Motors and Variable Frequency Drives

1 hp Single Phase Motor

There are many options and recommendations for which motors and VFDs to use on a 2×72 belt grinder. Below is a simplified set of recommended options for the Nexus Grinders. These are by no means the only options — do your research and become informed on what is needed to power and control a 2×72 belt grinder.

The key factor in determining the size of motor and/or VFD is the power you have available in your shop or garage:

  • 115 volt supply — look at 1.0 to 1.5 horsepower motors.
  • 230 volt supply — look at 1.0, 1.5 and 2.0 horsepower motors. You can go larger, but you will need a higher-rated VFD, which increases cost.

Motors

A 56C frame motor with a foot mount lets you use the C-face mount for the NG-3, and the foot mount works for the NG-2 as well. Most motors today offer both a C-face and a foot mount — if yours doesn’t, make sure you obtain the correct motor mount for the grinder. Nexus Grinders sells motors for the NG-3 and NG-2.

  • Use a Totally Enclosed Fan Cooled (TEFC) motor. Open motors are a poor choice — grinding dust gets inside and the motor eventually fails.
  • If you are using a 4″ or 5″ drive wheel, you want a 3600 RPM motor.
  • Look for motors that are electronically reversible.
  • If you are using a VFD, you need a 3-phase motor (see the VFD notes below).
  • For a counter-shaft setup with pillow blocks, sheaves and belt, you can use a 1.5 or 2.0 hp single-phase motor — this setup works only with the NG-2 models.

Variable Frequency Drives (VFDs)

  • If you want to use a VFD, you must use a 3-phase motor.
  • VFDs convert single-phase 115 or 230 volt input into 3-phase output to the motor.
  • You can’t use a single-phase motor on the industry-standard VFDs that most knife makers use.
  • VFDs control speed, and some also allow forward and reverse settings.
  • You can’t use a motor rated higher than the VFD. You can use a higher-rated VFD with a lower-rated motor — e.g. a 2.0 hp VFD with a 1.0 to 2.0 hp 3-phase motor. Do not use a 3.0 hp motor with a 2.0 hp VFD.
  • Look for a NEMA 4-X protection rating — sealed against dust and water with a corrosion-resistant exterior. A NEMA 1 drive needs added protection, a fan and a filter. NEMA 4-X is not much more money and well worth it.

KB Electronics sells many VFD models. You can buy KBAC drives from Nexus Grinders in Canada, an authorized distributor.

  • KBAC-27D — works on 115 and 230 volt input with 1.0, 1.5 and 2.0 hp 3-phase motors. On 115 volt input: up to 1.5 hp motor, 22 amps max, 25 amp breaker. On 230 volt input: up to 2.0 hp motor, 16.7 amps max, 20 amp breaker.
  • KBAC-24D — limited to a maximum 1.0 hp 3-phase motor. On 115 volt input: 14.4 amps max, 20 amp breaker.

The KBAC VFDs are rated NEMA 4-X. You can also add an optional forward/reverse switch and a line switch to turn power off to the drive. See Table 2 on page 7 of the KBAC manual.

Our recommended setups

Option 1 — 1.5 or 2.0 hp, 230 volt, 3-phase

  • 1.5 or 2.0 hp, 230 volt, 3-phase motor
  • 56C or 56HC flange mount, electronically reversible, TEFC
  • 3600 RPM (use with a 4″ or 5″ drive wheel)
  • KBAC-27D VFD, 230 volt single-phase input (rated up to 2 hp)

Option 2 — 1.0 to 1.5 hp, 230 volt, 3-phase

  • 1.0 to 1.5 hp, 230 volt, 3-phase motor
  • 56C or 56HC flange mount, electronically reversible, TEFC
  • 3600 RPM (use with a 4″ or 5″ drive wheel)
  • KBAC-27D VFD, 115 volt single-phase input (rated up to 1.5 hp)

Option 3 — 1.0 hp, 230 volt, 3-phase

  • 1.0 hp, 230 volt, 3-phase motor
  • 56C or 56HC flange mount, electronically reversible, TEFC
  • 3600 RPM (use with a 4″ or 5″ drive wheel)
  • KBAC-24D VFD, 115 volt single-phase input (rated up to 1 hp)

Option 4 — 1.5 hp, 115 volt, single-phase

  • 1.5 hp, 115 volt, single-phase motor
  • 56C or 56HC flange mount, electronically reversible, TEFC
  • 3600 RPM (use with a 4″ or 5″ drive wheel)
  • Counter-shaft with pulleys and belt, or a direct motor mount on the NG-3

Nexus Grinders sells 1 hp, 1.5 hp and 2 hp three-phase motors, as well as single-phase motors in 1 hp, 1.5 hp and 2 hp. For KBAC drives, review the manual at KB Electronics or contact Nexus Grinders — an authorized KB Electronics re-seller — at kbelectronics.com.

Shop motors & VFDs

Shop grinder motors →

Frequently asked questions

Do I need a 3-phase motor to use a VFD?

Yes. The industry-standard VFDs knife makers use — such as the KBAC series — take single-phase 115 or 230 volt input and output 3-phase power, so they require a 3-phase motor. You cannot run a single-phase motor on one.

KBAC-24D or KBAC-27D — which VFD do I need?

The KBAC-24D is limited to a 1.0 hp 3-phase motor. The KBAC-27D handles 1.0, 1.5 and 2.0 hp 3-phase motors on 115 or 230 volt input, so it is the more flexible choice — most makers running 1.5 or 2 hp choose the 27D.

Why a TEFC motor instead of an open motor?

Grinding produces fine, abrasive dust. A Totally Enclosed Fan Cooled (TEFC) motor keeps that dust out of the windings and bearings. An open motor lets dust in and will eventually fail.

What NEMA rating should the VFD have?

Look for NEMA 4-X — a sealed, corrosion-resistant, washdown/watertight enclosure that keeps grinding dust and moisture out. A NEMA 1 drive needs an added fan, filter and enclosure to survive a grinding shop. The KBAC drives are NEMA 4-X.

Working on electrical circuits or incorrectly connecting equipment can be extremely hazardous. Consult a qualified electrician if you are unsure how to make safe connections. Electrical work should meet or exceed national, provincial and local codes, and you may need a permit for panel changes. Check with your local authorities before starting.

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