bridgeport 2 speed motor and VFD

[julien cirketParticipant @juliencirket51522]

hi saw some threads long time ago about using a VFD on a bridgeport mill i have a jhead with a 2 speed i think pancake motor , have rewired the rest of the mill ie lights and cross feed to run on 110 v so all works fine, but am now stuck for the motor i have purchased the VFD but i did hear that the motor has to be rewired and now im stuck i have 3 blue and 3 yellow wires coming out of the motor , i am a very much bit of a novice with wiring so if some one has any advice or help it will be greatly appreciated

[julien cirketParticipant @juliencirket51522]

help

[Chris Evans 6Participant @chrisevans6]

My Bridgeport has the single speed 2HP motor and varidrive, runs well on a Chinese VFD.

I was told that VFDs are difficult to wire for a two speed motor so I hope to learn something from this thread for future reference.

[John BaronParticipant @johnbaron31275]

There should be a rating plate on the motor giving 440/220 volt and star/delta connections. It needs to be wired in delta to run on 220 volts, from a VFD.

[Clive FosterParticipant @clivefoster55965]

The common Dahlander connection two speed motors cannot be run off an ordinary 220 V output VFD because they don't have alternative low voltage (220 V) Delta and high voltage (440 V) Y connection capability. They require 440 V input for both speeds with the coils laid out Delta style for low and Y steel for high.

There are six windings in the motor. For low speeds the windings are connected in a series loop with power applied to every other connection. So 440 volts is applied across each pair and the individual windings see 220 volts each. For high speed the windings are connected in parallel pairs. One end of each pair goes to a common point the other end receives power. So each winding sees 220 volts.

You can run a Dahlander motor in high speed setting off a 220 V VFD by connecting the windings in parallel pairs and running them in a series loop with power applied to each corner. Effectively each parallel pair is equivalent to the single windings on a normal three phase motor in Delta connection. Not something for the novice to try. Its very, very easy to get things muddled up with paired windings out of phase or not correctly paired. Not something I'd try. I could do it but wouldn't if you see what I mean.

Wikipedia has an adequate, albeit small, diagram of the coil layouts :- **LINK** . Google search will show up plenty more pictures but most aren't linkable. This is quite a good one showing the switching involved :- **LINK** for speed changing.

Clive

Edited By Clive Foster on 01/09/2018 17:18:01

[Author]

Posts