Inverter Connection

BobmanDad · 2 Nov 2013

I have a Union Graduate, 3 phase and an inverter. Should the inverter be connected directly to the motor?

The reason I ask is that the current setup has the motor, a control switch, a foot stop or brake thing and a lamp all connected to a distribution type box on the lathe.

The picture above shows the box just below the motor. On the right hand side the 3 brown wires with the number 5 on them are coming directly from the motor. On the left hand side the 3 wires coloured red, blue and yellow carry the incoming power from the 3 phase supply.

Presumably, if I connect the 3 brown wires from the motor to the inverter then I lose the on/off switch on the lathe, the lamp and the brake?

wizard · 2 Nov 2013

You must NOT use the switch

flh801978 · 2 Nov 2013

You always connect a VFD directly to the motor and use a new set of switches to the VFD's inputs and a 10k pot for speed control

wizard · 2 Nov 2013

Make sure the motor is wired at the same voltage as the inverter

CHJ · 2 Nov 2013

As per previous posters.

What type of invertor do you have?

Most 1ph to 3ph invertors need all three output wires continuously connected to the load (motor) for them to function correctly and avoid damaging the invertor.

The stop start NVR should be wired between the 1ph mains and the invertor input, any lighting or auxiliary wiring needs to be on the input side of the invertor.

wizard · 2 Nov 2013

also make sure the motor works ok before you wire the inverter to it or you may blow it up like i did

wizard · 2 Nov 2013

Most inverters are 240v in and 240v out and most motors are wired up at 400v and will need the wiring changing to 240v delta. When the motor is wired to delta to check it works ok wire it direct from your mains supply live to one wire neutral to the second wire and a second live through a capacitor to the third wire, spin the shaft and the motor should run. If it runs ok then it’s safe to use your inverter.