Star delta

[Adel abdulhammed]

Hello everyone
I'm New in the form yesterday I found electric panel is looking strenge. inside panel vsd and Star Delta control circuit for water pump motor
Why we use both together
Why we use both?
I think one method is enough

 

[Ethnan]

Star connection is better for low loads. If your pump is below 5KW, then you have lower current in each line, and low starting torque required.
A star connection will draw less current at start than a delta connection, and because this is a solar panel, your power is limited, so go star connection.

 

[waross]

A star connection will draw less current at start than a delta connection

Starting current is somewhat moot with a VFD.
I suspect that a VFD was installed and that the original star-delta starter was abandoned in place.
On the other hand, there may be some merit to Ethnan's suggestion.

because this is a solar panel,

Do you know something that we don't know?

 

[PRADEEP MANI]

VSD (Variable Speed Drive) and Star-Delta are typically used as redundant systems, commonly found in data centers and other critical applications. If a VSD fails, the replacement process can be time-consuming. In such cases, other conventional starters are used to reduce downtime and minimize production losses.

 

[jraef]

Star connection is better for low loads. If your pump is below 5KW, then you have lower current in each line, and low starting torque required.
A star connection will draw less current at start than a delta connection, and because this is a solar panel, your power is limited, so go star connection.

That would be pointless with a VFD. The Star current would be less, but the torque would be severely limited. The VFD can achieve the same reduction in current without losing torque. So the Star-Delta would be pointless in that regard.

If the S-D is still connected and active (meaning not just left abandoned in place from an older system as waross suggested), it is more likely that it is there as a BYPASS for the VFD in case the VFD fails. If the motor is large for the available power, and they want to continue running at full speed if the VFD fails, then they will need a reduced voltage starting method of done kind. S-D is the least expensive option for that in some cases (although I find that Solid State Soft Starters are often more cost effective and simpler).

 

[LionelHutz]

A star connection will draw less current at start than a delta connection, and because this is a solar panel, your power is limited, so go star connection.

The star-delta starter only makes sense if it is the only starting method.

A VFD will draw even less line current than a star connected motor directly connected to line power. The VFD will even draw less line current than the motor draws connected on the VFD output while the motor is accelerating. the input current will only rise to be a close match to the motor current when the VFD gets the motor close to full speed.

It is completely pointless to switch between star and delta motor connections on the output of a VFD. The control panel should not be using both methods together.