There is a special “voltage doubler” circuit added to the front end of the drive that boosts the DC from 165VDC to 330VDC. So as far as the inverter portion does, it’s no different.
The voltage doubler is typically limited to about 1-1/2HP max, but only because after that, it becomes...
Also, simple reversing, which is more complex with single phase motors. With a VFD on a 3 phase motor, you just give it a reverse command, no contactors involved.
With Sensorless Vector Control, which is standard on most VFDs now, you can get full torque at the outset, you no longer need to use...
I don’t understand the objection by the electrician to the step-up transformer…
Is someone thinking of using only 2 legs of a 3 phase 240 to 600V transformer? Because I can see that possibly being a problem, but just use a single phase transformer and it’s not a problem at all.
Since it is fully pneumatic, it implies you have air available. If you want to continue on with this silliness, you could put the valve into an IP65 enclosure, then use the air feed to provide a “purged air system” for the enclosure, which keeps a positive air pressure on the enclosure when the...
These are contracting statements. The term “self priming” means it does NOT need to have a priming case filled in advance if starting. You do not have a self priming pump, which is a poor choice for a sump pump. The easiest solution is it INSTALL an actual self priming sump pump.
Ah, after...
That would be pointless with a VFD. The Star current would be less, but the torque would be severely limited. The VFD can achieve the same reduction in current without losing torque. So the Star-Delta would be pointless in that regard.
If the S-D is still connected and active (meaning not just...
At this point they are not connecting to the grid, and I have warned them that using VFDs will not allow that because no VFDs I know of have UL-1741 listing, which is necessary to get a NEM contract with a utility.
Thanks everyone for the info and help.
Hey fellow drive gurus, I have one that I have never come across before. I have a client wanting to use an 40HP (30kW) 460V induction motor on a water turbine pump and have the water overhaul it to turn it into an induction generator. So far so good, I’ve done that before. But the new twist is...
It is an uninformed mechanical engineer’s term for a combination starter, ie one that comes in a box with a breaker, control switches and lights. As in “all in one package”. I’ve run across this before, it’s an HVAC thing.
I’m not sure about the torque increase part being 200%. The REASON the slip will increase is because there is already a LOSS of torque with the voltage sag, close to directly proportional to the magnitude of the voltage sag when the motor is already running (it’s worse if the motor has to start...
The way load sharing is usually done with two VFDs is to make one of them a speed follower, the the second drive is set as a torque follower to the first drive. In your case you have no control of the one on the soft starter so there will be no speed control, only torque control on the one that...
That looks to be a transformer configured for an open delta 240/120 3 phase 4 wire “high leg” system, where one pot is center tapped to provide 120/240 single phase for lights and outlets, then the other pot is straight 240, with the open delta providing 240V 3 phase for motors. Generally in...
A bespoke VFD “modified” to handle 1000V would be a nightmare in terms of spares, replacements and repairs. Low voltage drives stop at 690V, 1000V is considered medium voltage (for drives), ehere designs typically start at 2300V. So to handle 1000V, there would have to be a custom design of a...
Also better ability for the motor to cool itself at lower speeds.
As to the V/Hz issue, yes, in V/Hz mode the drive is NOT doing all the stuff I said above. My assumption was that if someone was doing an ID Run, it was because they were using vector control of some sort, and that just isn’t...
