Electrical safety testing of ME equipment or ME systems is an important part of the protection against electric shock hazard. It is determined by inspection whether the relevant safety or performance parameters of ME equipment or ME system meet the requirements of relevant standards, so that preventive measures are taken to reduce the risk to acceptable. Level. The type test specified in the general standard requires the test items designed for the equipment to be tested to be tested one by one in the appropriate order. Due to space limitations, this section only introduces the main protection requirements for electric shock hazards of ME equipment in the general standard and the corresponding electrical parameter detection methods. . Article 8 of the General Standard relates to the requirements of ME equipment for protection against electric shock hazards, including: basic rules for electric shock protection, requirements related to power supply, classification of application parts, limitation of voltage, current or energy, isolation of components, ME equipment protection grounding, functional grounding and potential equalization, leakage current and patient auxiliary current, insulation, creepage distance and clearance, components and wires, network power supply parts, components and wiring. metal machine shop near me
First, the basic requirements of electric shock protection
1 Overview
Under normal conditions or in a single state, the accessible and applied portions must not exceed the limits specified in the general standard voltage, current or energy limits. Other dangerous conditions in a single fault condition are as follows: injection, deformation of the casing or exceeding the maximum temperature, exceeding the leakage current or the voltage limit of the accessible part including the application part, the specified mechanical hazard, etc. shall not occur. metal machine shop near me
2, normal state
It also includes all of the following:
1) Any voltage or current appearing in any signal output/input section, which is transmitted from other electrical equipment permitted by random files specified in the General Standard, if the random file has no restrictions on these other electrical equipment. The maximum network supply voltage specified by the general standard;
2) For the ME equipment that is expected to be connected to the power supply network through the network power plug, the power supply link is changed:
3) short circuits that do not comply with any or all of the insulation requirements of the general standard;
4) Short-circuits that do not meet any or all of the creepage distances or clearances of the general-purpose standards for creepage distances and clearances;
5) Open circuit that does not comply with the general standards for protective earthing, functional grounding and potential equalization requirements for medical electrical equipment, including any functional ground connections.
Single fault conditions include:
1) Any short-circuit of insulation that meets the requirements of the general standard for insulation protection requirements; NOTE, this also includes short-circuiting of each group of parts that comply with the general requirements for insulation of the double insulation. metal machine shop near me
2) Any short circuit of creepage distance or clearance that meets the general protection measures for creepage distance and clearance requirements;
3) Except for highly-perfect components, any short-circuit or open-circuit of components in parallel with insulation, creepage distance or clearance, unless it can be shown that the short-circuit is not the failure mode of the component;
4) Any open circuit that complies with the general standard for protective earthing, functional grounding and potential equalization requirements of the protective earthing conductor or internal protective earthing connection, but this does not apply to the protective earthing conductor of permanently safe ME equipment, as It is considered impossible to disconnect;
5) interruption of any one of the power supply wires except for the neutral conductor of the multi-phase ME equipment or the permanent installation of the ME equipment;
5) Any one of the power supply wires between the components of the ME device with a discrete enclosure is interrupted if this condition may result in an allowable limit being exceeded;
6) Unintended movement of components;
7) Accidental detachment of wires and connectors where they may cause a dangerous situation after free fall-off. metal machine shop near me
8) Compliance is determined by the application of the specified requirements and the test related to the single fault condition, and the test of the fault determined from the evaluation of the risk analysis results, if any single fault condition is introduced at one time without directly causing the dangerous situation, or any other The result of unacceptable risk is considered to be satisfactory.
3. Testing requirements
The determination of the application part and the accessible part of the general standard determines which parts are accessible. Leakage current is measured according to general standards for leakage current and patient auxiliary current requirements. metal machine shop near me
Second, ME equipment protection grounding, functional grounding and potential grounding
1 Overview
Grounding is an important safety measure for electrical safety. Poor grounding can easily cause electric shock or ME equipment malfunction. The grounding has protective grounding, functional grounding, and potential equalization in three forms. The protective earthing is connected to the protective earthing terminal by a method conforming to the general standard for protection purposes, that is, for the purpose of safety, the protective earthing terminal connected to the conductive part of the class I device is connected to the external protective grounding system through the protective grounding wire. In the ME system, the functional ground can be realized by a functional ground terminal that is accessible to the operator. The functional ground terminal is a terminal that is directly connected to the circuit or a shielded portion that is grounded for functional purposes. Potential equalization is the use of a potential equalization wire to directly connect the electrical equipment to the potential equalization busbar of the electrical device to ensure that several electrical devices forming an ME system have a common reference ground. The equipotential bonding does not assume current (including leakage current). In order to balance the potential difference of the equipment in the local system, the purpose of the protection grounding is to prevent electric shock protection; the purpose of the functional grounding is to shield the interference and stabilize the signal, and the purpose of the potential equalization is to form an equipotential.
2, the scope of use required
The following requirements of Section 318 apply, unless the part considered meets the requirements and tests of IEC60950-1 for protective earthing and is intended as a protective measure for the operator and not for the patient. metal machine shop near me
3, protective ground terminal
1) The protective earthing terminal of the ME equipment shall be suitable for the protective earthing conductor through the power cord and, if appropriate, via an appropriate plug or a fixed protective earthing conductor, to the external protective earthing system.
The fasteners of the protective earthing terminal of the fixed voltage conductor or the power cord shall be fixed so that the internal wiring is not stressed when clamping and loosening the wiring, and the creepage distance and clearance are not reduced to the general standard. Below the specified value.
2) It is not possible to loosen the fastener without the aid of a tool.
3) Compliance is checked by inspection and measurement after clamping or loosening the specified maximum cross-sectional area of the wire 10 times.
4) The screw for the internal protective earthing connection should be completely covered or prevented from loosening from the outside of the ME device. metal machine shop near me
5) If the power input jack of the device is used as the power connection of the ME device, the grounding pin in the power input jack of the device should be regarded as the protective ground terminal.
6) The protective earthing terminal does not apply a mechanical connection between different parts of the ME equipment, or it is used to fix any component that is not related to protective earthing or functional grounding.
7) Compliance is checked by inspection of materials and construction, manual testing and measurement of the specified maximum cross-sectional area of the wire after clamping or loosening 10 times. metal machine shop near me
4. Protective grounding of moving parts
Any protective earth connection cannot be used for moving parts unless the manufacturer proves that the connection remains securely connected within the expected life of the ME unit, and the compliance is checked by inspection of the ME equipment and, if necessary, by checking the risk management documentation.
5, impedance and current carrying capacity
The protective earth connection should be able to reliably carry the fault current without excessive voltage drop. metal machine shop near me
6, surface coating
Conductive parts of ME equipment with weakly conductive coatings such as paint, and for electrical contact between the protective ground connections are important, the coating should be removed at the contact electricity unless inspection of the connection structure and manufacturing process indicates The requirements for impedance and current carrying capacity can be guaranteed without going out of the surface coating.
7, plug and socket
When other personnel other than the service personnel can connect between the power supply network and the ME equipment through the plug and the socket, the protective earth connection should be connected before the power supply ground is turned on, and the power supply connection is broken. It is disconnected after opening. This requirement also applies to protected grounded interchangeable parts. metal machine shop near me
8, potential equalization wire
If the ME device has terminals for powering balanced wire connections, the following requirements apply:
The ME device is in any position for normal use and the secondary terminal should be accessible to the operator;
In normal use, a snap connector should be used to avoid accidental disconnection, or accidental disconnection should not result in an unacceptable risk. metal machine shop near me
The terminal shall allow the wire to be removed without the use of a tool;
This terminal should not be used as a protective ground connection;
The terminal shall be marked with the potential equalization (equal potential) symbol of IEC60417-5021 (DB:2009-02);
The instruction manual shall contain information on the function and use of the potential equalization conductor and shall refer to the requirements of the general standard for medical electrical systems;
The potential equalization leads should not be included in the power supply cord.
9, functional ground terminal
The functional ground terminal of the ME device should not be used to provide a ground connection. metal machine shop near me
10. Class II ME equipment
If an isolated internally shielded Class II ME device is powered by a three-wire power cord, the third drop (connected to the protective earth connection point of the network power plug) should only be used as a functional ground for the internal shield. It should be green/yellow. The internal shielding and the insulation between the internal wiring and the accessible parts to which it is connected shall provide two safeguards, in which case they shall be interpreted in a random document. metal machine shop near me
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