MTW
Senior Member
- Location
- SE Michigan
What size single phase service is existing to the building, what size is the transformer feeding your building?
Rotary Phase Converter and Equalizing Voltage Output
- Thread starter Bertsbolts
- Start date
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zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
That's all ? Well, you'd still have to change the shop service disconnect and add a 3-phase panel, but that'll be a whole heap better (and cheaper in the long run) than fighting with things.
Or rent a generator for probably $6-700/week with delivery/pickup/fuel/connection-cables... if you only need that twice a year- Maybe, otherwise it's a silly way to do things.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
That's just it, how often is it needed. How often might you need 480 volts instead of 208-240? Going to need a transformer if you need both high and low volts, or a generator that can be reconfigured for either voltage.
another possibility would be generator without prime mover and drive it with a single phase motor. There are 15 HP single phase motors out there.
Rotary converters aren't exactly cheap either, if you can set up motor-generator for not too much more may be well worth it.
Bertsbolts
Member
- Location
- Florida
- Occupation
- Production Engineer - Heating, Cooling and Electrical Control Systems
240 Volt single phase. Not sure of the transformer "size", but we have a 300A service to the building. It is split 150A in the office, and 150A in the shop. The place used to be a cabinet shop. When we bought the lace, we were building on boiler sets, heat exchangers, and pump sets. Today, we have gotten into doing Heat Pump/Cooling and Low Temp Cooling with refrigeration condensers for the latter. We have our own trademarked dual pass DX heat exchanger for these. The 150A in the shop is also a problem when trying to operate some of the larger equipment with other things being "lit up". In the past few days, I have finally convinced the "ownership" that a service upgrade is in order. We have since consulted with the utility, and I am getting quotes from contractors. I have also somewhat convinced them of having a propane generator with 100A capacity, with voltage selections of 120, 208, 230, 240, 460, and even to 575. (we do some overseas things now and have a certification standard with Canada and Mexico). Another part of the decision is now to maybe get the utility upgrade and a three phase variac To go with the digital converters, or a single to three phase variac, which costs a bit more, but less than the two former items commbined. . I got some help from the Mfr. Tech Rep on that one. The condenser mfr. told them they have the variacs because of UL testing requirements. Since we could be heading there, might be time to get set up. Crossing my fingers that "sense" prevails.
"Tripping over dollars to pick up pennies"
Bertsbolts
Member
- Location
- Florida
- Occupation
- Production Engineer - Heating, Cooling and Electrical Control Systems
Yep. See my reply to MTW. The last line of the reply. That is what I am fighting. (And I sometimes don't know why I bother
)
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Can a VFD be used to cover those voltages and both 50 and 60 Hz?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
VFD's are good for driving motors only, and when more than one motor they all need to start/stop at same time. They especially don't like having switches/contactors on load side and adding/removing loads to an active output.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I was thinking about for Bert's testing setup.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
But isn't he driving multimotor and combination loads? That is part of why I mentioned it.
If he uses a VFD to directly drive a single motor load he will be fine, if he is powering multi-load HVAC units and wants this for a general purpose supply, a VFD won't like switching loads into an active output, and any non motor loads won't necessarily play well with it either.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I have no idea.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
From bits of information I have seen, he may have some instances where he maybe only powering an individual compressor, but possibly has cases where powering multi - load pieces of equipment, and the controls for them. Sounds like all this is in the shop testing , not sure if for new units or for testing after repairs, how useful might depend on the reason for testing. Might be able to rig it up so that you only drive say a three phase compressor with the VFD and power anything else from the single phase source, which may be handy if they are repairing units. In those cases you might even bypass phase monitors if you had to. If performance testing new or even fully refurbished units might be more desirable to have an actual three phase supply?I have no idea.
MTW
Senior Member
- Location
- SE Michigan
Burt, some thoughts about your current setup and going forward. First off is why I asked about your existing service size and pole transformer. Because you replied 300A without a pole transformer size, makes me wonder. Adding up mains in the building usually do not equate to the actual transformer capacity out on the pole, because the utility normally runs them hot, way over the NEC accepted KVA values. Drops to the building are usually sized the same way, by the utility. My guess is you likely have a 200A service, with a thru the meter setup, meaning all of the current goes directly through the meter, then split to two main disconnects. In my area they now offer 320A through the meter single phase services, but that is relatively new, not something you would find on an older service. Anything bigger would require a CT (current transformer) meter cabinet which you didn't mention.
That said, when you convert from single phase to three phase you have to divide the 1Φ current capacity by the √3 or 1.732. That makes the shop service 150A capacity 150/1.73 = 86A @ 240V 3Φ. That figure does not include any losses from conversion equipment or your other shop loads. If your manufacturing the systems there, in the same building with shop equipment it's not a good starting point. When you cut that 86A in half for conversion to 480V equipment testing, 43A 480V 3Φ is a pretty low number. And remember that figure doesn't include conversion equipment losses, transformer losses, or shop equipment loads. And then as a rule of thumb, for RPC's the converter should be sized at 1.5 x the load HP for full performance. The phase perfect's are rated differently than a RPC but still have conversion losses. Also be aware, from what I am told, the phase perfect's require capacitor replacements on a three year schedule, or bad things can happen to the equipment loads. They have changed their designs in the last couple of years, so you may want to look at their service manual to confirm any changes in their requirements.
So your existing 10HP 480V RPC is generally only rated for a 6.6HP 480V 3Φ load. That is if it is properly fed, and excludes other shop loads. Using it to run bigger loads will typically result in poor performance and load starting problems, especially with compressors starting against any head pressures.
If it were me as your contractor I would push for 480V 3Φ 4W wye as the standard shop voltage and covert from there as the needs arise. Putting in a bigger single phase service at low voltage, or even worse a propane generator that needs re-strapping for each voltage, expensive fuel, siting space and additional wiring sounds like a waste to me. If you were to change the service to 480V 3Φ then you would need one transformer to feed your existing building and equipment loads. I would tell the owner that investing in the building service upgrade would add to the building value for a future sale or for an upgrade to a larger facility if the business continues to grow. I have done a few of these conversion projects over the years on some fairly large manufacturing facilities, converting the building service, existing building loads and the manufacturing equipment to a higher voltage for more capacity. Believe me I've heard plenty of belly aching from the front office, I usually tell them to fire me and find someone cheaper if they think it cost's too much. I have also later gotten kudos from them, when they wanted to add additional equipment and discovered that I put in extra switchboard switches and underground conduits to areas that they swore was only going to be used for material storage. It's 100% cheaper to add the things before their needed, than to wait till it's a necessity and have to rework the service again for the third time and run more circuits across a fully occupied building.
Some ideas for thought, on supplying different voltages for testing equipment. If you start with 480V wye things become easier, smaller, and generally cheaper as that is the standard voltage for most standard transformers and heavier equipment loads. At low voltage everything has to double or more in size, that increases cost and size of space required, never a good thing. With a wye system as the origin, you can get an testing auto-transformer that will cover all of the voltages you need in one unit, which is not readily available with a delta system. Just about every piece of equipment made will run without issue on a wye system as it's now the world standard, not so much with a delta system which requires study and work around's or worse equipment damage if you don't do it. This is especially important with VFD's as they are becoming the standard on energy efficient equipment, and that is the field you are in.
Some examples for you to consider.
Dongan 3Φ multi-volt auto-transformer. All the voltages you will ever need. Bad part is reconnecting for every voltage change.
https://dongan.com/product/
For more rapid voltage change-out with less possibility of damage changing connections you can get a custom unit with a selector switch. Here is an example from a local builder that I have used their products before. The one in the photo example looks to be an open delta configuration with just two coils, which I don't recommend for your use, you want that wye output.
https://www.powertran.com/#
While doing the Powertran examples, here is one that is a step up unit that could be powered by a standard delta 240V phase perfect or RPC unit and get at 480V wye with adjustable input taps.
Here is other custom manufacturer's that builds testing transformers to fit your needs, but you need to call for information on their designs. https://www.olsun.com/olsun-product-information/
https://americas.hammondpowersolutions.com/en/products/specialty/autotransformers
I have designed and built a couple of multi volt output test boards using the open delta transformer connections for my own shop and my local motor shop for testing motors and various pieces of equipment. As I said earlier I don't recommend delta for your specific use, but the designs used interlocked contactors to utilize one output connection and a control selector switch to select the output voltage. The controls were interlocked to provide one voltage at a time on the output. The motor shop wanted a start/stop for each voltage, for my own use I wanted a single start/stop and a selector switch for switching voltages on the fly. The motor shop has a 480V wye service, my shop has a 240V delta with the high leg. The output voltages ranged from 120V 3Φ (great for starting large motors laying loose on the floor, so they don't take off rolling across the shop), 208V, 240V, 480V. If 400V or 600V is needed, which is rare, I use a stand alone transformer connection for that, powered by the test stand.
A couple of last points. I think your manufacturing rep is a bit off on a couple of his points, not to deride him, as he's be helpful to you, but to keep you pointed in the right direction. One was the comment about your existing RPC being a 480V wye with a high leg, that does not exist as kwired pointed out to you earlier. It's a delta with the high leg as I pointed out the voltages in the illustration earlier, a pretty rare output, generally known only to 480V RPC's. The second thing that comes to mind is mention of a Variac that converts 1Φ into 3Φ. If such an device existed, then you could just use transformers to convert 1Φ into 3Φ. I have a couple of motorized 3Φ variac's as part of my payment from the motor shop, and if they could be used for phase conversion I would be all ears.
https://variac.com/staco_Variable_Transformer_Map.htm
One other thought about your phase monitor on certain model compressors. It seemed, from your post, that your understanding is incorrect about placing the wild leg. I would encourage you to look up the installation instructions for the phase monitor. With your units working properly with the wild leg placed on L3, that tells me that L3 is not monitored, and that really it is only monitoring the other two legs, because at unloaded voltage, your generated leg is way out of bounds, which is hard on motors. Likely it was designed that way, to function on delta high leg systems. As mentioned earlier, only use L1 & L2 to change rotation.
Lastly, I forgot to mention earlier when I told you to use a standard 240V RPC or Phase perfect and put the step up transformer on the output, the transformer needs to be disconnected until the RPC or Phase Perfect gets up, running and stabilized, before you bring on the transformer and then the load.
That said, when you convert from single phase to three phase you have to divide the 1Φ current capacity by the √3 or 1.732. That makes the shop service 150A capacity 150/1.73 = 86A @ 240V 3Φ. That figure does not include any losses from conversion equipment or your other shop loads. If your manufacturing the systems there, in the same building with shop equipment it's not a good starting point. When you cut that 86A in half for conversion to 480V equipment testing, 43A 480V 3Φ is a pretty low number. And remember that figure doesn't include conversion equipment losses, transformer losses, or shop equipment loads. And then as a rule of thumb, for RPC's the converter should be sized at 1.5 x the load HP for full performance. The phase perfect's are rated differently than a RPC but still have conversion losses. Also be aware, from what I am told, the phase perfect's require capacitor replacements on a three year schedule, or bad things can happen to the equipment loads. They have changed their designs in the last couple of years, so you may want to look at their service manual to confirm any changes in their requirements.
So your existing 10HP 480V RPC is generally only rated for a 6.6HP 480V 3Φ load. That is if it is properly fed, and excludes other shop loads. Using it to run bigger loads will typically result in poor performance and load starting problems, especially with compressors starting against any head pressures.
If it were me as your contractor I would push for 480V 3Φ 4W wye as the standard shop voltage and covert from there as the needs arise. Putting in a bigger single phase service at low voltage, or even worse a propane generator that needs re-strapping for each voltage, expensive fuel, siting space and additional wiring sounds like a waste to me. If you were to change the service to 480V 3Φ then you would need one transformer to feed your existing building and equipment loads. I would tell the owner that investing in the building service upgrade would add to the building value for a future sale or for an upgrade to a larger facility if the business continues to grow. I have done a few of these conversion projects over the years on some fairly large manufacturing facilities, converting the building service, existing building loads and the manufacturing equipment to a higher voltage for more capacity. Believe me I've heard plenty of belly aching from the front office, I usually tell them to fire me and find someone cheaper if they think it cost's too much. I have also later gotten kudos from them, when they wanted to add additional equipment and discovered that I put in extra switchboard switches and underground conduits to areas that they swore was only going to be used for material storage. It's 100% cheaper to add the things before their needed, than to wait till it's a necessity and have to rework the service again for the third time and run more circuits across a fully occupied building.
Some ideas for thought, on supplying different voltages for testing equipment. If you start with 480V wye things become easier, smaller, and generally cheaper as that is the standard voltage for most standard transformers and heavier equipment loads. At low voltage everything has to double or more in size, that increases cost and size of space required, never a good thing. With a wye system as the origin, you can get an testing auto-transformer that will cover all of the voltages you need in one unit, which is not readily available with a delta system. Just about every piece of equipment made will run without issue on a wye system as it's now the world standard, not so much with a delta system which requires study and work around's or worse equipment damage if you don't do it. This is especially important with VFD's as they are becoming the standard on energy efficient equipment, and that is the field you are in.
Some examples for you to consider.
Dongan 3Φ multi-volt auto-transformer. All the voltages you will ever need. Bad part is reconnecting for every voltage change.
https://dongan.com/product/
For more rapid voltage change-out with less possibility of damage changing connections you can get a custom unit with a selector switch. Here is an example from a local builder that I have used their products before. The one in the photo example looks to be an open delta configuration with just two coils, which I don't recommend for your use, you want that wye output.
https://www.powertran.com/#
While doing the Powertran examples, here is one that is a step up unit that could be powered by a standard delta 240V phase perfect or RPC unit and get at 480V wye with adjustable input taps.
Here is other custom manufacturer's that builds testing transformers to fit your needs, but you need to call for information on their designs. https://www.olsun.com/olsun-product-information/
https://americas.hammondpowersolutions.com/en/products/specialty/autotransformers
I have designed and built a couple of multi volt output test boards using the open delta transformer connections for my own shop and my local motor shop for testing motors and various pieces of equipment. As I said earlier I don't recommend delta for your specific use, but the designs used interlocked contactors to utilize one output connection and a control selector switch to select the output voltage. The controls were interlocked to provide one voltage at a time on the output. The motor shop wanted a start/stop for each voltage, for my own use I wanted a single start/stop and a selector switch for switching voltages on the fly. The motor shop has a 480V wye service, my shop has a 240V delta with the high leg. The output voltages ranged from 120V 3Φ (great for starting large motors laying loose on the floor, so they don't take off rolling across the shop), 208V, 240V, 480V. If 400V or 600V is needed, which is rare, I use a stand alone transformer connection for that, powered by the test stand.
A couple of last points. I think your manufacturing rep is a bit off on a couple of his points, not to deride him, as he's be helpful to you, but to keep you pointed in the right direction. One was the comment about your existing RPC being a 480V wye with a high leg, that does not exist as kwired pointed out to you earlier. It's a delta with the high leg as I pointed out the voltages in the illustration earlier, a pretty rare output, generally known only to 480V RPC's. The second thing that comes to mind is mention of a Variac that converts 1Φ into 3Φ. If such an device existed, then you could just use transformers to convert 1Φ into 3Φ. I have a couple of motorized 3Φ variac's as part of my payment from the motor shop, and if they could be used for phase conversion I would be all ears.
https://variac.com/staco_Variable_Transformer_Map.htm
One other thought about your phase monitor on certain model compressors. It seemed, from your post, that your understanding is incorrect about placing the wild leg. I would encourage you to look up the installation instructions for the phase monitor. With your units working properly with the wild leg placed on L3, that tells me that L3 is not monitored, and that really it is only monitoring the other two legs, because at unloaded voltage, your generated leg is way out of bounds, which is hard on motors. Likely it was designed that way, to function on delta high leg systems. As mentioned earlier, only use L1 & L2 to change rotation.
Lastly, I forgot to mention earlier when I told you to use a standard 240V RPC or Phase perfect and put the step up transformer on the output, the transformer needs to be disconnected until the RPC or Phase Perfect gets up, running and stabilized, before you bring on the transformer and then the load.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
MTW
Senior Member
- Location
- SE Michigan
That part is true, but if your driving a packaged control system, with a VFD, that won’t work very well either. Good for a motor load, but not for packaged controls.
The phase perfect he is considering, is a blend of the two technologies. Its a static phase converter similar to a VFD, it passes through the two utility legs, and generates the third leg. But just like a VFD it needs to be powered up before you can put a load on it. On the other hand, unlike a VFD, it can do across the line starts, no need to ramp to speed, and it can drive a transformer on it’s output, as well as packaged controls. But it comes as a premium cost.
The phase perfect he is considering, is a blend of the two technologies. Its a static phase converter similar to a VFD, it passes through the two utility legs, and generates the third leg. But just like a VFD it needs to be powered up before you can put a load on it. On the other hand, unlike a VFD, it can do across the line starts, no need to ramp to speed, and it can drive a transformer on it’s output, as well as packaged controls. But it comes as a premium cost.
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