Three phase vs single phase motor

V

VermontDale

New member
We are about to upgrade our shop to a CV 1800. We have three phase wiring available in the shop.

Question: Which is the better choice, single phase or three phase?

Our particular concern is how often we can start the cyclone without overheating problems. We have an EcoGate control box which turns the cyclone on each time you start a tool. We have multiple users with much of the work done using the table saw and miter saw so the cyclone can be turned on many times per hour.

Does three phase have an advantage in this situation?

Are there important choices concerning the specs for the starter box for the three phase system?

Is "soft start" using resistors to limit the current during start up a viable option?


Dale
 
Dale,
I take it that you will have single phase 120/240 volt service as well as 3 phase 120/208 service.(?). The impeller on the CV1800 is heavy and it takes a while for the motor to come up to speed. Single phase motors do not start on their own so they include a starter winding with capacitors and a centrifugal switch for starting. They are not usually made for frequent starting and the capacitor(s) will fail if started too often. Single phase motors used in special cases like gas pumps, which are started many times an hour, have more rugged starting circuits. Three phase motors develop rotary motion naturally so they do not require special starter windings. They do take extra current (surge) during startup so stress is placed on the motor. For small motors like 5 HP and less magnetic starters (contractors) typically are used without any soft start features. I am of the opinion that the cyclone should be turned on at the beginning of operations and left running between operations. If you run a laser particle counter you will see the count rise immediately upon any wood processing operation, continue to rise during the operation, and then begin to fall after the operation. No matter how hard you try some dust will escape collection and the cyclone will eventually capture it if you keep it running. I hope this helps.
bababrown
 
three phase motor

three phase motor

Thanks Baba,

Your comments on the three phase vs single phase motors sound right to me. I actually took a course or two in motors and generators in the 1950's. But I spent my whole EE career in electronics so I have forgotten most of my motor material.

Whether we can leave the cyclone running for long periods of time will depend upon the noise level we achieve. We also have a Delta Air Cleaner and an exhaust fan which we can use.

I am still interested in the "soft start" approach. Are you familiar with people who have done this successfully with a three phase motor on a cyclone?

Also, there is the question whether to add resistors or buy a commercial soft start control box.

Dale
 
Dale,
It sounds like we have a lot in common. I spent 34 years in electronic countermeasures as an EE and I'm also an old guy with some motor courses at Penn State in the early 60's. For low noise I would recommend you build a closet on the outside of your shop for the cv1800 and feed the air back in thru an opening. With my "Wart" install the noise from the cyclone is like a distant whine and the noise in the shop is almost entirely from air noise at the hoods. I have the noise results in my section of the photo gallery. I don't know of anyone using soft start controllers. There have been a few foreign installs using inverters on 50 cycle power. There is a ton of info on soft start, you might start on automationdirect. Good luck,
bababrown
 
Hi Dale

I also have a Greengate Controller which I will use with my new CV 1800.

I believe you can adjust the run time after the last gate is closed. Increasing the time the CV is kept running to clear the ducts will reduce the number of start stops because sometimes the CV will still be running when next someone starts a machine.

The easiest and cheapest way to get a soft start on the CV is to use a 3 phase motor and a VFD. The VFD can be programed to have an extended ramp up to speed time which is an effective soft start
Cheers
Ron
 
VFD for 5hp three phase motor

VFD for 5hp three phase motor

Hi Ron,

We will be using a three phase motor. It is a beast, 100 lbs rather than 50 lbs for the single phase motor. But it should be much more reliable.

Could you provide me more info on your VFD? For example, manufacturer, model and approximate cost. I have done some looking on the internet but haven't found the right thing yet.

Thanks,

Dale
 
Dale
3Ph motors are normally smaller, lighter and more compact than 1Ph motors.

The VFD that the Australian Distributer for CV supplies is a POWTRAN brand 4Kw 3Ph model ( PI9100A 004G3 3Ph 380V model)) and he can supply them for either 3Ph or 1Ph input. These and other brands are readily available on eBay for about $Au350.
Note that the 1ph model is rated 220/240 V while the 3Ph model is 380V 50/60Hz. Normally the 3ph model is preferred because of the lower input current and you do not have to derate the VFD because of the 1Ph input. Many VFD manufactures recommend derating there VFD's when fed with 1Ph Power. All VFD's ( both 1Ph 240V and 3Ph 380 V input) output 3Ph power and require 3Ph motors

Which ever model you choose you will need a 3Ph motor that operates at the appropriate voltage. Most Vfd's output the same V as the input V. Most modern 3Ph motors are dual voltage and can easily be wired Star or Delta to suit.

You will also need a very small Relay to allow the Ecogate to switch the low voltage (24V) control circuit of the VFD from run to stop. You MUST NOT switch the output of the VFD directly as this will destroy the VFD. That is the relay switches the VFD low voltage control circuit not the 3Ph high V power lines. I am in the process of sorting this out on my VFD at the moment and may be able to assist with the low voltage wiring diagram if you require.
Hope this helps
Ron
Ron
 
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