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PM 935tv what phase converter needed?

Discussion in 'PRECISION-MATTHEWS' started by Sdmf5150, Mar 18, 2017.

  1. Sdmf5150

    Sdmf5150 United States Iron Registered Member

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    Hey guys! New to the forum. I will be getting a 935tv and was wondering if it would be better to go with a rotary phase converter over a standard one. Thanks
     
  2. davidpbest

    davidpbest Active Member Active Member

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    Depends on what you mean by "standard one". I don't understand your question. Are you asking whether 3-phase with a rotary converter is better than single phase? Or whether a rotary converter is better than a digital converter like a Phase Perfect?
     
  3. Sdmf5150

    Sdmf5150 United States Iron Registered Member

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    I was wondering if a rotary converter worked differently than a static non rotary converter.
     
  4. davidpbest

    davidpbest Active Member Active Member

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    OK, here is a short tutorial on the three types of equipment that are commonly used to convert single-phase to three-phase power:

    Rotary Phase Converter: In the simplest terms, a rotary phase converter is really a 3-phase motor, which has three windings on the armature and three field coils, but only two of the windings are energized by the incoming 2-phase power (230VAC has two “hot” legs out of phase, is called "single phase”, but for this purpose, think of it as 2-phase). The third winding on the rotating armature produces the 3rd leg (phase) when rotating, much in the same way a generator produces electrical current. Think of a rotary phase converter as a single phase motor driving a generator that produces the 3rd “hot leg” that’s missing from the power company supply, and required to run 3-phase equipment. A Rotary Phase Converter can be used to supply power to multiple machines in a shop environment, but it’s often difficult to stabilize the manufactured 3rd hot leg, and that leg’s voltage can spike wildly when large loads (motors) are started. Popular suppliers of Rotary Converters in the USA are American Rotary and Kay Industries, but there are many suppliers and users sometimes build their own using a 3-phase motor as the basis for their implementation. A Rotary Converter can be connected directly (with proper disconnects and protection) to the driven machines, or run through a 3-phase load center (breaker panel).

    Solid State Phase Converter: This is completely different beast. It takes the incoming power, converts it to DC, then from that DC it re-generates AC but phased as the 3rd leg. Phase Perfect is the most widely used manufacturer of solid state phase converters in the USA. They are typically 2-3 times the price of a similarly sized rotary phase converter, but are voltage stabilized and ideal in situations where there’s a combination of different sized motors in the attached equipment, as well as computerized logic circuitry. Many suppliers of CNC equipment require the use of a Solid State Phase Converter if 3-phase is not available from the power source. In contrast to a rotary phase converter which has a motor turning, making noise and heat and consuming electricity even when not in demand, the Phase Perfect is a solid state device that doesn’t draw power until you start the equipment connected to it. A Solid State Phase Converter can also be used to power multiple machines in a shop environment, and can be connected directly (with proper disconnects and protection) to the driven machines, or run through a 3-phase load center (breaker panel).

    Variable Frequency Drive (VFD): A VFD is similar to a solid state phase converter, but designed to provide power to a single device directly attached to the VFD (like a single motor). VFD’s can not generally be used to power multiple machines, but are programmable to alter the characteristics of the output voltage (all three phases) to vary the frequency (hence speed of the attached motor), or drive a motor with certain current levels to improve torque at lower RPM’s. VFD’s are available that are powered by single- or 3-phase power. VFD’s are typically installed in or adjacent to the equipment with the motor being controlled, often in a separate NEMA enclosure.

    All three types of converters mentioned above are available in various sizes/capacities, and are typically matched to the size of the maximum load (horsepower or Kw) of the system they are supplying.
     
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  5. mksj

    mksj Active User H-M Supporter-Premium

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    Standard static converters that use capacitors to generate the third leg, thus no moving parts. With a RPC the a 3 phase motor is used to generate the third leg along with capacitors, you are using the induction of the motor coils to provide additional regenerative power for the 3rd leg. Static converts are used in light duty small motor applications, and you usually loose about 50% of the operating motor Hp, they also need to be more closely matched to the specific motor Hp. A RPC usually is about 90% efficient. Electronic generation of three phase via a solid state phase converter or VFD, allow up output more than the motor rating for short periods. Since you are looking at the 935TV (belted variable speed), then ad RPC would probably be the optimal power source for converting single phase to 3 phase. On the 935TS (fixed pulley speeds), a VFD would probably be the preferable choice. In most cases you would operate the VFD in something like a 30-90Hz range.
     
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  6. Sdmf5150

    Sdmf5150 United States Iron Registered Member

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    Thanks guys. I think I'm going to go with the rotary converter. That way I can
    Get the full potential of the motor
     
  7. qualitymachinetools

    qualitymachinetools United States Active User H-M Supporter-Premium

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    Either that, or just order the machine in single phase, it is a lot cheaper than a rotary converter, and less messing around to get it up and running!
     
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  8. MonkMan

    MonkMan United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Welcome SD. be sure the send pictures when you get setup.
     
  9. Sdmf5150

    Sdmf5150 United States Iron Registered Member

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    I will definitely do that! Thanks for the info!
     
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