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ALTERNATING or LOAD SHARING relays are used where two or three electric motors share the workload. This is often the case in pump and compressor applications. Let's take an example where two pumps are being used to fill a tank. One pump is all that is really needed, but this is a critical tank in the chain of the process. If this tank ever ran dry, the entire assembly line would shut down. So, a second pump is installed in case the first one fails. If the standby pump isn't used for several years, it might fail to start when called upon to relieve the first. This is where a M3FFR should be used. It is fitted with two outputs. Each time the level controller calls for a pump, the M3FFR gives the signal to the pump that was last idle via its magnetic starter. This way, each pump operates on an alternating basis. There's another feature on this alternator which is most useful. We call it the help function. This allows a second input to be connected which calls the idle pump into action so that both operate in order to meet the demand. In our example, a second level control can be set as the low-low level indicator. This type of arrangement can even help to reduce the size of each pump. The M3LS3 is for applications where three motors are being controlled. |
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