electricalperson
Senior Member
- Location
- massachusetts
what are the pros and cons about an open delta system? is there a way to test to see if you have an open delta system besides looking at the pole?
open delta
- Thread starter electricalperson
- Start date
- Status
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The advantage is requiring one less transformer.
None that I am aware of, short of asking the POCO.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
One less transformer but also about 43% less output.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
There will be 0% less output if the transformer was properly sized as an open delta at the beginning.
A (2) transformer open delta bank has 57.7% the capacity of a (3) transformer closed delta bank using the same size transformers. So if the system started as a closed delta it will lose 43% of its output when it loses one transformer.
jrannis
Senior Member
- Location
- Fort Lauderdale/ Miami
I have not seen, around here anyway, the use of an open delta for anything other than 120/ 240 3 phase.
I understand that a closed delta is used aboard some types of marine vessels and the advantage being that if you loose a transformer, you would have 57.7% of the capacity of the original configuration.
electricalperson
Senior Member
- Location
- massachusetts
thanks guys
broadgage
Senior Member
- Location
- London, England
Under some circumatances it is posible to determine if a supply is open delta or closed delta, without inspecting the transformers or asking the POCO.
Accuratly measure all three line to line voltages with no or minimal load on the service.
The repeat the measurements but with a large single phase load connected between phases whilst taking the reading.
If the voltage drop on all 3 phases is similar, then this suggests a closed delta supply from either a three phase transformer, or three single phase units.
If however the voltage drop on heavy load is substantialy more on one phase, than on the other two, then this suggests an open delta service. The reason being that on one phase the current passes through two transformer windings, thus causing extra voltage drop.
For this to work, all service entrance wires must be the same size, and the transformer bank must be relativly small in relation to the service.
Accuratly measure all three line to line voltages with no or minimal load on the service.
The repeat the measurements but with a large single phase load connected between phases whilst taking the reading.
If the voltage drop on all 3 phases is similar, then this suggests a closed delta supply from either a three phase transformer, or three single phase units.
If however the voltage drop on heavy load is substantialy more on one phase, than on the other two, then this suggests an open delta service. The reason being that on one phase the current passes through two transformer windings, thus causing extra voltage drop.
For this to work, all service entrance wires must be the same size, and the transformer bank must be relativly small in relation to the service.
- Status