Is this a DC motor and opinions on KB VFD?

S

SRR805

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Here's the dataplate on my new to me millrite. What's throwing me off is the "DC". Not sure if that's an internal code from GE or if that means that's a DC 3-ph motor. The place I bought the mill from had it running on 220v 3ph but the salesman didn't know if it was dc or ac power.
Dataplate millrite.jpgOther question is what are people's experience with KB vfd's? I'm not rich but it is a business expense so reliability and ease of use is more important than cost.
 
I don’t think it’s dc because the plate says 60 cycles. That is the difference between ac and dc. Also says 3 ph, (another sign of ac current)

Chuck
 
motor basics, DC motors do not have a frequency like alternating current motors... the hertz listed is the frequency at which current alternates. So no, the illustrated motor is not a DC motor.
 
Jubil said:
I don’t think it’s dc because the plate says 60 cycles. That is the difference between ac and dc. Also says 3 ph, (another sign of ac current)

Chuck
Click to expand...
You beat me by half a second.
I blame my arthritis
 
Looks like the motor plate on my Bridgeport. The "DC" is in the "NO" field, which makes me think it's a part number or something. Dumb thing to use when there are so many other options, but whatever I guess. With Phase, Cycles and voltages matching up with a 3 phase standards, I would go with it being a 3 phase AC motor. There isn't really a 3 phase DC. Phase refers to how the waves relate to each other. DC has no waves. :)

The KB VFDs seem good. I've never heard of people having problems with them. I went with cheapo imports from ebay and haven't had any trouble, but I also take care to keep the chips out of them. The better units are sealed and that is a non-issue. But they also cost 4x as much, so I figured I could take a shot and replace it if I burn it up.
 
Well - it does have the letters "DC" on it, but there are some things else to indicate that it is actually a 3-phase AC induction motor that expects to see 60 Hz mains frequency. Mainly, it actually states it is 3-phase.

Even while I was typing, @Jubil and @TorontoBuilder got there first. :)
Expect to see six terminal posts with links that allow it to be wired into STAR or DELTA configuration, and no capacitors nor brushes.

The 440V is the reference to the line-to-line 3-phase voltage. The line-to-neutral voltage, accessible in star (aka WYE) connection would be 440V ÷ √3 = 254V. That could be the highest voltage the "Tri-Clad" insulation was specified for, and in many parts of the worlds, was actually used.

208 is the very common standard phase voltage for places where the 3-phase line voltage is 360V
220 is another very common value, corresponding to the European supplies that use 380V 3-phase .
In the UK, we get to 235V, corresponding to 415V 3-phase
The line voltage is always √3 x phase voltage.

The motor is a pretty universal GE 5K series 3-phase induction motor, and it won't much care what supply you use. You could even feed it from a VFD.

[Edit: From a VFD, if the input to the electronics is single phase, then the bus voltage would be lower. To get the full power out, you might use the DELTA connection, but here, you very definitely have to read the VFD instructions carefully! ]
 
Last edited:
graham-xrf said:
Well - it does have the letters "DC" on it, but there are some things else to indicate that it is actually a 3-phase AC induction motor that expects to see 60 Hz mains frequency. Mainly, it actually states it is 3-phase.

Even while I was typing, @Jubil and @TorontoBuilder got there first. :)
Expect to see six terminal posts with links that allow it to be wired into STAR or DELTA configuration, and no capacitors nor brushes.

The 440V is the reference to the line-to-line 3-phase voltage. The line-to-neutral voltage, accessible in star (aka WYE) connection would be √3 x 440VAC = 254V. That could be the highest voltage the "Tri-Clad" insulation was specified for, and in many parts of the worlds, was actually used.

208 is the very common standard phase voltage for places where the 3-phase line voltage is 360V
220 is another very common value, corresponding to the European supplies that use 380V 3-phase .
In the UK, we get to 235V, corresponding to 415V 3-phase
The line voltage is always √3 x phase voltage.

The motor is a pretty universal GE 5K series 3-phase induction motor, and it won't much care what supply you use. You could even feed it from a VFD.
Click to expand...
@graham-xrf your arthritis must be worse than mine :grin:
 
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