Lab Information
EXPERIMENT NO. 8
DELTA-DELTA CONNECTIONS
PURPOSE:
To determine the method and necessity for the proper polarity determination in a  connection
and to show the operating characteristics of the - connection.
DISCUSSION:
In order to close the delta circuit, it is necessary that all coils must have the correct polarity.
Figure 15 shows the vector diagrams of coil voltages necessary for proper closing.
FIGURE 14
It can be seen that the vectorial sum of these voltages is zero. Therefore, if figure 14B is opened
at any H1-H2 point and a voltmeter placed between these two points, its reading would be zero.
The relationship of line and coil voltages and currents in the delta connection are shown in
Figure 15. Since the line voltage is across the coil, VL = VPH. The relationship is IL = IPH for the
line and coil currents.
APPARATUS REQUIRED:
1. Three Hampden Transformers (Model T-100-3A)
2. One Hampden RLC resistance-reactance load
3. One Hampden AC voltmeter
4. Two Hampden AC ammeters
5. Two Hampden Wattmeters
6. One portable voltmeter (rated at least 300V)
7. One Hampden three-phase, variable power supply.
PROCEDURE:
1. Make the connections shown in figure 16. Adjust the supply for 120V (line-line) and record
the reading of the meter designated VN.
2. Make the connections shown in figure 17. Adjust the supply for 120V (line-line) and record
the voltage of the VN meter.
3. Make the connections shown in figure 18. Apply a balanced load of approximately 0.3 amps.
Record all meter readings.
REPORT:
Prepare a written report to include the following:
1. The circuit schematic, voltmeter and ammeter readings, and the 3 voltage. Vector diagram
for steps 1 and 2.
2. A comparison of the measured values of the primary and secondary volts and amps, and the
secondary watts in step 3 to the theoretical values.
3. An explanation as to why the secondary connection is made in steps 1 and 2. What is the
reading of the VN meter if the secondaries remain open?
EXPERIMENT NO. 8
EXPERIMENT #8