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380 volt 50KW induction heater that won't turn on

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Electricalguy

Member
Location
Pennsylvania
Occupation
Electrician
I am working on trying to get an new induction heater to turn on. I have a 480 volt 60 amp 3 phase feed coming from my main breaker box. My 60 amp 3 phase breaker is then going a disconnect since my breaker box is not line of site. The 480 disconnect is powering a step down delta transformer 480 volt to 380 volt and has no neutral or ground terminal on transformer just chassis ground. We ran power wires from the 380 lugs and a wire from chassis ground to the induction heater inlet power terminal on the unit. There is a ground stud on the chassis of the induction heater but we did not hook up a ground to this terminal. it seems there is no connection from the ground coming in to the unit to this ground stud. When I meter from phase to phase I get 380 from a to b, a to c and b to c. When I go from metal reference on the chassis I got 150 on phase a 201 on b and 280 on c terminal. The machine is looking for a 220 volt lead from terminal a on the supply. With only 150 volts on a terminal it won't power up. If I were to run a ground from the chassis/breaker box to the ground terminal of the induction heater that would also be common to the transformer would this level out my power on all three terminals to 220 and turn the induction heater on? If the chassis had to be grounded to eliminate any potential charge why would they not just tie in the ground from the supply source or should this be separate ground like to rods outside or such? The building is cinder block so there is no structural steel to tie to. Any thoughts?
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Appears you may have needed a 380/220 Wye Secondary Transformer rather than a Delta secondary
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
3 phase Transformer output can be Delta (3 wire) or Wye (4 wire). A 4 wire Wye transformer would have a "neutral" point measuring 220 phase to ground(neural) just as a common USA 208Y/120 has.
Appears someone purchase the wrong transformer for your application.
 
E

Electricalguy

Member
Location
Pennsylvania
Occupation
Electrician
augie47 said:
3 phase Transformer output can be Delta (3 wire) or Wye (4 wire). A 4 wire Wye transformer would have a "neutral" point measuring 220 phase to ground(neural) just as a common USA 208Y/120 has.
Appears someone purchase the wrong transformer for your application.
Click to expand...
So it would be better to buy a "wye" and tie a neutral and a ground together at the transformer then run 4 wires over to the device being a phase A, B and C then tie the neutral in to the power terminals on the 4th terminal and then bond using a ground wire tying to the ground terminals on the induction machine and the heater? So the Delta will never work for this? Im just trying to get info before I go back to the shop where this customers unit is.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
If you wish to pursue it there are other ways you might "rig" it to get by such as the one Larry suggested in post #10 or obtaining control voltage from an existing 220v source in the plant but I hesitated to go there as machine warranty questions might arise.
What you state above is correct but note you also need to address 250.30 concerning grounding a SDS,
 
E

Electricalguy

Member
Location
Pennsylvania
Occupation
Electrician
augie47 said:
If you wish to pursue it there are other ways you might "rig" it to get by such as the one Larry suggested in post #10 or obtaining control voltage from an existing 220v source in the plant but I hesitated to go there as machine warranty questions might arise.
What you state above is correct but note you also need to address 250.30 concerning grounding a SDS,
Click to expand...
250.30 in 2020 NEC? or what year?
 
dkidd

dkidd

Senior Member
Location
here
Occupation
PE
How are you grounding the secondary delta? Or do you have ground alarms.

You could look at a zig-zag transformer to derive a neutral and ground it.
 
E

Electricalguy

Member
Location
Pennsylvania
Occupation
Electrician
augie47 said:
If you wish to pursue it there are other ways you might "rig" it to get by such as the one Larry suggested in post #10 or obtaining control voltage from an existing 220v source in the plant but I hesitated to go there as machine warranty questions might arise.
What you state above is correct but note you also need to address 250.30 concerning grounding a SDS,
Click to expand...
In no way would I rig anything. If its not correct I don't work on it.
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
here is a fairly typical 3 phase delta to wye xfmr. you would bring in 480 3 phase to the primary. The secondary would give you whatever volts you order when you buy the transformer. Normally you would bond X0 and the ground stud together in the transformer and bring in your grounding electrode system connection to the same point. You can connect them downstream if you chose but can only be bonded together in one spot. X1, X2, and X3 would go to some kind of overcurrent device like a set of fuses or a CB. you would need to bring the neutral (from X0) and the equipment grounding conductor (EGC) from the xfmr ground stud as well since they all have to travel together.
1626711201130.png
In the case of a 480 primary to 380 Wye secondary, you would have 380 V line to line on the secondary, and 220 V from any line to neutral. This is the most common European system.
 
E

Electricalguy

Member
Location
Pennsylvania
Occupation
Electrician
petersonra said:
here is a fairly typical 3 phase delta to wye xfmr. you would bring in 480 3 phase to the primary. The secondary would give you whatever volts you order when you buy the transformer. Normally you would bond X0 and the ground stud together in the transformer and bring in your grounding electrode system connection to the same point. You can connect them downstream if you chose but can only be bonded together in one spot. X1, X2, and X3 would go to some kind of overcurrent device like a set of fuses or a CB. you would need to bring the neutral (from X0) and the equipment grounding conductor (EGC) from the xfmr ground stud as well since they all have to travel together.
View attachment 2557242
In the case of a 480 primary to 380 Wye secondary, you would have 380 V line to line on the secondary, and 220 V from any line to neutral. This is the most common European system.
Click to expand...
Currently the customer has a 480 volt with ground coming from a disconnect to a 3 tap 480 in and bond the trans chassis and 3 tap 380 out with just chassis bond. The customer tied the 6-3 nm-b in to the trans. he tied white black and red to the 3 380 out taps and the ground to the chassis ground/bond. the ground/chassis bond comes from the breaker box at the main service panel which is a few hundred feet away and then through the disconnect to the trans in the customers shop. he needs 380 p-p and 220 p-g. his p-g is bellow and above 220 depending what leg you meter. the ground is attached at the incoming power point at the machine but not connected to the bond screw on the chassis. the unit has a reference wire attached at the A phase leg and is only reading 150 volts not the 220 from phase to ground. Customer told me today he bought a delta transformer for his induction heater because someone told him it would work with it. I would have thought a "wye would have been better for this application. with the voltages floating all over the place I don't think with this current set up he will ever get this unit working..... I suggested him to make sure all the bond/grounds were common on the power coming in and the chassis bond and he said that did not fix the power issues going from p-g on any of the 3 legs. He just bought the trans and the induction heater and is sounds like he bought the wrong trans but I am trying to get it to work with out buying a ton of extra parts or doing any type of quick fix that may be dangerous. ???
 
Z

zbang

Senior Member
Location
Roughly 5346 miles from Earls Court
The customer bought the wrong transformer, seems to happen a lot. (I wonder who that "someone" was, probably not anyone in the electric trades.)
If the equipment really needs a wye connect feed and isn't convertible for delta, nothing else will do. Seems like the choices are either a zigzag transformer to establish a neutral point or sell the delta/delta and replace with a delta/wye.
 
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