【正文】 to the area and are independent of load, guarantees the implementation of mechanism motion speed regulation and good stability。 and reduce the system stream pressure loss, improves the efficiency of the system. Load sensing control valve as the load sensing system core ponents, has many kinds of structure types. In Kato, Tadahino and Liebherr crane control valve load sensing system, employs a constant difference wins flow valve type, the priority valve type and its bination form.3 heavy machine limited stop protectionCrane motor control contactors are often dense onoff, therefore prone to breakdown. When the crane is in the process of operation required for accurate localization or emergency stop, because if the contact welding leads the crane refused to stop, there may be a collision accident. In order to solve this problem, propose a crane lifting mechanism refused to stop protection design.From three aspects to solve this problem, it is a contactor contact welding leads to the action logic, which can increase a middle relay to judge。 second is to avoid the contactor, relay petition leads to protection false start, therefore refused to stop protection setting short delay, which requires a time relay。 third is once contactor refused to jump, by the general circuit breaker shunt tripping action execution protection.From the perspective of crane electrical, prevent to stop are key measures to monitor whether the brake contactor contact welding. QRIS type lifting mechanism control cabinet adopts non stop protection circuit diagram design.The design of circuit is posed of three parts. The first is to monitor, made with brake contactor K07 coil is connected in parallel with the intermediate relay, K07 and K1 under normal circumstances is the synchronization action. If the K7 due to contact welding cannot release, so both movement is inconsistent, it will start delay time link.Second links, namely time delay is borrowed from the original design in the K03 time relay, consists of parallel K7 normally closed contact and a normally open contact of the control K07. K7, K07 parallel contact under normal conditions is always connected, stopping only when the K7 contact occurs when welding condition and connection to disconnect. K03 time relay is energized immediately attracted, poweroff time delay time delay release, , so long as the control circuit on electric, K03 immediately. And the main controller S40. At the start, stop switch process, even though the K7, K07 contact action of petition, instantaneous disconnection coil circuit, K03 time delay closing of the normally closed contact remained disconnected, so K7, K07 parallel contact access K03 coil loop does not influence the normal work of K03.In an access of parallel contacts before, only in the main controller to rise or fall 3 Block 2 block, due to acceleration level contactor K42 electric, K42 normally closed contacts open, K03 power release, the normally closed contact of the time delay closing, accelerating stage contactor K41 can attract, resection of third level dynamic resistance. In the master control down 2 blocks a block 0, a rise of 1 block when switching between the master controller, 17, 18 and 19, 20 contacts are disconnected, accelerating stage contactor K42 cannot attract, K03 may not power off, the normally closed contact also does not work, namely K03 in lifting mechanism for starting and stopping phase is actually not working. And refused to stop protection is working in crane stopping and starting stage, so can be used in K03 does not work all the time be borrowed for refusing to stop protection work, therefore, in the K03 loop of the coil is inserted in the parallel contacts. Once the K7 contact welding leads the crane refused to stop, parallel contact immediately disconnect, the K03 relay is deenergized, the normally closed contact of the delay after the closure, connect to the main circuit breaker Q0 shunt trip coil YA OFF, bringing the total tripping the circuit breaker, lift brake poweroff brake, achieve the purpose of non stop protection.The third link is non stop protection starting point, which consists of a K03 time delay closing of the normally closed contact of the normally open contact, K7, K07 normally closed contact with the total circuit breaker shunt trip coil connected in series. Main breaker just closing moment, K07 normally closed contact has not yet been disconnected, so we must in the series circuit access K7 normally open contact, otherwise it will cause shunt trip coil gets electricity, making the total circuit breaker tripping just closing immediately. K07 normally closed contact role is to prevent the K03 in the execution of the original design features, . delayed resection third starting resistance, resulting in a total circuit breaker tripping. Because of the crane is accelerated stage, K07 normally closed contact is disconnected, so the shunt trip coil K03 will normally closed contacts closed and electricity, resulting in incorrect trip.If the crane braking contactor before starting K7 contact is welded, so a total circuit breaker Q0 because the shunt contact is opened, so that the K03 is in an off state, K03 normally closed contacts closed, normally open contact, while the K7 K07 normallyclosed contacts are closed, so the shunt trip coil gets electricity, so just close general circuit breaker tripping prevent crane in immediately, not braking condition start, eliminate accident hidden danger.For the maintenance of safety, the original design of lifting mechanism control power conversion switch Q3 by diode instead of quadrupole, so Q3 disconnected, cut off the lifting control circuit and circuit breaker shunt tripping circuit connection, ensure the lifting control circuit power. Q3 can use HZ5 10 type quadrupole bined switch.By the use of the original design of the time relay, crane lifting mechanism of non stop protection only needs to add an intermediate rela