Haha, i totally agree. This is getting ridiculous... I think i´ll go for the sensorless Vector control. I´ll add the encoders later if the load crashes xD.
One quetion though : Is it necessary to connect the VFDs between each other for torque feedback (master/slave) ?
Thank you for your answers.
Yes I agree, sorry for not saying that in the original post, but that is not an option : I want to control multiple motors through one VFD. Reason is cost and simplicity. I have gone through this discussion already (on this forum [thumbsup] ). In short: The motors...
Hi all,
I have a motor rated @ 370 W (1/2 HP), 59 N.m and 59 RPM. I would like it to run at 40 RPM and 25 N.m (=109 W) with the help of a VFD in V/Hz mode. The torque limit is for security reasons. I'd like to know the current in the motor line in order to buy the appropriate motor starters /...
Even with an 4x oversized motor ? The nominal torque is 17 N.m and the rated motor torque is 55 to 84 N.m (I have min/max speed req). And no, i cannot get a smaller motor, I'm in Peru and 0.37 kW is the smallest the manufactor has [surprise]
For the VFDs : Thanks for the heads up. What about...
@ waross : Yes, but the motors will be oversized around 3 times because we do not have smaller motors available. That means the maximum load a motor can carry is 3 times more than what the hoist can support. If we want to upsize the hoists, not only we'd have to buy new ones, but we´d have to...
@ SceneryDriver : I have just seen you comment now, soz for not responding xD.
Well this is an interesting feedback. I had not thought of that possibility. But it is a different kettle of fish - a tank can weight up to 50 tons. We also have around 30x 5t hoists lying around in the plant and the...
EDIT : "controlling" -> leveling out the torque. AND it has to stay as simple as possible : We should be able to plug motors in and out without changing any setting in the PLC or VLC configuration (The operation of setting up the lifting system should quasi be a no-brainer to avoid human errors...
For having a smooth ramp-up, for being able to control the output speed (there might be some situation where we would want to slow down the lift) and controlling the torque as far as possible.
My boss and I are pretty sure that the system would pay out, because the practical manual lifting time of one ring is about 6 hours as opposed to the 15 mins with the motors. Plus we do not need 12 persons to operate the PLC. Set up time and storage will remain the same since the motor would...
Actually, I do not need any brakes, because the hoist has an auto locking mechanism =). And even without locking : The force that is transferred to the chain connected to the motor is solely used to lift or lower the tank. The weight of the tank is only and directly transferred to the hoist hook.
Yes, I'll try to link the thermal overload to the emergency stop of all the VFD to shut down the system if any motor fails.
Here again, i'm walking in darkness. The PLC->VFD current plays a role too ?? Aaaww so many parameters !! How can a beginner possibly have knowledge of such a thing...
Before I answer, I'd like to re express my gratitude for everyone helping me here. You guys are really awesome !
@ iop995 :
Do you mean something like http://img845.imageshack.us/img845/2486/yyra.png, figure 1 ?
What is the principle behind your thought ? If I had to guess, I'd say the...
Yes, I lean towards that too, given your comments. Unless someone on the forum knows for a fact that controlling 20 motors with 4 VFD doesn't need manual correction.
That's the case. But even then, I guess interconnecting the VFD's would't bring much, because every VFD is in V/f mode. Torque...
@ Compositepro : True, i haven't thought of the situation of a motor being too slow, catching up more load and thus not being able to catch up. But how could one correct that ? Let's suppose the tank slowly tilted towards one side and 3 motors out of 10 are too (s)low. To level back all the...
Hi SceneryDriver,
Thanks for your post.
If i sum up, for each group of 5 motors we have :
In a 5 VFD configuration
5* $250 for a 2.2kW drive
= TOTAL $1250
Is it more flexible ? To get a good load distribution, we would need to connect the VFD to between each other to inter-regulate Torque and...
Thank you for the kind responses.
The system functions with a chain hoist for each motor. It would help lift up tank rings of 8 to 15m diameter, as depicted on http://www.in.all.biz/img/in/catalog/256202.jpeg
@ keith : The chain hoists have a mechanical locking which prevents the load from...
Hi everyone,
I am a student working for a company and I have an interesting task. The project consists to lift different heavy loads (15 to 50 tons) with the help of 6 to 25 motors. The amount of motors depends on mass and geometry of the load, and it should be easy for any operator to...
