摘要:
A solenoid operated hydraulic control valve system including a solenoid operated valve having a specially ported spool valve to statically balance spool forces in the opened and closed positions.
摘要:
An improved electrically actuated solenoid is used to regulate the function of a hydraulic flow control valve. The solenoid directs a control valve to generate a predetermined output pressure as a function of the solenoid input current. The working air gap surface area is increased by locating it at a greater circumferential radius than the pole piece to increase the air gap permeance, thereby increasing the output force obtainable from a solenoid of relatively small physical dimensions and low cost.
摘要:
A solid state circuit interruption arrangement monitors a current path to provide protection to both a load and a solid state switch. The arrangement includes an energy absorber for absorbing energy from the current path in response to the solid state switch interrupting the current path, and a control circuit for periodically generating the interrupt signal to interrupt the current path for prescribed intervals and to control the current supplied to the load between a maximum current level and a minimum current level.
摘要:
A solenoid operated hydraulic control valve which has a specially ported spool valve to statically balance spool force in the opened and closed positions, and a specially designed solenoid operator which includes very small ratios of gaps to cross-sectional areas for the working and non-working gaps between the armature and stator.
摘要:
A static switch including main and auxiliary SCR's has a commutating capacitor coupled between the common connections of these main and auxiliary SCR's. An independent external charging circuit is provided and connected to complete a charging path for the commutating capacitor which is isolated by at least one diode from the main d-c bus. This enables the commutating capacitor to charge to a level above that of the d-c bus voltage and maintain effective commutation.
摘要:
A solid state circuit interruption arrangement in a distributed power network provides fast and reliable circuit interruption. A common power source provides power to a plurality of loads via respective current paths. A main circuit breaker and a plurality of solid state circuit breakers are arranged to interrupt the current paths in response to command signals sent from a central controller. Current sensors and voltage sensors are coupled to the current paths for monitoring purposes. An automatic controller responds to any of the current sensors detecting a fault condition by automatically generating a command signal, which forces the associated solid state breaker to interrupt the associated current path. Thereafter, the controller automatically generates a signal to the main circuit breaker to interrupt the power provided from the common power source in the event that the associated current path is not interrupted by the solid state breaker. Alternatively, or in addition, the main interruption device may interrupt the current path when its own internal sensing mechanism detects a magnitude of current that is beyond a predetermined level. Also, the controller automatically generates a signal to the main breaker to interrupt the power provided from the common power source in the event that any of the branch breakers fails in the "off" or interrupted, condition. Other features include a finned housing structure which provides cooling means for the breaker system without the need for cooling fans.
摘要:
A method and apparatus for solenoid driver control of high speed solenoid actuators which includes supplying a high regulated level of acceleration current to operate the actuator, monitoring and controlling the current requirements of solenoid actuation, automatically reducing the solenoid current at a rapid rate to a lesser level of regulated solenoid hold current for the remaining duration of actuator operation, and rapidly reducing the solenoid current between acceleration and holding levels and for rapid solenoid release. Current is controlled at the different levels using switch mode power control techniques for power efficiency.
摘要:
Stabilized operation of a damperless synchronous motor, which is driven by a voltage source inverter energized by a d-c bus voltage, is obtained under transient conditions, such as during sudden variations of load torque, in order to maintain the torque angle in the motor relatively stable at all times and within the stability limit. This is achieved by employing transient changes in either the d-c bus voltage, the d-c bus current or the motor voltage, which changes reflect transient variations of the torque angle, to rapidly adjust the inverter frequency as necessary to hold the torque angle reasonably constant. For example, if there is an abrupt load increase on the motor, the bus voltage tends to drop and the motor tends to slow down, the torque angle thereby tending to increase. The extent to which the angle tends to increase will, however, be rapidly reduced by dynamically decreasing the inverter frequency so that the rotating magnetic flux or mmf, produced by the stator windings of the motor, slows down to preserve the desired torque angle. When there is a normal variation in load demand, necessitating a different steady state motor speed, a set point voltage may be varied to change the amplitude and frequency of the inverter output voltage to the steady state levels needed to drive the motor at the new required speed.
摘要:
A relatively simple inverter-motor system, comprising a minimum number of circuit components, is provided by employing a voltage-controlled thyristor inverter which in turn drives a synchronous motor having a leading power factor. With the motor current leading the motor voltage, the thyristor switching devices will be motor-commutated, thereby precluding the need for any auxiliary commutating elements or circuits to effect forced commutation. Since, with a leading power factor, the current through a conducting thyristor falls to zero before the thyristor has to be switched off, ample turn-off time is provided. Furthermore, as compared to a conventional forced commutated voltage source inverter, the customary reactive diodes, usually shunting the switching devices in an inverter to permit the flow of reactive motor current, are not necessary. Moreover, by powering the inverter with a voltage source, rather than with a current source, the commutation process is greatly facilitated, the need for damper windings on the motor is eliminated, and the physical size of the d-c link inductor normally required by a current source inverter is greatly reduced.
摘要:
If the thyristor switching devices of a chopper controlled inverter are normally motor-commutated during running operation, a starting system is needed to initially rotate the motor fast enough to develop a sufficient back EMF in the motor for motor commutation to occur. This is achieved by regulating the operation of the chopper to produce bus current pulses and by gating the thyristors on in predetermined sets and in a prescribed sequence to current pulse energize the motor to effect step-by-step rotation. After a set of conducting thryistors have supplied a bus current pulse to the motor, the reactive energy that builds up and becomes locked or stored in the inductances, through which the motor current flows, must be dissipated in order to commutate the conducting thyristors off and reduce the motor current to zero before the next set of thyristors are turned on. The required energy dissipation is accomplished by a circuit path which is effective during the intervals between the bus current pulses from the chopper. A d-c voltage source, in the circuit path causes the reactive energy to be rapidly absorbed, to permit faster turn on of the next set of thyristors and consequently faster starting. Once the motor has reached a speed sufficiently high to permit motor commutation to occur, and SCR is gated on to by-pass the d-c voltage source and provide a low loss free-wheeling path for reactive energy during running operation of the system.