A harmonic current compensator is connected in parallel with a harmonic generating load to a system power supply and supplies a compensation current Ia to limit a harmonic component contained in a load current IL to be input from the system power supply to the harmonic generating load. The harmonic current compensator includes: a load current detector that detects the load current IL; a compensation current detector that detects the supplied compensation current Ia; a control amount computing portion that computes a control amount of the compensation current Ia based on the harmonic component contained in the load current IL detected by the load current detector and the compensation current Ia detected by the compensation current detector; and a limiter that limits an upper limit of the compensation current Ia.

In a throttle device, a needle member (20) includes a tapered portion (20P) having a taper angle (2), and a length (X) along a center axis from a position (20PS) to an apical surface of the tapered portion (20P) is set to a value equal to or above a prescribed amount of lift (Lcos.sup.2 ), where the position (20PS) is a position corresponding to an edge (22as) of a valve port (22a) in a state where the tapered portion (20P) is inserted in the valve port (22a) and establishes a closed state of the valve port (22a).

Described is a regulation apparatus for a refrigeration plant having defined therein a refrigerant fluid path and a plurality of devices arranged along the refrigerant fluid path. The regulation apparatus includes a first sensor arranged in a first point (P1), and preferably a second sensor arranged in a second point (P3), both along the refrigerant fluid path. The control unit controls a first value measured by the first sensor and obtains a first regulation request of a device deriving from the first measured value as well as a second value measured by the second sensor, or calculated for the second point, and derives a second regulation request of the device deriving from the second measured value, compares the first and second regulation requests and establishes which regulation request is greater. A control unit commands an actuation device to actuate the most effective regulation request of the refrigeration plant devices.

An expansion valve includes: a body having a second passage through which a refrigerant returning from an evaporator passes, and a mounting hole communicating with the second passage; a power element mounted on the body in such a manner as to close the mounting hole; a shaft that transmits a drive force from the power element to a valve element; and a plate that separates an open space from the second passage, has an insertion hole, through which the shaft extends, coaxially along a central axis of the plate, and limits a flow of the refrigerant from the second passage into the open space to a flow through a clearance between the shaft and the insertion hole. The insertion hole is formed such that an opening area of the clearance between the shaft and the insertion hole is 7.0 mm.sup.2 or smaller.

A bulbless thermostatic expansion valve has enhanced joining of the power element to the valve body. The valve body includes an upper extension that extends from a main body portion, an end of the upper extension being crimped into a lip relative to an opposing surface of the main body portion thereby defining a recess that receives a portion of the housing of the power element to the join the power element to the valve body. The lip may be formed by roll forming the end of upper extension of the valve body. The housing of the power element may be a multipart housing including an upper housing and a lower housing, with a diaphragm being secured between the upper housing and the lower housing, and an end of the lower housing is the portion of the housing of the power element that is received within the recess.

In a throttle device, a needle member (20) includes a tapered portion (20P) having a taper angle (2), and a length (X) along a center axis from a position (20PS) to an apical surface of the tapered portion (20P) is set to a value equal to or above a prescribed amount of lift (Lcos.sup.2), where the position (20PS) is a position corresponding to an edge (22as) of a valve port (22a) in a state where the tapered portion (20P) is inserted in the valve port (22a) and establishes a closed state of the valve port (22a).

In a calculation process, a control unit calculates a feature quantity from a physical quantity obtained from a device within a predetermined period. In an estimation process, the control unit estimates the state of the device, based on the feature quantity calculated by the calculation process. In a restriction process, the control unit restricts the estimation process when an estimation restriction condition is satisfied, maintains restriction of the estimation process until a standby release condition is satisfied when a restriction release condition is satisfied, and releases the restriction of the estimation process after the standby release condition is satisfied. The estimation restriction condition is a condition in which there is a possibility of occurrence of erroneous estimation in the estimation process. The restriction release condition is a condition in which the erroneous estimation in the estimation process is suppressed.