permitted)
Safety notes for NJR2 soft starter
Safety notes for NVF2 transducer
Notes for power transformer: major components
What is the function of transformer oil?
Transformer oil is used for insulation and cooling;
And for arc blowout in on-load tap changer;
What is the function of oil conserver?
Oil conserver is used to regulate the oil level, so that the transformer oil tank is always fully filled;
And to reduce the area of the contact surface between oil and air, so that oil will not be damped or oxidized at a very fast speed.
What is the function of transformer bushing? what are the requirements for it?
The function of transformer bushing is as follows:
It leads the high-voltage and low-voltage wire leads inside the transformer to outside the oil tank; it insulates the leads against the ground and fixed the leads. Transformer bushing is one of the current-carrying components of transformer. It conducts load current for long in the transformer operation and conducts short-circuit current when short circuit occurs outside the transformer.
The requirements for transformer bushing are as follows:
What are the two types of transformer test items? What are their contents?
Transformer test is generally divided into insulation test and performance test.
Insulation test includes insulation resistance and absorption ratio test, dielectric loss tangent value test, leakage current test, transformer oil test, industrial frequency withstand voltage and induction withstand voltage test; local discharge test is required for a transformer with Um of no less than 220kV. Full wave and operating wave impact test is required for online terminal with Um of no less than 300kV.
Performance test includes tests of transformation ratio, wiring group, DC resistance, idle load, short circuit, temperature rise and sudden short circuit.
What is the purpose of DC resistance test of transformer?
The purpose of DC resistance test is to check whether there is short circuit, open circuit or wrong connection in winding loop, whether there are poor contacts in welding point of winding loop wire, lead wire bushing and tapping switch. Besides, it can be checked whether the lead wire used for winding meets the design requirements.
What is the purpose of idle load test of transformer?
The purpose of idle load test is to test the no-load current and no-load loss in iron core, find partial or total defects in the magnetic circuit, and check whether winding has turn-to-turn fault after induction withstand voltage test of transformer.
Why does transformer winding need to be dried?
The purpose of drying is to improve the insulation level of winding. Insulating cardboard can be compressed under certain pressure F, and the mechanical strength of the winding will be improved.
What are the commonly-used insulation materials of Grade A? What is the heat-resistant temperature?
Commonly-used insulation materials of Grade A for transformer are insulating cardboard, cable paper, yellow painted silk, phenolic cardboard, wood and transformer oil, etc.
Heat-resistant temperature is 105℃.
Why does vacuum drying transformer have better effect?
Under vacuum condition, the higher the vacuum degree is , the lower the boiling point of the water molecules will be; and heated water is easily evaporated. The water volatilized from the transformer is rapidly drawn out by vacuum pump, thereby speeding up the evaporation of water, so this method has a good effect.
What are the requirements for parallel running of transformers? What are the consequences if they are not met?
The parallel running of transformers should meet the following conditions:
If they are not met, the consequences are:
What measures should be taken for open core hanging of transformer?
Open core hanging should be conducted in fine weather and the relative air humidity should be lower than 75%. The part of core exposed in the air should be lower than 12h when the relative air humidity is lower than 75%. Core of no more than 16h can be exposed if the relative air humidity is lower than 65%. Effective measures should be taken to prevent dust and rain from the transformer. If the ambient temperature is higher than the core temperature, leave the core resting f the ambient temperature or a while before hanging it out, or heat the core to 10℃ higher than the ambient temperature when necessary.
What are the main equipment and materials used in the transformer core hanging?
What foreign certification does the company have received?
Part of the company's products have passed:
Which products have UL certification, accreditation, or are listed?
NC1/CJX2, NC6, NC8, NC2, NCK3, NCK5, NR2, NRE8, NS2-25, ND16, NP2/NP4, JQX-10F, JQX-13F, NJX-13FW, JZX-22F, JSZ3, NJS1, KG10D/KG10M, XJ3, NJB1,NB1-63,CB-125,YBLX-P1.
Which products have KEMA certification?
NC1, NC7, NC8, NM1, NM7, NM8, NA1, NA8G, NR2, NP2, NBH8-40, NB1L, Ex9CBL-N/Ex9CBL-H, NZ7, NH40, MES(BH-0.66), 138kV 45MVA transformer, 230kV 45MVA transformer, 230kV 250MVA transformer, 145kV GIS, 24kV Switchgear Panel, NV Series Indoor Vacuum Circuit Breaker.
Which products have CESI certification?
230kV 45MVA transformer, 150kV 80MVA transformer, 132kV 40MVA transformer.
Which products have DNV marine certification?
What international standards do products of the company comply with?
Miniature circuit breaker
IEC/EN 60898-1, IEC/EN 60947-2
Moulded case circuit breaker
Air circuit breaker
Automatic change-over switch
IEC 60076, IEEE, ANSI, AS
SF6 Circuit Breaker
IEC 62271-200, IEC 60420
IEC 60439-1, IEC 61204-2001, IEC 60255
IEC 60044-1, IEC 60044-2, IEC 60044-3, IEC 60044-5
What is the difference between UL certification, UL accreditation and UL listing?
UL certification adopts American standards, and the product performance only covers North America and Japan, etc, and it is not applicable to Europe and other regions.
UL accreditation adopts all kinds of corporate standards, IEC international standards or European standards; the performance of their products has a larger coverage including China.
UL listing only applies to complete products and all kinds of parts or devices replaced or installed on site by qualified personnel. Products that apply to UL listing service include household appliances, medical equipment, computers, commercial equipment, as well as the various types of electrical products in construction, such as such as power distribution systems, fuses, wires, switches and other electrical components. A UL Listed product generally has UL Listing mark on it.
What are the common reasons why NA1 breaker cannot be closed?
Drawer-type circuit breaker cannot be rocked to the “connection" position; what is the cause?
what are the common causes for contactor noise?
What are the common causes for damage to the contactor coil?
What are the common causes for thermal relay malfunction?
Main causes for and solution to the malfunction of residual current circuit breaker:
1. Operating current is selected too small;
When selecting operating current, it should be higher than 2-4 times normal leakage current in circuit. If normal leakage current of the electronic equipment is larger, the equipment on each circuit cannot be too many, and the total leakage current should be lower than the rated non-operating current of RCD. For example, the leakage current of a desktop computer is 3-4mA, so the number of computers connected to 30mA RCD circuit should not be more than five.
2. Improper use of residual current circuit breaker may cause malfunction;
When a three-pole earth residual current circuit breaker is used in a three-phase four-wire circuit, as the normal operating current in neutral line does not go through zero sequence current transformer, residual current circuit breaker will action once single-phase load is started.
Solution: A three-pole four-wire or four-pole residual current circuit breaker must be used for a three-phase four-wire circuit.
3. Grounding of load-side neutral line behind the residual current circuit breaker causes malfunction;
Grounding of load-side neutral line of the residual current circuit breaker will lead normal operating current to the ground through the grounding point, causing malfunction of residual current circuit breaker.
Solution: Connect the grounding wire to the neutral line on the power side of residual current circuit breaker.
4. Leakage current and wire-to-ground capacitive current cause malfunction.
The load-side wire of residual current circuit breaker is long and is laid closely to the ground, and there will be heavy wire-to-ground capacitive current, which may cause malfunction. Or the earth leakage current may be heavy due to decreased insulation of load-side wire, causing malfunction.
Solution: Use residual current circuit breaker with high leakage operating current or raise the wires overhead
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