2-4-13 Phase Sequence (A)

*Rotation meter conductor leads are normally engraved ? .

1, 2, and 3

A 120/240-volt service is connected from a delta banked secondary. To reverse the rotation, only the ? phases(s) can be swapped.

120 V

*For a 3-phase generator, there is/are only ? possible direction(s) it can turn.

2

The rotation of a 3-phase motor can be changed by changing any two of the service leads on a delta service such as one providing 3-phase ? or ? .

240 V / 480 V

When replacing a pole that has a 3-phase takeoff, it is always better to make the corners so the phasing will be A, B, C, with A phase on the roadside.

False

*Normally, in new construction, the customer's electrician takes care of proper rotation to the customer's motors.

True

*When using a 3-phase induction rotation meter, it is important to get into the habit of placing the leads in the same order every time (normally left to right), and to make a notation of phase rotation.

True

Meters, instruments, and relays on 3-phase circuits depend on proper rotation to operate correctly.

True

*A transformer bank has been replaced. ? to check the phase sequence to be sure the customer's 3-phase motor will turn in the same direction as before.

Use a rotation meter

Rotation leads are normally placed 1, 2, and 3, ? when taking a rotation reading on the top of a meter base.

left to right

If equipment is protected by phase sequence relays, the equipment will not work and it may ? if its rotation has been reversed.

lock itself out

*A 3-phase waveform will ? if the sequence is changed from 1-2-3 to 2-1-3.

not change

*It is essential to take rotation readings when ? .

paralleling 3-phase transformer banks

*Only the ? changes when there is a change in the rotation in a 3-phase line.

phase sequence

*The order in which voltage waveforms reach their peaks is referred to as ? .

phase sequence

*A good way to check if the rotation meter is working properly is to swap two-rotation meter leads. The rotation meter should ? .

reverse rotation

Voltage and current magnitudes remain unchanged when ? .

rotation is reversed

*If a phase rotation reading is taken at the customer's service entrance before an outage, the next reading should be taken at the ? when service is restored.

same point

*The order in which the voltage waveforms of a polyphase AC generator reach their respective peaks is called the phase ? .

sequence

*One advantage a 3-phase motor has over a single-phase motor is that ? for the same horsepower capacity.

the physical size is smaller

It is necessary to check rotation on circuits that serve motors ? .

when the circuits are to be tied together