Need help with VFD wiring

C

Claven2

Cast Iron

Joined

Apr 28, 2008

Location

Ottawa, Canada

• May 30, 2008

• #1

ok, so I ordered the VFD. I went with the IMO iDrive model 75:
http://www.imopc.com/product_details/71/376/idrive.html

It's a 220v single phase input, 220v three-phase output unit with constant torque characteristics, rated for 1hp (my motor is a 0.75hp Reliance Electric 3-phase made by Baldor)

I also picked up a Siemens General switch to use as a disconnect upstream of the VFD. Went with this unit:

http://www.homedepot.ca/webapp/wcs/stores/servlet/CatalogSearchResultView?D=941184&Ntt=941184&catalogId=11601&langId=-15&storeId=10051&Dx=mode+matchallpartial&Ntx=mode+matchall&recN=112046%204294965510&N=0&Ntk=P_PartNumber

Question is, I've wired LOTS of 110v, but not much 220V. I know I need to use 12 gauge wire, but how many conductors should I buy? is 12/3 ok? Do VFD's generally require 2-live wire (ie: hot, hot, ground) 220v input?

I need some guidance on what to run from the panel, and how to configure the switch - it can be configured 1 or 2 pole, each fusible in the switch.

 

M

minder

Stainless

Joined

Nov 8, 2004

Location

Canada

• May 30, 2008

• #2

Two wire and ground, no neutral required, take the ground to the VFD and then to the motor frame, The disconnect should be double pole fused in both conductors.
M.

 

C

Claven2

Cast Iron

Joined

Apr 28, 2008

Location

Ottawa, Canada

• May 30, 2008

• #3

Great, thanks

I assume since the VFD says it should be fused 15A max, I should be OK with a 15A 2-pole breaker in the panel for the 220?

 

D

DaveKamp

Titanium

Joined

Oct 3, 2004

Location

LeClaire, Ia

• May 31, 2008

• #4

Well...

If it were me, I'd put a pair of 15A fuses in a box on the machine, and use a reasonable breaker in the panel. I think the common 240v single-phase plug is 20A, but could be wrong.

12AWG wire for a 20A circuit is fine... I'm the guy that'll use 10AWG and a 20A plug with a 15A breaker for a 10A machine... and have 10A fuses on the machine. (sigh)

 

Jraef

Titanium

Joined

Aug 10, 2004

Location

San Francisco Bay Area

• May 31, 2008

• #5

90% of VFDs are not rated to be used behind circuit breakers, they are only UL listed for use behind fuses. If the manual does not specifically list a circuit breaker it can be used behind, then there is none.

That's not to say it isn't done all the time, it's just that it is not done legally (as in per code).

Fuses act much faster than circuit breakers and because of that, VFD manufacturers get away with not having to do as much testing if they only UL list them with fuses. But that also means by the way that fuses are a better idea anyway. By the time a breaker clears, a VFD is usually toast, whereas with the right fuses (known as "Semiconductor Fuses"), your VFD might be salvageable after an event.

 

M

minder

Stainless

Joined

Nov 8, 2004

Location

Canada

• May 31, 2008

• #6

Jraef said:

By the time a breaker clears, a VFD is usually toast, whereas with the right fuses (known as "Semiconductor Fuses"), your VFD might be salvageable after an event.

Click to expand...

At ~$20-$200/fuse not many use semi-conductor type, but I would think that they would be ineffective, speed-wise with a large capacitor bank between the fuse and the semi?
M.

 

Last edited: Jun 1, 2008

C

Claven2

Cast Iron

Joined

Apr 28, 2008

Location

Ottawa, Canada

• Jun 1, 2008

• #7

Whatever the case, I canno run power from my panel without using a 220v 2-pole breaker and still meet code. So I will use a breaker in the panel, fuses in the disconnect switch, and then the VFD with analogue input control in the form of a drum switch wired to the VFD - nothing between the VFD and motor. Should work, right?

 

peterh5322

Diamond

Joined

Dec 15, 2002

Location

Monterey Bay, California

• Jun 1, 2008

• #8

The breakers in the panelboard protects the feeder.

The fuses in the fusible safety switch protects the utilization equipment.

You size the beaker to the feeder.

You size the fuses to the utilization equipment.

 

C

Claven2

Cast Iron

Joined

Apr 28, 2008

Location

Ottawa, Canada

• Jun 2, 2008

• #9

Well, the VFD say a max 15A fuse, so that's what I will likely use as it's widely available. My switch is already set up to take plug fuses.

The breaker might well be 15A too then.

 

jim rozen

Diamond

Joined

Feb 26, 2004

Location

peekskill, NY

• Jun 2, 2008

• #10

15 amp breaker in the panelboard, but I would spring for
number 12 wire on general principles.

Jim