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	Subject - Electric Motor Selection Jacob What are the parameters, which decide optimum value of motor operating voltage (ie terminal voltage ) among the choices such as 3 phase 400V, 3.3 kV, 6.6kV, 11kV etc. ? (This particular application involves motors for pumping stations) JimmyDee A voltage for a motor is decided on several factors. First is cost. Up to about 200 HP, a standard 480 volt 3 phase motor is going to be the most cost effective. Wire feeding the motor will not be excessive on cost. As the motors get larger from there the amps will increase to a point that the amount of copper will be cost prohibitive. Both in the feed and motor. Size of motor will increase in size. 4160 is the next most popular voltage. Copper size is much smaller and I seen HP ratings up to 1200 HP but I'm sure they go larger. 7200 and 13,200 are for the big boys. I've seen a 2500 HP that was 13,200 volts and the size of the copper was very small for this size motor. The largest single phase motor I've seen is a 5HP. They are started with a capacitor and are 3-4 times the money compared to a 3 phase motor. I think they will go by the way side because 3 phase motors can now be run on single phase with a phase converter or Variable Frequency Drive. Jim Scott Vickrey Well said Jim. In order to determine voltage. You need to know what motor(s) you will be using. The motor(s) will state their required voltages. In other words first you need to find the optimum motor to get the optimum voltage. So, get with a motor salesperson and have them help you decide which is the best motor(s) for the pump(s). Then you will know what voltage you'll need. Jim, The largest motor I've seen in person was a 2 speed 4000hp used to drive a very large polyethelene plastic extruder. This thing was a beast and when you kicked it into high gear it would scream and brown out most of the HID lighting . It used 13.2kv I have also wired a 10 hp single phase motor, it was old and used to drive a pecan classifier. The motor housing was about the same size as a 25 hp three phase motor.