Rotary phase converter question

S

SFisher

Member
Location
Virginia
Occupation
retired electician
My neighbor is building a slaughter house. Some of the equipment he has purchased is only available in 3phase so he is buying a rotary phase converter. Three phase is not available here. The rpc puts out 240 volts 3 phase. All of his equipment is rated (200v - 230v) except one. His grinder is 7.5 hp rated at 200v. The Hobart 4346 grinder is made in 200v, 230v and 460v, leads me to believe running the 200v grinder off the rpc 240v is not a good idea. American rotary wants to sell him a transformer for the entire system. I was wondering if anyone in the know would think using a separate VFD or digital phase converter for the grinder would be a solution. or maybe the grinder would run fine off the rpc despite the 200 v rating?
 
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E

Eddie702

Licensed Electrician
Location
Western Massachusetts
Occupation
Electrician
If the motor is rated 208v and is suitable for use on 240 it should say so on the name plate. However 208 equipment on a 240v converter may not be a good idea.
 
S

SFisher

Member
Location
Virginia
Occupation
retired electician
MTW said:
Have him buy the grinder with the 230v stator winding. The 200V model is a European 200/346V 50Hz model.

Check the parts list here.

A 50Hz motor will turn 20% faster on 60Hz and likely cause it to overload, when running it at full capacity.
Click to expand...
He already has the grinder. It is 60 Hz. If available, which we haven't found yet, the motor is almost as much as he paid for the grinder. I understand that a VFD can act as a phase converter and match the needed voltage economically. I have no experience with VFDs.
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
SFisher said:
He already has the grinder. It is 60 Hz. If available, which we haven't found yet, the motor is almost as much as he paid for the grinder. I understand that a VFD can act as a phase converter and match the needed voltage economically. I have no experience with VFDs.
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An electronic phase converter would potentially do the same thing a lot more cheaply than a VFD, unless economies of scale in VFD production and sales are enormous.
 
M

MTW

Senior Member
Location
SE Michigan
Can you post the machine tag with the rating and the ML# ? Finding a VFD to convert from1 phase into 3 phase @ 7.5 HP 240V will be like finding hens teeth, unless you use a way oversized 3 phase model, which is big money.

A small pair of 1 phase buck/boost transformers for just the grinder would be more economical fed from the RPC. RPC voltage outputs can be higher than the input line voltage when lightly loaded.

Do you know what the line voltage measures at the site now? What size RPC is planning on? And what are the other equipment loads going to be, connected to the RPC?
 
S

SFisher

Member
Location
Virginia
Occupation
retired electician
MTW said:
Can you post the machine tag with the rating and the ML# ? Finding a VFD to convert from1 phase into 3 phase @ 7.5 HP 240V will be like finding hens teeth, unless you use a way oversized 3 phase model, which is big money.

A small pair of 1 phase buck/boost transformers for just the grinder would be more economical fed from the RPC. RPC voltage outputs can be higher than the input line voltage when lightly loaded.

Do you know what the line voltage measures at the site now? What size RPC is planning on? And what are the other equipment loads going to be, connected to the RPC?
Click to expand...
This is what I was wondering. I can post the answers here after awhile. Thanks
 
S

SFisher

Member
Location
Virginia
Occupation
retired electician
MTW said:
Can you post the machine tag with the rating and the ML# ? Finding a VFD to convert from1 phase into 3 phase @ 7.5 HP 240V will be like finding hens teeth, unless you use a way oversized 3 phase model, which is big money.

A small pair of 1 phase buck/boost transformers for just the grinder would be more economical fed from the RPC. RPC voltage outputs can be higher than the input line voltage when lightly loaded.

Do you know what the line voltage measures at the site now? What size RPC is planning on? And what are the other equipment loads going to be, connected to the RPC?
Click to expand...
He is planning on buying a 20HP RPC. He has the 7.5 hp grinder plus Vacuum packer 4.5hp, stuffer 1.5hp, saw 3hp. Most of which won't run at the same time (he says). Voltage at the building is 120/240 right on the money. The tag on the machine says volts 200, amps 22, ML# 19634-4, 7.5 hp. Model 4346 Hobart. Thanks for the help.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
MTW said:
The 200V model is a European 200/346V 50Hz model.
Click to expand...
The only place that uses 200V 50Hz is Japan, not Europe. 346V 50Hz is not used anywhere. But since we now know it is a 200V 60Hz grinder, that’s a moot point.

200V 60Hz motors are designed for use on 208V systems. Unlike “tri-rated” (208-230/460V) motors, those that actually say 200V on the nameplate will not like 240V, especially 340V from an RPC that will undoubtedly be unbalanced. So yes, since you are uncomfortable with the idea of using a VFD, I too suggest bucking that down closer 200V on that machine.
 
Besoeker3

Besoeker3

Senior Member
Location
UK
Occupation
Retired Electrical Engineer
Jraef said:
The only place that uses 200V 50Hz is Japan, not Europe. 346V 50Hz is not used anywhere. But since we now know it is a 200V 60Hz grinder, that’s a moot point.
Click to expand...
Spot, on Mr Jraef. That said e do use a fair bit of DC for variable speed drives.
 
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norcal

Senior Member
200V replaced 208V as the rated voltage on motors, although I have a couple of 1974 Rockwell machines that were supplied with 200V 3Ø motors, a 7" grinder, & a HD wood shaper, they were both former educational machines, both are running with VFD's since only 240V 1Ø is available & in the case of the grinder without that motor there is no tool, plus for motors 3 HP & under the VFD's were reasonable, the grinder is 1/2 HP, & the shaper is 2 HP, although that motor could be changed, but not for the $200 the VFD cost.
 
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