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Variable Speed Pumps Try to Work Like Cycle Stop Valves Some companies are promoting variable speed pumps. We stopped using variable speed pumps in 1992. There is no energy savings using these variable speed pumps when maintaining a constant pressure. Variable speed pumps do not have a pressure bandwidth to work with. This makes a pressure tank unable to deliver any draw down. These pumps must come on every time someone has an ice maker fill or a tooth brush is washed. The many problems we had with variable speed pumps and large pressure tanks are what got us to using constant pressure valves. In the twelve years we have been supplying constant pressure valves we have not pursued approval for municipal use because of all the tank regulations. There are millions of other uses for our valve other than municipal. States are now being ask for approval of our valve by local pump installers and end users. These pump installers and end users realize that the nursery, dairy, irrigation and other systems that have used Cycle Stop Valves are costing less to install and to operate than when using other types of pump control. Many of these people do not understand why the flowers and cattle should have pump systems that deliver better pressure and cost less to operate than those used for human consumption. Variable speed drives vary the speed of the motor which reduces the flow from the pump. These drives may try to accomplish the same objective as a Cycle Stop Valve but, have a multitude of problems. Slow reaction speeds programmed into the drive can accentuate the surge in pressure. When more flow is demanded, if there is any delay in response time by the drive, pressure will dip low before the drive catches up. When less flow is demanded pressure can surge dramatically during the time it takes for the drive to slow down the motor . These delayed response times cause swings in pressure that can be devastating to piping systems. Secondly every component in a pump or motor has a mechanical frequency. Each time the pump passes through or operates at that particular speed or frequency, that particular component creates harmonic vibration causing damage. Another problem with a drive or inverter as it is sometimes called is that it sends a pulsing DC voltage to the motor. This pulsing DC voltage is responsible for transient voltage spikes which can be many times the operating voltage of the motor. Pulsing DC voltage also has an accumulative effect in motor leads. The longer the motor lead, the higher the voltage of the transient spikes received by the motor. Obvious proof of these spikes exist in that many new or rebuilt motors are being labeled with tags reading "VOLTAGE SPIKE RESISTANT WINDING, SUITABLE FOR INVERTER DUTY". Other problems with drives include a lose of motor efficiency, carrier wave distortion, EDM currents in the rotor, heat dissipation, power fluctuation intolerance, and a high purchase cost. Drives are microprocessor based, making repair parts obsolete as new computer chips replace the ones that are only a year or two old. Last of all when the drive does malfunction, an expert must usually be flown to location for repairs, at considerable expense. Cycle Stop Valves benefit pumps and motors. Operating at a constant speed eliminates vibration problems. Across the line or soft start panels operate the motor with standard AC voltage, which has a smooth sinusoidal wave, eliminating voltage spikes. Without a drive, all other drive related problems are never present. Throttling a constant speed pump with a valve can also reduce power consumption close too or as much as slowing the motor with a drive. Simply working a full speed pump further left on its curve is not only good for a pump but, can save enough energy, to make it impossible to ever payback the added expense of using a drive. |
| Cycle Stop Valves® is a registered trademark. All right reserved unless prior authorization is obtained. Cycle Stop Valves are patented: Patent number 5,988,984 and other patents pending. |
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