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Topic Title: Can generators with different phase rotation (CCW and CW) be connected to the same power distribution system?
Topic Summary: what is the consequence of having generators with different phase rotation connected in the same power distribution sys?
Created On: 09 August 2010 11:35 AM
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 09 August 2010 11:35 AM
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Joined: 30 January 2010

Dear fellow engineers,

I'm doing a design on a ship's power system, and have encountered the following problems:
The MV generators are having counter clockwise rotation; however, the newly purchased LV generators are in clockwise rotation. It is impossible to change the direction of rotation from the generator supplier's side.

Can anyone shed some light on the following questions:
1. Is it possible for a system to have generators with different phase rotation connected?
2. If yes, how can it be done and will there be any problems on AVR/protection relays?

I have this idea as follow:
If the MV generator is running in A-B-C direction, and LV generator generator is running in A-C-B, can I terminate the cable at the LV generator side as A-A, C-B, and B-C? I hope you guys understands what i mean. Will this works?

Thanks in advance!
 09 August 2010 01:39 PM
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What you are talking about sounds feasable, but I think you should get someone local who is familiar with this type of work to oversee it.
 10 August 2010 03:33 PM
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Yes, if you cross B and C connections then it will phase in. You will need to synchronise the speed and voltage before you parallel the generator to the supply. To avoid reverse power problems increase the AVR volts immediately and open up the fuel rack a little to loadup the genset
 10 August 2010 05:56 PM
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you are quite correct yuan, as is acsinuk. its like any form of main, which preferably startsas L1 L2 L3, any incorrect rotation downstream, can be corrected by changing 2 lines, but as arthur says, if its your 1st time it might be best to have someone with you for confidence!
 23 August 2010 01:32 PM
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as far as synchronization is concern it is voltage and frequency match it is correct make sure before connecting anything you have synch panel or a digital scope to monitor and make sure what you are doing .Actually ABC or ACB is the coil placements at 120 deg apart 3 voltages so you can connect 0 deg voltage to 0 deg which is refer as A and so on ..........

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