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Printing Equipment in the protection of induction motors


Fault, and issued the corresponding action command. It features simple structure, using SCM to complete, for industrial control. 2. Temperature sensing type of protection device (1) bimetallic temperature relay it directly buried people in the motor windings. When the motor overload to make the winding temperature rises to near the limit, the double contact with a heated metal to bend, break and cut off the circuit to make contact products such as JW2 temperature relay. (2) thermal protector is mounted on the body to use the motor thermal overload relays acting. The difference is that with the temperature relay with 2 contacts the bowl touch the bridge as a double metal strings in the motor circuit, both overload current flows through its heat, but also the motor temperature to heat up, reaches a certain value, moment of rebound double-metal action, contact off, breaking the motor current. It can be used for small three-phase motor temperature, overload and phase failure protection. Products such as sPBDRB thermal protector. (3) detection coil temperature of motor stator windings of each phase coil embedded test 1-2, the self-balancing thermometer to monitor the winding temperature. (4) thermistor relay is directly embedded in the motor windings, once exceeding the prescribed temperature, its resistance increases rapidly 10-1000 times. When used, together with the electronic circuit testing, then the relay. JW9 series of marine electronic products, such as temperature relay. Protective device coordination with the induction motor in order to ensure the normal operation of induction motor and its effective protection, and protection must be considered asynchronous motor coordination between the devices. Especially the big 64 China Packaging 2008 / 5 the capacity to use small-capacity power induction motor, the protection coordination is more prominent. 1. Overload protection devices and motor coordination (1) overload protection action time should be slightly longer than the motor starting time point. Motor overload protection features only to escape motor starting currents in order to ensure its normal operation; but its action time not too long, and its properties can only be played under the thermal characteristics of motor overload protection function. (2) the instantaneous current overload protection device should be higher than the impact of motor starting current is slightly larger. If the overload protection device with a transient motor function, its action current action current than the peak should be larger in order to properly start the motor. (3) overload protection action time should be smaller than the thermal characteristics of conductors, in order to play back-up power supply line protection. 2. Overload protection device and short circuit protective device coordination does not have a general protective device short-circuit current breaking capacity. Once the short-circuit in operation,[link widoczny dla zalogowanych], need for the series in the main circuit in short circuit protection device (such as circuit breakers or fuses, etc.) to cut off the circuit. If the fault current is small,[link widoczny dla zalogowanych], belong to the overload range, is still cut off by the overload protection circuit. So between the two movements should be selective. Fuse short circuit protective device characteristics are described as representatives, the intersection curve with the overload current Ij, if the fuse into account the dispersion characteristics, the intersection of the two currents Is and IB, this time Is on the requirements and the following Over-current overload protection device to cut off the circuit should be,[link widoczny dla zalogowanych], Ib and above the limit until the permitted short-circuit current U by the short-circuit protection device to cut off the circuit to meet the selective requirements. Clearly, in the context of Is-IB is difficult to ensure that there is selectivity. Therefore requested that the scope should be as small as possible. IEC standards from the current point of view, limit the Is = O. 751j, Ib = 1.25IJ. Current overload protection device rated making and breaking capacity according to 0.75IJ assessment, which is substantially lower some standards from the IEC to modify the movements of a possible future examination by IJ in order to improve its reliability. Therefore,[link widoczny dla zalogowanych], the coordination of the above should take into account both their selectivity, but also to consider making and breaking its rated capacity. Motor protection is related to electrical installations and mechanical equipment reliability, the normal operation of one of the keys. Direct detection of the temperature of the motor windings to protect the overload caused by overheating is a very effective protection, but because of the motor windings to be embedded directly in the more expensive, maintenance difficulties and other reasons, often operating only in some occasions; from the economic considerations , using current detection type is more advantageous to heat the relay is still a cheap, simple, reliable motor protection form (from the actual situation,[link widoczny dla zalogowanych], the current account for the majority.) High performance requirements of the action and the functional requirements of the whole or expensive high-capacity motor protection, you can use electronic or solid state relay; on the general requirements, is applied with thermal magnetic tripping a circuit breaker motor protection more practical . But no matter what kind of protection device used must be considered and motor overload protection device, overload protection devices and short circuit protective device coordination.

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