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My new VFD
- Thread starter martik777
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I have been known to be wrong, but I would have to say a form no!. The reasonoing is they are big at warning you that no voltages should be applied to the output terminals, and failure to heed that warning, can cause bad things. I would think that running two in parallel, will do the same bad things. it would be impossible to be sure the two outputs are exactly the same. if they are not exactly the same, one will be putting power in the output terminals of the other.
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They could also possibly be out of phase from each other.
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No because there is no way to separate the outputs and therefore no way to prevent overloading of the individual units
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I guess it might help to know what your needs are. If you are intending on powering a multi motor machine, its best to have one VFD per motor. I've been told conflicting info, and ways taht I could power the fractional HP coolant pump motors on my mill, and drill press, with the same VFD as one of the motors, but plan on just getting them each their own VFD eventually.
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My main concern is my Gorton mill, which is 10hp on the spindle, 3hp on the X,Y, and Z axis, plus the coolant pump. So it looking like maybe a 10hp and a 5hp inverter would do it. My big lathe is 7.5 hp so I can use the other 10hp inverter there. Thanks for the input. Mike
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Typically VFD's need to be directly connected to the motor and it is a 1:1 pairing for the motor specifications and overload characteristics. There are cases where a VFD can be paired to multiple smaller motors of the same specifications, but each motor needs a separate overload device. The VFD cannot be used in a sensorless vector mode only a V/Hz setting. Using contactors and switches between the VFD and motor(s) may destroy the drives. The other issue is that although the stated Hp/kW rating on these VFDs may state 10Hp, the internal components and design is more for high speed spindle motors with very little load. So it may or may not work trying to start something like a lathe that doesn't have a clutch. Trying to run something like a 10 Hp compressor with one of these 10 Hp VFD's usually ends up with smoke coming out of the unit.
I would start with trying the 10 Hp on the mill main drive motor. Use one 5Hp VFD for the drives, the coolant pump would need a separate VFD or try to switch to a single phase pump system. Also check that all the drive motors are AC 3 phase, typically these drives are DC for the variable speed and you cannot use a VFD to power these. On some of the smaller Groton they are the Dyna-Drive they are powered by 115V via a transformer which connects to 2 legs of the 3 phase power.
I would start with trying the 10 Hp on the mill main drive motor. Use one 5Hp VFD for the drives, the coolant pump would need a separate VFD or try to switch to a single phase pump system. Also check that all the drive motors are AC 3 phase, typically these drives are DC for the variable speed and you cannot use a VFD to power these. On some of the smaller Groton they are the Dyna-Drive they are powered by 115V via a transformer which connects to 2 legs of the 3 phase power.