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3 phaze switch question
- Thread starter insanity
- Start date
Small three phase motor switches are not something your going to find at Home Depot or Lowe's. Most wholesale electrical distributors should have what you want. They are not cheap however. Another alternative would be to use a small three pole service disconnect. These you can find at the big box stores. They are really just a big giant switch. They take up a bit more room but you can tell if it's on or off all the way across the shop.
Allen
Allen
If you are using a VFD just program your controls to the keypad on the VFD and use that for your start/ stop.Just bypass the other switches and wire your output directly to the motor.Just get a disconnect wired in on the input side of your VFD to shut all power off to both.Beware that when working on either, that the capacitors in the VFD stay charged awhile after the power is off and will still give you a bite.Once the charge light on the panel is off it is safe.Dave 
Wayne
Jeff is correct in that you will need a 3-pole switch or contactor to properly disconnect your 3-phase motor. You can use a single-pole switch before your VFD, as Sleepy suggests, if you are using a single-phase 110V input to your VFD. If you are you are using a 220V single-phase input to your VFD, then both connections are actually hot so you would need a 2-pole switch to properly disconnect your VFD. Depending on the VFD that you are using, the current drawn by the VFD might blow up a normal "light switch" that you would get from Home Depot so you may want something beefier.
I do not recommend relying on an on-off fuction controlled by your VFD. If a fault occurs in your VFD, you may not be able to turn off the power to your motor. For safety, you NEED some way to totally disconnect the power to your VFD that is located near your VFD. You don't want to have to run back to your breaker panel to shut of the power in an emergency.
If you are using 220V to feed your VFD, I can send you a USED 3-phase contactor if you reimburse me for the postage. The main contacts are rated at 600Vac, 35A continuous. The coil is 220V/240V. It is about a 4 inch cube. The terminals are exposed so you will have to mount it some kind of box. You can mount the switch to control the contactor on the front. Please remember that it would be a USED item with uncertain history. I can check it for function before sending it but no guarantees or warranties. The service department here at Toshiba just scrapped a whole bunch of older electrical equipment, mainly UPS', so their scrap bins are overflowing with stuff like this. Send me an e-mail if you want me to grab one for you.
Phil
PS: I love your signature line.
Jeff is correct in that you will need a 3-pole switch or contactor to properly disconnect your 3-phase motor. You can use a single-pole switch before your VFD, as Sleepy suggests, if you are using a single-phase 110V input to your VFD. If you are you are using a 220V single-phase input to your VFD, then both connections are actually hot so you would need a 2-pole switch to properly disconnect your VFD. Depending on the VFD that you are using, the current drawn by the VFD might blow up a normal "light switch" that you would get from Home Depot so you may want something beefier.
I do not recommend relying on an on-off fuction controlled by your VFD. If a fault occurs in your VFD, you may not be able to turn off the power to your motor. For safety, you NEED some way to totally disconnect the power to your VFD that is located near your VFD. You don't want to have to run back to your breaker panel to shut of the power in an emergency.
If you are using 220V to feed your VFD, I can send you a USED 3-phase contactor if you reimburse me for the postage. The main contacts are rated at 600Vac, 35A continuous. The coil is 220V/240V. It is about a 4 inch cube. The terminals are exposed so you will have to mount it some kind of box. You can mount the switch to control the contactor on the front. Please remember that it would be a USED item with uncertain history. I can check it for function before sending it but no guarantees or warranties. The service department here at Toshiba just scrapped a whole bunch of older electrical equipment, mainly UPS', so their scrap bins are overflowing with stuff like this. Send me an e-mail if you want me to grab one for you.
Phil
PS: I love your signature line.
- Joined
- Sep 21, 2001
- Messages
- 265
I wanted to fuse my VFD, so I bought a 2 pole contactor box at Home Depot that has two places to screw in the fuses. It is not small. I turn it on or off with the lever on the side. I like knowing that my VFD is properly fused.
Don
Good move on adding fuses to your VFD. When things go wrong, they can make a really big bang. Fuses can help limit the damage. They need to be fast fuses though, preferably "semiconductor fuses". Otherwise, the transistors will just "give their lives to protect the fuses". My co-workers were surprised that I didn't even flinch the last time a had a realy big blow-up
Everyone in the plant thought that a rifle had been fired, event those separated by several walls.
Phil
Good move on adding fuses to your VFD. When things go wrong, they can make a really big bang. Fuses can help limit the damage. They need to be fast fuses though, preferably "semiconductor fuses". Otherwise, the transistors will just "give their lives to protect the fuses". My co-workers were surprised that I didn't even flinch the last time a had a realy big blow-up
Everyone in the plant thought that a rifle had been fired, event those separated by several walls.Phil
- Joined
- Sep 21, 2001
- Messages
- 265
Gee, I thought I needed time delay. I used Buss TL. What, specifically should we use?
- Joined
- Jun 8, 2000
- Messages
- 3,140
Phil is awesome. He should have a custom title "VFD God". What a great resource for us amatures.
Thanks Phil.
John
Thanks Phil.
John
John
I don't know about being a "God". I've just worked on them for a few years and have access to people who have more field experience than I have. I just try to contribute what I can.
Don
I forgot to add that if the VFD that you are using was meant to have a 3-phase input and that you are connecting it to a single-phase input, you will have to increase the rating of the fuses by a factor of 1.73 (square root of 3). This will help avoid blowing the fused when you are just getting near full load.
That is why a lot of the VFD's have reduced output when run from a single phase supply. The input current into each of the inputs used goes up by a factor of 1.73 relative to what is flowing when it is connected to a 3-phase source.
Phil
I don't know about being a "God". I've just worked on them for a few years and have access to people who have more field experience than I have. I just try to contribute what I can.
Don
I forgot to add that if the VFD that you are using was meant to have a 3-phase input and that you are connecting it to a single-phase input, you will have to increase the rating of the fuses by a factor of 1.73 (square root of 3). This will help avoid blowing the fused when you are just getting near full load.
That is why a lot of the VFD's have reduced output when run from a single phase supply. The input current into each of the inputs used goes up by a factor of 1.73 relative to what is flowing when it is connected to a 3-phase source.
Phil
- Joined
- Sep 21, 2001
- Messages
- 265
Thanks Phil. I hope our wanderings are helpful to Insanity. I have an Allen Bradley 1305 AA12 , which can be wired either single, or 3 phase. The AB manual is very good in providing the information about this. The drive is rated for 3HP, but we have to be careful, because the 3HP is for 3 ph and the drive is only rated for 2HP with single phase input. Thanks for the input 1.73 factor.