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This post was last edited by Wang Tianze on 2015-12-6 at 20:58. 65. A certain process requires a measurement range of 0–300°C, with a maximum absolute error of no more than ±4°C; the selected precision level is (B.1.0). A. 0.5 B. 1.0 C. 1.5 D. 4.066. In a three-phase power supply system with an ungrounded neutral point, in order to prevent electric shock, it is necessary to ensure a reliable connection between the metal casing or framework that insulates the live parts of electrical equipment and the ground; this is referred to as (D. protective grounding). A. Working ground connection B. Working neutral connection C. Protective ground connection D. Protective neutral connection 67. The power of an asynchronous motor does not exceed (B. 10 kW), and it can generally be started directly. A. 5kW B. 10kW C. 15kW D. 12 kW 68. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its scale; if it is below 1/3, then (C. the relative error increases). A. The instrument does not indicate anything due to too low pressure. B. The accuracy level decreases. C. The relative error increases. D. There is a leak at the weld joint of the pressure gauge; it has been turned off
65. A certain process requires a measurement range of 0–300°C, with a maximum absolute error of no more than ±4°C; the selected precision is (B). 66. In a three-phase power supply system with an ungrounded neutral point, in order to prevent electric shock, ensuring that the metal enclosure or frame that isolates the live parts of electrical equipment from the ground is properly connected to the earth is referred to as (D). 67. The power of asynchronous motors does not exceed (B), and they can generally be started directly. 68. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its scale; if it is below 1/3, then (C).
65. A certain process requires a measurement range of 0–300°C, with a maximum absolute error of no more than ±4°C; the selected precision is (B). A. 0.5 B. 1.0 C. 1.5 D. 4.0 6. In a three-phase power supply system with an ungrounded neutral point, in order to prevent electric shock, it is necessary to ensure a reliable connection between the metal casing or framework that insulates the live parts of electrical equipment and the ground; this is referred to as (D). A. Working ground connection B. Working neutral connection C. Protective ground connection D. Protective neutral connection 67. The power of an asynchronous motor does not exceed (B); in such cases, direct starting can generally be used. A. 5kW B. 10kW C. 15kW D. 12 kW 68. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its scale; if it is below 1/3, then (C). A. The instrument does not indicate anything due to low pressure. B. The accuracy level decreases. C. The relative error increases. D. There is a leak at the weld joint of the pressure gauge
65. A certain process requires a measurement range of 0–300°C, with a maximum absolute error of no more than ±4°C; the selected precision is (B. 1.0). 66. In a three-phase power supply system with an ungrounded neutral point, in order to prevent electric shock, ensuring that the metal casing or frame that isolates the live parts of electrical equipment from the ground is properly connected to the earth is referred to as (D. Protective grounding). 67. The power of asynchronous motors does not exceed (B. 10kW), and they can generally be started directly. A. 5kW C. 15kW D. 12 kW 68. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its scale; if it is below 1/3, then (C. the relative error increases).
65. A certain process requires a measurement range of 0–300°C, with a maximum absolute error of no more than ±4°C; the selected precision is (B). 66. In a three-phase power supply system with an ungrounded neutral point, in order to prevent electric shock, it is necessary to ensure a reliable connection between the metal casing or frame that insulates the live parts of electrical equipment and the ground; this is referred to as (C). 67. The power of asynchronous motors does not exceed (B), and they can generally be started directly. 68. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its scale; if it is below 1/3, then (C).
Because there is no powered neutral point (for example, in China’s 10KV systems, where ungrounded or low-current grounded systems are commonly used), it is necessary to connect the metal enclosures or frames that insulate electrical equipment from its live parts to the ground as a protective grounding measure
To prevent electrical equipment from posing a risk of electric shock due to insulation damage, connecting the metal casing of the electrical equipment to the neutral point of the power supply transformer is known as protective grounding. Neutral grounding protection (also known as zero connection protection) refers to the practice, in systems where the neutral point is grounded, of establishing a good metallic connection between the metal parts of electrical equipment that are not charged under normal conditions and the neutral wire
65. A certain process requires a measurement range of 0–300°C, with a maximum absolute error of not more than ±4°C; the selected precision is (B). A. 0.5 B. 1.0 C. 1.5 D. 4.0 66. In a three-phase power supply system with an ungrounded neutral point, in order to prevent electric shock, it is necessary to ensure a reliable connection between the metal casing or frame that insulates the live parts of electrical equipment and the ground; this is referred to as (D). A. Working ground connection B. Working neutral connection C. Protective ground connection D. Protective neutral connection 67. The power of an asynchronous motor does not exceed (B); in such cases, direct starting can generally be used. A. 5kW B. 10kW C. 15kW D. 12 kW 68. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its scale; if it is below 1/3, then (C). A. The instrument does not indicate anything due to low pressure. B. The accuracy level decreases. C. The relative error increases. D. There is a leak at the weld joint of the pressure gauge