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Wiring PM 1340GT with Hitachi VFD, 30amp ??

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LarryAZ

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#1
Hello,
The factory reference guide (page 10) for the Hitachi VFD WJ200-015SF specifies 10AWG wiring and a 30amp fuse for the single phase 240v power source. As I'm only running a 2HP 220v, 3 phase motor (PM 1340GT lathe) would 12awg wire and a 20amp fuse work and also be safe ?

The reason for asking is that my garage is already wired with 240v (20amp fuse) 12awg wire. Also found VFD cable manufactures online specify the smaller wire for that size motor. As a last resort I'll run new wiring to the garage if required.

Thank you,
Larry
 

Karl_T

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#2
No way will a 2hp motor draw 20 amp. You will be fine with 12 wire and 20 amp fuse.
 

LarryAZ

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#3
I understand the motor will not draw 20 amps.
But will the VFD draw a lot of amps when it converts the single phase power to three phase ? The side of the VFD says input of 50HZ/60Hz, 200-240V 1PH 20.2/16.8 A. Maybe Hitachi lists this for worst case industrial applications ? If I understand NEC says wiring needs to be rated at 125% of power inverters max input requirements ??????

Thanks.
 

JimDawson

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#4
Unless you are operating the motor at maximum load continuously, you should be OK. VFDs are pretty efficient so the input power is a direct function of the load. The inrush current is huge but only lasts for a fraction of a second when you power up the VFD, not enough time for the wiring to heat up.

NEC requirements are pretty conservative, and assume continuous full load operation with occasional overload. If your entire garage is fed from one 20 amp circuit, then maybe it's time to add another circuit or heavier wiring.
 

mksj

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#5
The 2 hp motor is 3 phase, and is around 5-6 amps at 240VAC, the inverter output current based on the parameters can draw up to 180% for up to a minute. The rated input wiring of the VFD is dictated not by VFD output, but the VFD rating input and also takes into account short turn maximum loads. The breaker protects the wiring, a 30A breaker is typically used for 12 AWG wire, a larger breaker with the same gauge wire may be used for motor loads beacuse of the higher starting current. If you have longer wiring distance, then you will get less voltage drop with a heavier gauge wire. Depending on the VFD manufacturer the wiring recommendations probably reflect worse case scenario's and maximum continuous loads.

Suffice it to say, I ran my 1340GT with a WJ200 and an inverter motor set to 180% overload for years with 12AWG wire and a 20A breaker with no problems. You will be fine with that and the wire will be protected by the breaker.
 

LarryAZ

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#6
To clarify about the garage wiring. It also has separate 120v 15amp breakers for regular lighting and plug ins. The 240v 20amp breaker does not supply power to the 120v 15amp circuit.

Sounds like I'm good to go with this lathe project.

Thanks,
Larry
 

Cadillac

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#7
When I installed my vfds I had the same kind of questions. My vfd manual wants a 20a fast acting fuse. I ended up sourcing it because thats what the manual said. I had the same question you have your motor amperage but how much is the vfd pulling?? The gauge of wiring I think you’d be okay with 12g. I used 10 from my motor to vfd because I had to order it anyway being shielded. Only 2’ from McMaster Carr along with the fuses.
I wouldn’t worry about what wire is in the walls. 12g is pretty standard and should work fine. As long as your not running the lathe of a 100’ cord.
 

machPete99

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#8
I have the (similar) Hitachi WJ200-022SF on my 2HP Clausing lathe, on double 20A 240V circuit, 12 gauge wiring. I have not seen any issues, and never popped the circuit breaker so is pulling less than the 20A per side. For longer runs it might be a good idea to go up in the wire gauge.
 

LarryAZ

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#10
Thank you Pacifica, I'll look into it.
 
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