advice on UPS.

[electrofelon]

That's my point. He might be fooled into believing line-interactive/ offline UPS works like a dual-conversion UPS. There are a lot of sharks prowling the electric equipment market nowadays!

We are only looking at double conversion or "online" UPS, sorry about the confusion if I wasn't clear on that.

 

[electrofelon]

Does component 3. containing a vacuum pump only have the motor that's shown in your picture for an electrical load, and no other internal loads? The reason I ask is that a mass spectrometer will need additional pump(s) to lower the pressure even further than a low RPM roughing pump, such as a turbomolecular pump running at very high RPM or a diffusion pump, and maybe associated controls. If you use a VFD you'd only want to connect it to the motor in your picture and not to other loads that might need a constant 50 Hz.

Bonitron has systems providing "Uninterruptible Power for Drives":
https://www.bonitron.com/complete-systems
https://www.bonitron.com/undervoltage-cs-battery.html

Yes that motor is the only item in #3. Perhaps the "main instrument" has another vacuum pump integral to it, I don't know.

 

[synchro]

Yes that motor is the only item in #3. Perhaps the "main instrument" has another vacuum pump integral to it, I don't know.

That's good. If they have a high RPM turbomolecular pump it would have to be running off of an inverter, and so there won't be an across-the-line locked rotor current to contend with.

 

[electrofelon]

If the mechanical load presented by the vacuum pump allows it, perhaps a VFD could be used to create the 50Hz and also reduce the peak current required for starting the motor. A sine wave filter would be needed reduce any conducted switching noise. A UPS will have a PWM inverter inside of it like a VFD does, but it has filtering to provide a sinewave output. The manufacturer of the mass spectrometer might be consulted whether there could be a possible interference issue when the vacuum pump was operating on a VFD with a sine wave filter. If the vacuum pump just needs to pull a vacuum initially before the equipment is operated, then interference might not be a concern.

Perhaps the sensitive loads of the main machine and RF generator could both be placed on one single-phase UPS. And another UPS (single or 3-phase) could then feed a VFD to provide isolation from the other equipment.

Synchro,. I am leaning more toward this option. We were ready to go and had an order a UPS that would handle everything, but then they came back and said someone had beat us to the last one. It seems like everything else is substantially more expensive. They do still have the 20 KVA but I am not sure if that will start the vacuum pump. But I like the idea of just getting a vfd to soft start the vacuum pump looks like something to do that is only 3 or $400, much less than the cost increase to go from the 20 to the 30 UPS ($1300 more).

So can you talk more about this sine wave filter? It would go between the ups and the vfd?

 

[synchro]

If a sine wave filter was placed on the output of the VFD, it could filter out the rail-to-rail switching noise from the VFD output that might interfere with the sensitive parts of the equipment. There could be radiated and well as conducted interference. And so the VFD output conductors should be shielded or be in conduit. Ferrite chokes could be used to reduce the common-mode high frequency noise. I haven't priced sine wave filters, but they are not going to be cheap.

You might see if the equipment vendor can provide any information about any susceptibility of the equipment to interference, and if so, recommendations or guidelines that should be followed to alleviate it.

Will the vacuum pump motor be located very close to the more sensitive devices, perhaps even in the same enclosure? If the vacuum pump could be physically separated from the other parts of the instrument, that could help reduce coupled noise. Also, the VFD itself could be placed in a metal enclosure to shield it. If the VFD is powered by the same UPS as the rest of the instrument, then that could be another pathway for conducted noise that might need to be filtered out.

A soft starter has the advantage that it should not produce interference once the motor is started and it's in bypass mode. However, even though a soft starter reduces the RMS starting current, there may still be peak instantaneous currents that are quite high when the SCR's turn ON. It's possible the UPS might not handle that well unless it is sized sufficiently for such peak currents.

 

[electrofelon]

Update:. So we ended up going with the 30 KVA double conversion UPS that will also output 50 hertz. It has worked flawlessly so far, no issues running that vacuum pump. Turns out we are only running about 7 amps with everything running which is less than we thought. This is because the draw for the main machine took into account using a bunch of heaters that they use for the commissioning process when they first pump the vacuum down.

The machine itself is quite finicky and is taking a long time for them to get set up and operating and in fact they are still not there. A couple weeks ago we had a scare, thought our ups melted down. We got a call saying the machine shut down and they heard some arcing sounds and it smelled like burnt Chinese electronics. It turned out to be a contactor in their machine that had a bad connection so it wasn't on us. Good times.

 

[Jraef]

So too late now, but for future reference another alternative is that you could have separated out the vacuum pump, used a single phase UPS for the other stuff, then a VFD for the vacuum pump. You can get a battery backup for the DC bus of the VFD.

Bonitron UPD Battery Solutions

Bonitron's Battery UPD systems provide economical backup power to bridge power failures up to 15 minutes - avoiding downtime and enabling dark starts.

www.bonitron.com

 

[electrofelon]

So too late now, but for future reference another alternative is that you could have separated out the vacuum pump, used a single phase UPS for the other stuff, then a VFD for the vacuum pump. You can get a battery backup for the DC bus of the VFD.

Bonitron UPD Battery Solutions

Bonitron's Battery UPD systems provide economical backup power to bridge power failures up to 15 minutes - avoiding downtime and enabling dark starts.

www.bonitron.com

The machine is three phase also. There are actually no three phase loads, but its single phase loads are pulled off the three phases - and I am NOT rewiring that machine.