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I am not an electrician, electronics engineer or anything that will relate me with your interesting profession, but I am a Project Engineer, Mechanical Engineer, etc. and I am working in my spare time on one of my hobbies, so I would like to ask you guys kindly the following question:

I have an 220v electrical motor connected to an inverter which is fed with a 12v battery that I will use as a start up only, but once the motor reaches the max rpm, (the rpm must be controlled from 0 - 1500rpm) I want to replace(switch) the power supply from the inverter with a 220v permanent power supply ,let's say from the grid,but not necessarily.Is there any electronic, electrical or any device that could do the change of supply without interfering with the rest and in a faster way?

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    \$\begingroup\$ You can use a contactor which is effectively a very robust relay (or probably rather, two independent interlocked contactors) to switch single phase power from one supply to another. Keep in mind that depending on the size of the motor, the jump in phase may cause a large instantaneous torque on the motor and can damage it, so a circuit to sense the AC phases of both power supplies and properly timing changeovers may be necessary. \$\endgroup\$ – crasic Sep 3 '15 at 19:45
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    \$\begingroup\$ @crasic: Maybe post that as an answer. \$\endgroup\$ – Rev1.0 Sep 4 '15 at 19:09
  • \$\begingroup\$ If this is a series connected universal motor you could rectify the power going to the motor (after the switches to protect them) so that there will be no phasing issues. If you are slowly ramping up the inverter supply then at some point with a DC motor connection a pair of diodes could be used to allow the higher voltage source to drive the motor, switching in the mains when the battery supply is at full voltage could be automated if desired. \$\endgroup\$ – KalleMP Sep 4 '15 at 19:34
  • \$\begingroup\$ KalleMP, your answer makes more sense, I have seen in a video when this guy used a double switch he switched and I see the motor backdraft a little and re-established its own power keeping the generator working at his rated speed. \$\endgroup\$ – JOHN V Sep 8 '15 at 10:52

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