Variable speed drive motors

Variable speed drive (motor, turbine, hydraulic). 

The high voltage variable speed drive motors. 

The screw-crammer system uses a conical hopper with a screw that is driven by a separate gear reducer and variable-speed drive motor. The output and effectiveness of the crammer are determined by the screw configuration and the available speed. The ram-type system, on the other hand, uses a pneumatic ram to stuff material into the screw. The ram is a piston-driven unit with the stroke timing adjustable by setting a series of timers located in the control panel. The feed section used by the ram system has an opening that is 12-14 times larger than that of a standard screw extruder. This allows low-bulk-density material to flow freely into the feed throat where the ram can compress it into the screw. Depending on the extruder size, the ram can compact materials with a force of 2000-9000 psi. 

A recirculation pump is to provide a constant mass flow to the reactor, regardless of the instantaneous fluid density. The pump is to be equipped with a variable-speed drive motor to maintain the desired mass flow rate throughout the start-up cycle. The pump is to be located in proximity to the heat exchanger within the shield building. 

V ri ble Frecjuency Drives. An important energy by-product of soHd-state electronics is the relatively low cost variable speed drive. These electronic devices adjust the frequency of current to control motor speed such that a pump can be controlled direcdy to deUver the right flow without the need for a control valve and its inherent pressure drop. Eigure 11 shows that at rated load the variable speed drive uses only about 70% as much power as a standard throttle control valve system, and at half load, it uses only about 25% as much power. 

In addition to energy conservation, the variable speed drives offer better control because of a faster response, ie, reduced dead band. They are also sometimes chosen for safety reasons because of elimination of the control station and accompanying valving. The capital saved by use of a smaller motor and elimination of the control valve partially compensates for the cost of the drive. 

Direct-Current Motor Control Control for dc motors runs the gamut from simple manual line starters to elaborate regulating systems. Only the starting problems are considered here since variable-speed drives and regulating systems are discussed elsewhere. 

Although motors and controllers can be bought separately, the trend is to purchase a system from a given manufacturer. There are six types oi variable-speed drives, as own in F ig. 29-73. Dynamic response indicates the ability of the drive to respond to a change in command it is measured in radians/second the higher the number, the faster the drive response. 

Another version of the dewatering screw that has been used successfully in a number of installations (Figure 40) consists of an inclined screw with a box-like back end and an internal overflow weir. The drive is usually a variable-speed motor reducer. Rotary air lock fitted with a variable-speed drive is typically used as shown in Figure 37 in connection with the plain receiving tank and an inclined screw conveyor. Materials of construction can be chrome-plated cast iron or nickel-hard casing. The rotary valve is made of hard faced tips or stainless steel replaceable blades. 

Figure 12-5F. Lubricated and nonlubricated balanced opposed process reciprocating compressors, designed to API 618 code. Fixed- and variable-speed drives using gas or diesel engines, steam or gas turbines, or electric motor. Note power drive to connect to right side of cross-head box in center. (Used by permission Bui. PROM 635/115/95-11. Nuovo Pignone S. P. A., Florence, Italy New York Los Angeles and Houston, Texas. All rights reserved.)...

Variable Speed Drive. This can be accomplished by turbines, direct current motors, variable-speed motors, or slip-ring motors. With the changing speed of the driver, the fan output capacity and pressure can be varied. For capacity reductions below 50%, an outlet damper is usually added to the system. 

Drive Types. Variable-speed drives may be selected on a chain-strength basis when operating with infrequent high chain loads such as from a torque convener, variable-speed motor, or multispeed transmission. 

Helical-lobe compressors are best suited for base-load applications where they can provide a constant volume and pressure of discharge gas. The only recommended method of volume control is the use of variable-speed motors. With variable-speed drives, capacity variations can be obtained with a proportionate reduction in speed. A 50 per cent speed reduction is the maximum permissible control range. 

Motor ) Changing to a variable speed drive (VSD). VSD s make startup easier and most can support 10% overspeed. 

Does increased agitator speed improve performance in the pilot plant If so, there is a potential scaleup problem. Installing a variable-speed drive with a somewhat over-sized motor can provide some scaleup insurance, the cost of which is apt to be minor compared with the cost of failure. 

Wiper blades attached to the moving distribution duct scrape the bottom and the sides of the tank and discharge settled sludge into the built-in sump, for periodic purging. The variable speed gear motor drives the rotating elements and the scoop. Electrical current for the gear motor feeds from a rotary contact mounted on the central shaft. 

Mobile phase is displaced from a chamber by using a variable speed stepper motor to turn a screw which drives a piston. The chamber has a volume of 200-500 cm3. The flow is pulseless, and can be varied by changing the motor speed. The mobile phase capacity is limited to the volume of the solvent chamber. Although this is fairly large, so that many chromatograms can be run before the chamber has to be refilled, a lot of solvent is wasted in flushing out the pump when a change is required. 

Agitator Turbine, 3.6 HP, 1750 rpm, XP rated motor, variable speed drive Circulating pump Viking series HL124, 2 HP, 1745 rpm, XP rated motor Micro Motion mass flow meter stainless steel 316L, 0-80 lb/min mass flow range, accuracy of 0.4% of range, XP rated with electronics unit mounted separately in nonhazardous area. 

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