# Roto Phase



## randomkiller (Sep 28, 2007)

olectric said:


> We are installing a "roto phase" to get three phase from a 200 amp single phase service. We are installing this for an emergency water pump in a residential community. Do we treat the new 3 phase conductors as service conductors? Do we need a disconnect after the "roto phase" and ground it as service? I think we do but cannot locate a "roto phase" in the code book. Thanks!


 
You need a disconnect but I don't believe you need more than a normal ground from the supplying panel.


----------



## olectric (Dec 11, 2007)

It goes from the Meter socket to a 200 amp 208 volt disconnect to the roto phase to the pump. There is no supply breaker panel. There are no other loads for this application. Just one 30 HP water pump motor. I think I need to treat it as a seperatly derived system after the roto phase..


----------



## randomkiller (Sep 28, 2007)

olectric said:


> It goes from the Meter socket to a 200 amp 208 volt disconnect to the roto phase to the pump. There is no supply breaker panel. There are no other loads for this application. Just one 30 HP water pump motor. I think I need to treat it as a seperatly derived system after the roto phase..


Then yeah, you should handle it just like a regular panel for grounding.


----------



## BryanMD (Dec 31, 2007)

olectric said:


> It goes from the Meter socket *to a 200 amp 208 volt disconnect* to the roto phase to the pump. There is no supply breaker panel. There are no other loads for this application. Just one 30 HP water pump motor. I think I need to treat it as a seperatly derived system after the roto phase..


A FUSED disconnect?


----------



## John (Jan 22, 2007)

olectric said:


> We are installing a "roto phase" to get three phase from a 200 amp single phase service. We are installing this for an emergency water pump in a residential community. Do we treat the new 3 phase conductors as service conductors? Do we need a disconnect after the "roto phase" and ground it as service? I think we do but cannot locate a "roto phase" in the code book. Thanks!


You need to go from the meter socket to the disconnect, then to the phase converter, then to a motor starter and then to the 3 phase motor. It depends on the brand/type of converter that you have because it might have a motor starter built into the converter. Can’t be sure because you didn’t state what you had for converter. I don't think that you need to treat this as a separately derived system, not for just one motor. 
Also check to make sure that the converter is the proper size for the motor. Sometimes you have to upsize the converter for the motor application.


----------



## micromind (Aug 11, 2007)

Article 455 covers phase converters. In skimming over it, it doesn't appear to require any disconnect on the 3 phase side.

I don't see how this could be a separately derived system, as the single phase input carries through and comprises two of the 3 phases on the output. A ground fault on either of the single phase legs would flow directly to the bonding jumper, and a ground fault on the manufactured phase would flow through the converter windings, and also back to the bonding jumper. 

To make this system work automatically, you'll need to provide some means to first start the phase converter, then start the pump. A simple time delay relay in the control circuit would work. A phase converter cannot be started with any load on it. 

Make sure that any single phase loads (control transformers, etc.) are not connected to the manufactured phase.

Rob


----------



## randomkiller (Sep 28, 2007)

micromind said:


> Article 455 covers phase converters. In skimming over it, it doesn't appear to require any disconnect on the 3 phase side.
> 
> I don't see how this could be a separately derived system, as the single phase input carries through and comprises two of the 3 phases on the output. A ground fault on either of the single phase legs would flow directly to the bonding jumper, and a ground fault on the manufactured phase would flow through the converter windings, and also back to the bonding jumper.
> 
> ...


 
Good point.


----------



## Mountain Electrician (Jan 22, 2007)

olectric said:


> We are installing a "roto phase" to get three phase from a 200 amp single phase service. We are installing this for an emergency water pump in a residential community. Do we treat the new 3 phase conductors as service conductors? Do we need a disconnect after the "roto phase" and ground it as service? I think we do but cannot locate a "roto phase" in the code book. Thanks!



Have you considered using a VFD instead of a phase converter? 

http://www.phaseconverterinfo.com/phaseconverter_vfd.htm

I prefer this method as it is an easier, more efficient way to get three phase from a single phase system. You don't have to start a phase converter first, the drive supplies three phase only when needed. The controls are then simpler (no timers needed), and in a water pump application there may be an advantage to being able to program longer acceleration/deceleration ramps to avoid water hammer. You will have to oversize the drive.

Overcurrent protection is provided for the drive and it in turn protects the motor.

In an emergency situation, you probably want as few components in the system as possible and a single phase motor may be better.


----------



## olectric (Dec 11, 2007)

It got a little more copmlicated. Our supply voltage from the power company is single phase 120-/240 volt. The motor is a 480 volt motor. The "add a phase" also has a transformer converting the incoming 240 volt to 480 volt. 

Its a changeorder to a government job (is this relevent?) so we have concluded that we are putting a fused disconnect on the load side of the "add a phase" before the motor starter.


----------



## randomkiller (Sep 28, 2007)

olectric said:


> It got a little more copmlicated. Our supply voltage from the power company is single phase 120-/240 volt. The motor is a 480 volt motor. The "add a phase" also has a transformer converting the incoming 240 volt to 480 volt.
> 
> Its a changeorder to a government job (is this relevent?) so we have concluded that we are putting a fused disconnect on the load side of the "add a phase" before the motor starter.


 
IMO I would say that a fused disconnect before the roto phase would protect the "add a phase" and the overloads in the starter will take care of the motor protection. How far is it from the "add a phase" to the motor starter. are they with in sight of each other?


----------



## olectric (Dec 11, 2007)

We will have a 250 volt circuit breaker feeding the "add a phase/transformer". It is all in close proximity so yes, it is within sight. The motor is actually a submerged pump in a giant underground water tank. I am concerned about protecting the wiring from the "add a phase" to the starter so we have decided to put the disconnect in anyway.


----------



## randomkiller (Sep 28, 2007)

olectric said:


> We will have a 250 volt circuit breaker feeding the "add a phase/transformer". It is all in close proximity so yes, it is within sight. The motor is actually a submerged pump in a giant underground water tank. I am concerned about protecting the wiring from the "add a phase" to the starter so we have decided to put the disconnect in anyway.


Oh I see. How much wire is in between the two?


----------

