Definition :Neutral ungrounded power distribution system
Unit :International Electrotechnical Association
Standard :IEC60364 standard
"Medical isolated power supply system"
Introduction of medical
Medical field choose IT system:
(IT system, i.e. neutral ungrounded power distribution system)
1. The necessity of choosing IT system in medical field:
(IT system, i.e. neutral ungrounded power distribution system)
1. IT system reduces the contact voltage and the leakage current of the grid to the ground (effectively controlling the direct leakage current to the heart), so the danger of personal electrocution is minimized;
It is well known that, when the leakage of the electric equipment to the heart is greater than 10uA, it will cause the danger to the heart of human beings. 10uA, will cause the patient's microelectric shock injury. In general, the general building used in the RCD, ELCB and other earth leakage protection switch, its action response value is mA level (such as: 30 mA), far from meeting the needs of the medical field.
Therefore, now the international medical field in the operating room, ICU, CCU and other important places usually use local "neutral ungrounded power supply system" (i.e., "IT system" or "isolated power system") power supply. Power supply system"). The single-phase 3KVA-10KVA medical isolated power supply to these places can firstly prevent the leakage current in other power supply circuits from escaping into the medical electrical equipment in operating rooms, ICUs and CCUs through the grounding wire, which poses a threat to the safety of the patients; in addition, once the loads connected to the isolated power supply (e.g., all kinds of medical electrical equipment) have a fault to the ground, it will only produce a very small capacitive leakage current due to the fact that it cannot form a circuit to the ground, which can only produce a small capacitive leakage current. In addition, once the load connected to the isolated power supply (such as various medical electrical equipment) has a fault to ground, it can only generate a very small capacitive leakage current because it cannot form a circuit to ground, which greatly protects the patient from leakage current.
2. When the first insulation fault occurs on the load side of the grid, it will not cause the power supply open action (trip),
ensuring the continuity of the power supply;
In the medical field, some places have very high requirements for the continuity of the power supply, so it is designed as two (or even three) power supply (grounding power supply system) automatic switching to ensure that the continuity of power supply in these special places. However, if a relative insulation fault occurs at the load end, the fault current will pass through the neutral point of the power supply to the ground to form a circuit, thus forming a large fault current, which will cause the upper level air switch or fuse to operate, and ultimately lead to the interruption of power supply. If these special places in the local use of IT power distribution system, because of its power neutral point is not grounded, when the load side of a relative insulation failure, because it can not constitute a circuit to ground, will only produce a very small capacitive leakage current, will not be harmful to the human body, at the same time will not lead to the action of the air openings to ensure that the power supply of the operating room connectivity.
3. Reduce the leakage current to ground, so improve the fire safety.
4.