OT Three phase power generation

do you have the same problem with each generator ??

voltage is directly proportional to the amps (current)

should be able to run fine with a unbalanced load as long as the load doesnt exceed the maximum of any phase of the genny

the unbalanced load will have effect on three phase equipment but and its big but your unbalanced supply will have a big effect your supply has to be right and its not real flash

It isnt normal to have a unbalanced supply but you will never have a balanced load even if you ran mainly 3 phase gear off it the control circuitry is still single or 2 phase so you never have a balanced load
power supply coming down your street is balanced and the voltages are the same across the phases yet the loads are not balanced and change constantly across the phases as people turn things on and off

dunno what your talking about with hot starts ???? star and delta on a motor if the terminal block is ok for, star the three bars are at the bottom or top three studs, for delta the three bars are on running vertically on the studs

dunno if any of this helps but your problem is more of a supply problem than anything else as in a genny problem

Paul

do you have the same problem with each generator ??

voltage is directly proportional to the amps (current)

should be able to run fine with a unbalanced load as long as the load doesnt exceed the maximum of any phase of the genny

the unbalanced load will have effect on three phase equipment but and its big but your unbalanced supply will have a big effect your supply has to be right and its not real flash

It isnt normal to have a unbalanced supply but you will never have a balanced load even if you ran mainly 3 phase gear off it the control circuitry is still single or 2 phase so you never have a balanced load
power supply coming down your street is balanced and the voltages are the same across the phases yet the loads are not balanced and change constantly across the phases as people turn things on and off

dunno what your talking about with hot starts ???? star and delta on a motor if the terminal block is ok for, star the three bars are at the bottom or top three studs, for delta the three bars are on running vertically on the studs

dunno if any of this helps but your problem is more of a supply problem than anything else as in a genny problem

Paul

Seems reasonable to me that if there's about half the load on one leg the voltage on that would be higher.

Sounds like it's hooked up with all of the 1 phase loads on one leg which isn't optimal - they should be distributed more or less evenly on all 3.

I'm not an expert by any means, but I fell like I've heard before that it's not good to have the machine that much out of load balance. I think some unbalance isn't a big issue, but if it's enough that you're seeing a voltage drop like that it's probably something that should be fixed.

Having to adjust the alarm points is worrying though since this would indicate things are changing to cause the unbalance - have they been rewiring or something that would shift loads around?

Hello everybody thank you for the inputs, I was hoping it would be more of a distribution problem than a supply problem as mrsmackpaul said and I believe its true, I talked with another company today and they said to try the same thing you mentioned which was try firing up the spare generator and seeing if the voltage differential shows up as well, he says if the voltage regulator in the gen is set up to only monitor a certain leg in the gen then that leg will have correct voltage but the others will not he says the best bet is to try and balance the load which may be easier than I thought. I originally believed that you used two legs of the gen to make single phase but after looking at Wikipedia it says the best way to pull single off of a three phase gen is to run it in a wye configuration where you only take one leg of the gen and a neutral and transform it down to the required voltage so it should be fairly straight forward I think just moving some of the heat trace circuits around between the different transformers. The guy also said that you could get a different voltage regulator or convert the current one to a three phase sensing VR and it will make an average voltage of all three legs where in one may be 490v and the other two may be 470v instead of the current configuration with one leg at 480v and the other two at 440-450v. This is a hotstart http://www.hotstart.com/assets/Data-Sheets/Data-sheet-OCLE-DS-OCLE-E.pdf for those that were curious. Its a pump, 480v 3ph motor, and 480v 3ph electric heating element combo what it does is when one of the compressors is shutdown be it either a fault or normal maintenance, the hotstart is turned on automatically by a relay and it begins to recirculate the engine oil and the coolant (separate pumps motors and elements for each) through the engine and through control circuitry it maintains them at a set temperature 120 deg f for coolant and 100 deg f for oil, this is to allow for easier startup and to ensure that at startup oil gets where it needs to go as quickly as possible. I had read somewhere today not to run three phase motors on more than a 2% imbalance which at our current configuration I have an 8% imbalance so now it makes sense why ive been seeing motor protection switches being popped and the lack of voltage therefore more amperage explains the breakers being tripped. This stuff makes me nervous ha ha ive been bitten by 120v before I cant imagine what 480v would do. This problem all arose a couple years ago when the customer decided to add electric heat trace to the rest of their process gas piping and I mean lots of it, I think the eletricians went through several rolls of it probably thousands of feet and just no one has bothered to look into it the customer owns the generators and I just maintain them and it hard to convince them to change anything since "its been working that way for a while now why change it". Thanks for all the input guys its kinda fun learning this stuff.

Don't think there is any practical advantage to tapping line to neutral for single phase (277 volt) vs line to line (480 volt). Just as effective (and easier if you have 480 transformers already) to simply balance the loads across the 3 phases by adding additional transformers that tap the lightly loaded phase. For example there may be a single transformer tapped on phases A and B that feeds all the heat trace and other single phase loads. Adding 2 more single phase or a single 3 phase transformer so load is tapped on A and B, B and C, A and C should go a long way to resolving your voltage problem.

The reconfigurable hot starts probably are intended to change the voltage requirement of the hot starts themselves, not be adjusted for the generator being configured as either Y or Delta. In almost every situation, a generator can be considered a "black box" that produces the desired voltage at the desired frequency. Doesn't matter whether it is Y or delta as long as it makes 480 3 phase 60 Hz. ........... unless you need 277.......then it has to be Y......or you have to have a transformer.

Balance the single phase loads(heat trace) across all three phases as this will cure the problem properly. Switching from a single phase sensing to a three phase sensing will raise your voltage average(true). But it is only a bandaid not a cure! We run the 3512/16 gensets on load banks with a couple of percent imbalance because the resistance across the phases very based on age and abuse. Some customers don't like to see it with varying currents and output voltages but we are usually within 1% for voltage.
Typically CAT(KATO) generators are 277/480 Wye on the busbars so that a neutral can be generated.
The Hot Start doesn't care if its a Delta or a Wye as long as its getting 480Vac. Are these the big ones that do oil and water or the small ones mounted on the side of the skid that only do water? I run some on GE locomotive engines(3.5 MW) that are 5kw on Oil and 10kw on Water. Those babies will suck power but heat the engine Quick!

Don't think there is any practical advantage to tapping line to neutral for single phase (277 volt) vs line to line (480 volt). Just as effective (and easier if you have 480 transformers already) to simply balance the loads across the 3 phases by adding additional transformers that tap the lightly loaded phase. For example there may be a single transformer tapped on phases A and B that feeds all the heat trace and other single phase loads. Adding 2 more single phase or a single 3 phase transformer so load is tapped on A and B, B and C, A and C should go a long way to resolving your voltage problem.

The reconfigurable hot starts probably are intended to change the voltage requirement of the hot starts themselves, not be adjusted for the generator being configured as either Y or Delta. In almost every situation, a generator can be considered a "black box" that produces the desired voltage at the desired frequency. Doesn't matter whether it is Y or delta as long as it makes 480 3 phase 60 Hz. ........... unless you need 277.......then it has to be Y......or you have to have a transformer.

Yes, do not get careless with that 480, it can hurt you bad...an electrician working on a pellet mill one told me you can't leave a screwdriver burr on a screw, it will start an arc...
That pellet mill was the only big genset I've ever worked around, I mainly took care of the engine-a 16V71 Detroit...loved that motor.
Electricity-wise, I'm OK up to 24V, above that I leave it to the experts...