Emerson Control Techniques Focus 3N, User Manual, Page: 11 / 82

Page 5
Motor Compatibility
The Focus 3 was designed to run standard 90 Vdc or 180 Vdc Shunt Wound or Permanent
Magnet DC motors in one direction. The Focus 3 can run motors with other characteristics
(such as Universal motors) but one must review those requirements to insure compatibility.
Universal motors have commutator brushes but typically plug into the AC power line. Universal
motors are often used in tools such as Drills, Saws, Shop VAC’s, Routers, etc and typically
cannot be run in reverse.
Shunt Wound Motors that are controlled by single phase DC drives typically have 4 power
wires. Two of these are the Armature leads typically designated A1 & A2 or A+ & A-. The
other two power wires are the shunt field leads and typically designated F1 & F2 or F+ & F-.
The Focus 3 can supply up to 1 Amp for shunt field excitation (field current requirements
beyond 1A may damage field rectifier diodes). If your motor does not have Field Current
information on the nameplate, you can determine compatibility by measuring your motors Field
resistance using a calibrated ohmmeter.
Motors with:
90v Armatures typically require 100 Vdc for field excitation. In these cases, the Focus
3 requires 120vac input power and must be internally set for this input level. The motor
Field resistance should not be less than 100 ohms when cold.
180v Armatures typically require 200 Vdc for field excitation. In these cases, the Focus
3 requires 240vac input power and must be internally set for this input level. The motor
Field resistance should not be less than 200ohms when cold.
240v Armatures typically require 150 Vdc for field excitation. In these cases, the Focus
3 requires 240vac input power and must be internally set for this input level. The motor
field resistance should not be less than 150 ohms when cold and will require a series
resistor to drop the additional field supply voltage. Consult Control Techniques Technical
Support for additional information.
Motors with:
Permanent Magnet Motors typically have only 2 power wires. These are the Armature
leads and typically designated A1 and A2 or A+ and A-.