Understanding Three phase motors with multi speed

[SIPHON]

Hi guys,
I am wondered if anyone had any good links or basic advice on understanding High and low speed on 3 phase motors (415v) with 6 terminal connections.Usually used in large air conditioning supply fan units? Usually the main A/C plant has a selector switch for low or high speed. Nowadays new plants come fitted with vari-drives which takes away all the hard work. I ve tried searching online but very limited and haven't found much that explains it very well.


How would you wire up the motor so it does low and high speed ?
How are the windings configured so that the motor operates in 2 speeds.
Basic wiring diagram will help.
Regards
siphon :)

[Sandro Baptista]

One of the options is the Dahlander motor. Look it at the internet.

[chillin out]

Here is a link to some information...
http://tinyurl.com/3ap5ma4

I always thought the speeds were the same, you need a motor with 9 wires to get speed control, here is a link to use tapped windings...
http://tinyurl.com/449smsg

Chillin:):)

[goshen]

Hi SIPHON
try these links http://www.mandc.co.za/pdfs/Star_Delta_Starting_and_Dual_Voltage_Motors_Explained.pdf (http://www.mandc.co.za/pdfs/Star_Delta_Starting_and_Dual_Voltage_Motors_Explained.pdf)
http://www.servorecambios.com/ABB/diagrconex.pdf
http://www.danfoss.com/NR/rdonlyres/B7FA9B72-37CF-4C91-9101-CFF774CF78BB/0/K06Motors.pdf

as you said, today most motors are speed controlled via VSD that is both frequency & voltage control,
" way "back we use to change speeds via a dahlander connection as mentioned above or by any other varyation of wiring inside the motor,thus changing only the voltage.

i am sure you are aware of the advantages of using VSD'S rather than any other method of speed control .

good luck

[Sandro Baptista]

Hi SIPHON
try these links http://www.mandc.co.za/pdfs/Star_Delta_Starting_and_Dual_Voltage_Motors_Explained.pdf (http://www.mandc.co.za/pdfs/Star_Delta_Starting_and_Dual_Voltage_Motors_Explained.pdf)
http://www.servorecambios.com/ABB/diagrconex.pdf
http://www.danfoss.com/NR/rdonlyres/B7FA9B72-37CF-4C91-9101-CFF774CF78BB/0/K06Motors.pdf

as you said, today most motors are speed controlled via VSD that is both frequency & voltage control,
" way "back we use to change speeds via a dahlander connection as mentioned above or by any other varyation of wiring inside the motor,thus changing only the voltage.

i am sure you are aware of the advantages of using VSD'S rather than any other method of speed control .

good luck

On Dahlander motors you change rpms by changing the number of poles of the motor.

[goshen]

Hi sandro
yes you are correct ,but by changing poles, you are still limited to very certain speeds 1400-2900-etc....
using a VSD, lets you basicly change to any speed wanted, pending motor manufacturer approval.

[Peter_1]

Goshen, I clicked further to one of the links you gave...http://www.qtime.co.za/CV_Published_Papers.html and this man wrote good papers. Thanks Goshen.

[SIPHON]

Thank you for all the informative links very useful and very simplified.

[Sandro Baptista]

Hi sandro
yes you are correct ,but by changing poles, you are still limited to very certain speeds 1400-2900-etc....
using a VSD, lets you basicly change to any speed wanted, pending motor manufacturer approval.


You're right. I'm not against the VSD. I also like to use it.

[goshen]

HI all
happy to be of help !

[Mick13]

i think maybe hes referring to delta and star setups?
maybe im wrong? but with a 3 phase motor (6 terminal connections) wired in star it will run slower and draw less current (low speed) and when wired in delta it will run faster and draw more current (high speed).

[Sandro Baptista]

i think maybe hes referring to delta and star setups?
maybe im wrong? but with a 3 phase motor (6 terminal connections) wired in star it will run slower and draw less current (low speed) and when wired in delta it will run faster and draw more current (high speed).

If the machine is a compressor working with aprox. constant Torque (not a fan) if you used star the motor could be thermal over loaded.

[SIPHON]

This is a large air conditioning supply fan with a selection switch for low and high speed