Phase sequence indicator

crutschow said:

A phase synchronizer can be quite simple.
For example an LED in a bridge with a simple current-limit circuit can be connected between the same phase of the two generators.
The LED will flicker if they have a slightly different frequency, but as the slave generator is adjusted to the proper frequency and phase, the LED will burn steady, and then go out when the two phases are close together in relative phase (within the threshold voltage of the circuit).
At that point it's generally safe to close the switch between the two generators.

You can use two such circuits for two of the phases, which will then also indicate if the phase sequences match.

If you told us you needed to synchronize two generators together in the beginning we could have saved a lot of wheel spinning here.

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Hi,

Wouldnt it be wise to check the phase rotation of both generators first though?

sachin88 said:

I thought if i have a sequence indicator then while connecting the slave generator with the master , dark lamp could be used for parallel operation.

Could you please help me with the circuit as you explained above for three phase generator.

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Hi,

I would check the phase rotation of both generators first to make sure you know what A, B, C are, then go from there.

MrAl said:

Wouldnt it be wise to check the phase rotation of both generators first though?

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The three incandescent lamp circuit checks phase rotation as well as phase difference, which seems to be a better and simpler circuit than my original LED proposal.
If the phase is incorrect than the lamps won't light in the expected order for either connection used for the lamps.

crutschow said:

The three incandescent lamp circuit checks phase rotation as well as phase difference, which seems to be a better and simpler circuit than my original LED proposal.
If the phase is incorrect than the lamps won't light in the expected order for either connection used for the lamps.

Click to expand...

Hi there,

Where can we find this circuit?

MrAl said:

................
Where can we find this circuit?

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That Wiki reference in my post #40 discusses the circuit.
It's simply three incandescent bulbs wired between the three phases of the two generators.

You wire all three bulbs like-phase to like-phase if you want all three to go dark when the phase order is correct and they are synchronized.

If you cross wire two of the phases then you will get one bulb going dark with the other two bulbs at equal brightness when the the phase order is correct and they are synchronized. This connection likely will give more sensitive detection of the phase difference.

Below is a simulation of the two circuits:
ABC and XYX represent the two generator signals with proper phase sequence and in sync.

R_bx represents the incandescent lamps.

R_b1, R_b2, and R_b3 are connected like-phase to like-phase and thus show zero current with the two generators in phase ( all dark).

R_b1, R_b4, and R_b5 are the alternate connection for two cross-phase connected bulbs.
With this configuration, R_b4's and R_b5's currents (and thus brightness) are equal when the phase difference is zero.

R_b1 is connected the same for either configuration and is thus dark in either case.

Note that if the phase sequences are different between the two generators then the behavior of the two circuits is reversed, thus either configuration will indicate when the sequences don't match.