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...
A drive, running ONE MOTOR in any type of vector control mode, is watching the performance of the motor and adjusting the PWM pattern going to it in order to correct any “error” between what it is being told to run the motor at, and what the sensors tell it the motor is doing. What it is...
Most likely degraded insulation and shorted turns. A bad cap generally means it doesn’t start turning, it will just sit there and vibrate back and forth until something trips. Shorted windings, especially turn-to-turn, means less impedance and thereby higher current. If you have a Megger, you...
CTs, you probably can’t use, but you can get transducers that use Rogowski Coils as the sensing elements that will work at low frequencies. They work down to <1Hz and up to I think 400 Hz.
Voltage measurements at low frequencies like 1Hz is an entirely different situation. I have never seen any...
Or… use a VFD that is about 3x larger than the motor (using CT /HD sizing). Most drive transistors on CT/HD sized drives can handle around 200% current for 2 seconds. So given that the starting current of the motor will be roughly 6x, tripling the size of the VFD should get you there. Personally...
Correct, ID Run is what ABB calls their “autotune” procedure and is necessary when running motors in any form of vector control (SVC, FVC, FOC, DTC). But you can’t do any of those control methods when you have more than one motor, you are only able to do V/Hz control, because no two motors have...
Bottom line, VFDs are not made to do this. They are transistor based devices, and the AC output is not truly AC, it is pseudo-AC, relying on the inductive time constant if the motor windings to help make it act like AC. But in the first instant that the motor windings are energized by the...
Ah, duh, two speed motor! Missed that possibility…
But although I can see them having a mechanism for disconnecting the resistors for the rotor brushes DURING the transition from one speed to the next to avoid a transition spike, it would have to reconnect them again once that’s done. So it...
Rings opening and closing is not a WRIM... If the ring circuit opens, the motor wouldn't work. Or are you talking about SHORTING the rings?
Are you sure this isn't a Repulsion / Induction motor? That's a really old, kind of forgotten technology though, I don't know why anyone would resurrect it...
An AC squirrel cage induction motor will not become a generator just by spinning with no power supplied. To generate, there must be magnetic fields involved and there are no magnetic fields in the motor yet. The rotor magnetic fields are “induced” into it by the stator magnetic fields, which are...
I’m a fan of electronic overloads, but the one place where eutectics shine is in being frequency insensitive. They make a good choice behind VFDs.
However the days are numbered for eutectic alloy overloads because they have lead in them, making it impossible to use them on anything that will be...
