Thread: Delta or Star

Is there a way to check (test) if a 3 phase motor is wired in Delta or Star.

Are you able to access the terminal block on/in the motor at all? If so, there should be 6 terminals (usually two rows of 3). If it's in star configuration, three of the terminals will be hooked together (a star point). If it's in delta, each one of the terminals will be hooked up to the next one across in the parallel row.

Star
._._.
. . . < Input wires

Delta
. . . < Input wires
././. < This end one will loop around to the first one in the top row.

I hope that makes sense.
Steve

This might help

IMG_3530.jpg

This is Y as there are metal strips connecting W2m U2 and V2
IMG_3531.jpg

If you are not sure post a picture of your open connection box.

This is what I have on the motor, it is about 50 - 60 years old off a Denbigh Mill.

DSC03982.jpgDSC03983.jpg

G'day Shane,
The Triangle Stamp a couple of squares over from the voltage rating on the spec plate suggests to me that you have a 400/430V Delta connected motor.
The wiring inside the terminal panel looks to be delta connected.
Unfortunately this is not ideal if you plan to run it from 240V 1~ with a VFD.
Cheers,
Greg.

`It is Delta. It has the Delta sign on the plate. Pretty much expect that for an old UK made three phase motor.

I thought it had to be Delta to use a VFD.

See the triangle symbol, to the right of the " V 400/440 " ?
That means Delta.
a.

No, it is all to do with the voltage the motor will run at.

If a 415V electric motor is wired in wye, you can rewire it to Delta and you can run it on 240V three phase.

If a 415V is wired Delta, if it was wired to Wye, I guess then the correct voltage would be something large.

Originally Posted by Auskart

I thought it had to be Delta to use a VFD.

You can run that on a VFD

BUT

1) to get full power you will have to run it on a VFD that has a 415V input and a 415V output

2) You can also run it on a VFD that has 240v single phase input - 240V 3P output, but it will only run at half power.


As RC says, what you want is either
a motor that is already 240V Delta
OR
a motor that is a 415V "Star" or Y connected, which can usually easily be rejigged to delta - then running this on 240V will give full power.

Hi Shane,
A VFD will work on either star or delta connected motors.
When a motor is connected in star, there are two windings connected in series between each phase.
When a motor is connected in delta there is only one winding connected between each phase.
A star connected motor requires a higher voltage to generate the same field as delta connected motor as it has twice the impedance (not technically correct but good enough for this discussion).

A lot of 3~ motors found on workshop machinery have a specified voltage of 415 (or somewhere thereabouts), are hard star connected and designed to run on 415v (between phases) to achieve their rated power. Sometimes the spec plate will indicate that the motor is star connected but not always, I think it's a bit of a given that if the plate specifies 415V only with no indication of how the windings are configured then it's star connected. These are electrically and mechanically the same as the next type of motor but not designed to have the winding connections changed by the end user. These are the ones that people dig into the windings so they can convert them to delta.

Some 3~ motors have a spec plate listing a required voltage of 240/415 (or thereabouts) this is a good indication that it can be configured by the user to either delta or star and require 240V between phases if delta and 415V if star to achieve their rated power. Basically the same as the first type just more user friendly.

Some 3~ motors (like yours) have a spec plate listing a required voltage of 415v (or thereabouts) and indicate that the motor is delta connected. These have different windings to the first two types (more turns in each winding) and require 415V between phases to achieve their rated power.

While some VFD's can convert 1~ to 3~ the voltage between phases will still only be 240V.
If you have either of the first two types of motor and manage to connect the windings in delta the 1~ to 3~ VFD will run it and achieve the rated power, happy days.
If you have either of the first two types of motor and connect them in star the 1~ to 3~ VFD will still run it but the output power is derated by at least 50%, not so happy days but you can fix it.
If you have the third type, the 1~ to 3~ VFD will still run it but the output power is derated by at least 50%, not so happy days and nothing you can do about it unfortunately.

Hope this helps clear things up a bit.
Cheers,
Greg.

Originally Posted by kwijibo99

Hi Shane,
A VFD will work on either star or delta connected motors.
When a motor is connected in star, there are two windings connected in series between each phase.
When a motor is connected in delta there is only one winding connected between each phase.
A star connected motor requires a higher voltage to generate the same field as delta connected motor as it has twice the impedance (not technically correct but good enough for this discussion).

A lot of 3~ motors found on workshop machinery have a specified voltage of 415 (or somewhere thereabouts), are hard star connected and designed to run on 415v (between phases) to achieve their rated power. Sometimes the spec plate will indicate that the motor is star connected but not always, I think it's a bit of a given that if the plate specifies 415V only with no indication of how the windings are configured then it's star connected. These are electrically and mechanically the same as the next type of motor but not designed to have the winding connections changed by the end user. These are the ones that people dig into the windings so they can convert them to delta.

Some 3~ motors have a spec plate listing a required voltage of 240/415 (or thereabouts) this is a good indication that it can be configured by the user to either delta or star and require 240V between phases if delta and 415V if star to achieve their rated power. Basically the same as the first type just more user friendly.

Some 3~ motors (like yours) have a spec plate listing a required voltage of 415v (or thereabouts) and indicate that the motor is delta connected. These have different windings to the first two types (more turns in each winding) and require 415V between phases to achieve their rated power.

While some VFD's can convert 1~ to 3~ the voltage between phases will still only be 240V.
If you have either of the first two types of motor and manage to connect the windings in delta the 1~ to 3~ VFD will run it and achieve the rated power, happy days.
If you have either of the first two types of motor and connect them in star the 1~ to 3~ VFD will still run it but the output power is derated by at least 50%, not so happy days but you can fix it.
If you have the third type, the 1~ to 3~ VFD will still run it but the output power is derated by at least 50%, not so happy days and nothing you can do about it unfortunately.

Hope this helps clear things up a bit.
Cheers,
Greg.

Thanks Greg, so if I was to connect this motor to a VFD it would give me 1.5 Hp instead of 3 hp and would it change the speed of the motor as well.

Thanks Shane

Originally Posted by Auskart

Thanks Greg, so if I was to connect this motor to a VFD it would give me 1.5 Hp instead of 3 hp and would it change the speed of the motor as well.

Thanks Shane

The frequency controls the speed of the motor and is adjustable with a VFD.
So at 50 hz it would still spin at 1410 rpm, or there abouts