Installation electric current sensors

Figure 6.69 gives an example for an optical current sensor. The light path is wound around a current-carrying conductor equidirectionally with the azimuthal magnetic field of the current. The rotation of the plane of the electric vector is not detectable on its own and is converted to light intensity variations by a polarizer/analyser combination. A photo diode is used as a light intensity detector. The optical sensor itself is installed in the - e - compartment, the electronics shall be protected in an adequate type of protection, e.g. in a small flameproof - d - enclosure or in encapsulation - m -. In the special case of an energy distribution system with combined - e - and - d - compartments, the optical fibres may enter the d-compartment to the electronics inside via bushings complying with d -standards EN 50018 or IEC 60079-1 respectively (Fig. 6.70). The evacuation of the sensors into the e-compart-ment results in additional available space in the more expensive d-compart-ment, compared with increased safety - e -. ...

Downstream of the converter, a DC bus connects this device in electric parallel with the battery pack to supply the electric drive. Voltage and current sensors are installed on batteries and upstream-downstream the DC-DC converter, as shown in Fig. 6.2, to monitor the electric energy flows between the different components of the propulsion system. The DC-DC converter allows the stack output power to be varied according to the selected control strategy. Furthermore, some security switches are adopted, in order to instantaneously disconnect the electric load from battery pack and/or stack. An I/O laboratory board is used for data acquisition and setting of the electrical parameter affecting the DC-DC converter behavior. 

When oil film breakdown has occured at the rolling surface during bearing operation, the ceramic balls are electrically Insulated. Therefore, electrical current flows only when oil film breakdown has occurred between the steel ball and the raceway surface. A magnet sensor is installed at the inner ring and retainer, and this is used to ascertain the circumferential angular position when oil film breakdown has occurred. 

Several measurements can be made after a coupon-type corrosion sensor has been attached to a cathodically protected pipeline. on potentials measured on the coupon are in principle more accurate than those measured on a buried pipe, if a suitable reference electrode is installed in close proximity to the coupon. The potentials recorded with a coupon sensor may still contain a significant IR drop error, but this error is lower than that of surface on potential measurements. Instant-OFF potentials can be measured conveniently by interrupting the coupon bond wire at a test post. Similarly, longer-term depolarization measurements can be performed on the coupon without depolarizing the entire buried structure. Measurement of current flow to or from the coupon and its direction can also be determined, for example, by using a shunt resistor in the bond wire. Importantly, it is also possible to determine corrosion rates from the coupon. Electrical resistance sensors provide an option for in situ corrosion rate measurements as an alternative to weight loss coupons. 

These inmitive concepts stand at the foundation of the electrical SHM methods for composite materials. This approach is deemed self-sensing because it relies entirely on measuring a material property (i.e., electrical characteristic) and does not require an additional transduction sensor the only instrumentation that needs to be installed on the composite structure consists of the electrodes. In the case of composite transport aircraft, the conductive screen skins currently used to mitigate lightning strike could potentially also serve as the measuring electrodes. Electrical SHM methods range from the simple measurement of the electrical resistance measurements up to more sophisticated methods such as electrical potential mapping, dielectric measurement, and electrochemical impedance. 

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