delta star motor connection 2

[caribou]

Is there an advatage to running a motor in delta configuration if it starts and runs without a problem in star configuration.
Steady state and statup current are both less in the star configuration, indicating higher efficiency. Less electrial stress on armature in star as well.

 

[Marke]

Hello caribou

There are a nuimber of posts about this question on this forum, but to summarize, effectively, when you connect a motor in star, you increase it's voltage rating by rt3, or if you remain at the rated delta voltage, you reduce the effective motor rating to one third. If you are able to guarantee that the motor will never exceed one third of its delta rating, then you can leave it connected in star, otherwise, you will operate at excessive slip and cause the rotor to fail.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[jbartos]

Suggestion to caribou (Electrical) Dec 12, 2003 marked ///\\Is there an advatage to running a motor in delta configuration if it starts and runs without a problem in star configuration.
///If the motor manufacturer designs the motor for delta connection continuous duty and not wye connection continuous duty or preferred duty, the motor should be run at that connection.\\Steady state and statup current are both less in the star configuration, indicating higher efficiency.
///Check the motor efficiency curve for load 1/3 or less of delta connection via manufacturer provided motor efficiency versus motor load curve.\\ Less electrial stress on armature in star as well.
///Yes, if the shaft load is reasonable for this connection.\\\

 

[skeandhu]

Why are some motors connected in star as opposed to Delta or vice versa?
1/Star connection is used mainly on small motors up to 20KW.
2/Connection in Star increases the Start and Run currents of all 3PH squirrel cage induction motors.
3/Remember Phase voltage = Line V divided by Root 3
4/So this increases starting current
5/This higher starting current gives increased torque.
6/This is important in smaller motors as they due to their size {less copper} do not have the same inductive power as larger motors connected in Delta.

 

[GusD]

Hello caribou


The factors taken in consideration when choosing between a Wye and Delta is the number of available paths for the pole count and the number of turns per coil required for a design. This would determine the number and size of conductors used in the coil.
Generally the smaller motors use a one path Wye connection and the larger motors use the maximum number of paths with a delta connection. This is to keep the number of turns and parallel conductors reasonable for manufacturing.
On motors designed for Wye or Delta operation (6 leads) you could run it as you wish as long as the volts/turn remains the same.Efficiency should not vary if operated within its limits.

Take care



GusD