More Information

Frame size families:

Frame 3.25 (R30 Series)

Frame 4.25 (R40 Series)

Frame 5.75 (R60 Series)

Frame 7.5 (R80 Series)

Motor Features:

Brushless Servo Motors

Empire Magnetics' PT Series Brushless Servo Motors are sealed and equipped with air fittings for pressurization.  With an optional temperature sensor, PT motors can be easily designed into a system that meets NFPA requirements for Class I, Class II and Class III hazardous locations.  In a typical installation - such as spray painting, printing, flour mills, fuel processing, alcohol production, chemical processing or rocket fuel machining - the motor is remotely located in a hazardous area.  Air lines, and power and temperature sensor cables, run to the control station in a non-hazardous area.  Protective conduit shields cabling from mechanical damage.  At the control station, a temperature indicator with a setpoint alarm displays motor temperature.  The setpoint alarm output will cut power to the drive if the temperature exceeds the setpoint.  A differential pressure switch on the return air line monitors motor pressure.  If pressure fails, this switch also cuts power to the drive.  When power is applied, the motor undergoes a purge delay period before being energized.

Safety Regulations

National Fire Protection Association regulation number 496 describes how pressurized electrical equipment may be safely deployed in a hazardous environment. The regulation, "Standard for Purged and Pressurized Enclosures for Electrical Equipment in Hazardous (Classified) Locations  NFPA 496-1982" may be obtained from the NFPA:

The National Fire Protection Association
Batterymarch Park, Quincy, MA 02269
1-800-344-3555 or 617-770-3000

Installation

Motor system installation must be performed by qualified electricians in compliance with the National Electrical Code and the relevant provisions of the NFPA-496 regulation.  A copy of the regulation must be obtained prior to installation to verify compliance.   The NFPA-496 regulation has three basic requirements which must be met to deploy a PT brushless motor in a hazardous environment. These are described briefly below and illustrated with a block diagram of motor system components.  THIS DOCUMENT IS AN INCOMPLETE GUIDELINE, AND MUST NOT SERVE AS A SUBSTITUTE FOR OFFICIAL REGULATIONS.

Pressurization

The motor must be pressurized with insert gas or air that is free of combustibles.  A pressure of 1 to 5 PSI is adequate to meet the requirement.  The recommended configuration for Division 1 installation is to route all motor cabling in conduit directly into the motor. Motors have 1/4, 3/8,  or 1/2 NPT cable entry holes to facilitate conduit connection. The conduit may be incorporated as part of the pressurized system. Non-combustible materials must be used. The regulation requires that power to the motor be shut off if the pressure fails.  This necessitates incorporation of a pressure switch in the system, connected so as to cut power to the drive when pressure is lost.  If the pressure switch is located in the hazardous area, either the electrical circuit which includes the switch must be rated either Intrinsically Safe or Explosion Proof.

Purging

The motor must be purged.  The regulation requires that inert gas or air that is free of combustibles be passed through the motor to displace any combustible gasses before power is applied.  This implies that an exhaust valve or orifice is needed.  Empire Magnetics provides a 10-32 threaded aperture to connect the required air lines. The motor is to be purged with a volume of gas equivalent to ten times the internal volume of the motor.  This may be accomplished using an "on delay" type of time delay relay.  When pressure is first applied, the above pressure switch provides power to the time delay relay.  The relay waits a fixed period before passing power through to the motor drive.  This same device may be used to operate an electrically controlled valve to halt
purging after the required period.

Temperature monitoring

The motor's temperature must not exceed 80% of the autoignition temperature of whatever combustible material is present.  A temperature monitoring system must be installed which automatically shuts off power to the motor if it gets too hot. Empire Magnetics provides optional temperature sensors for monitoring motor temperature.  These can be combined with a compatible temperature controller to achieve the required shut off.  External temperature sensors may be used as long as they have an appropriate rating for the hazardous location.

Required Equipment

A compressor or compressed air tank with a low pressure regulator is required. Nitrogen, helium or other inert gases may be used.  In humid climates, a dryer is recommended to prevent corrosion inside the motor. Pressure regulators and dryers may be found in general equipment catalogs such as the McMaster-Carr catalog.
Motors with temperature sensors require a setpoint temperature controller. Empire Magnetics' RTD sensors are 100W at 0ºC (a = .00385 European).  They are compatible with model 50 controllers from Omega Engineering, among others. A suitable differential pressure switch is also available from Omega Engineering.  Time delay relays are available from most major relay manufacturers and can be found in general electrical or electronic catalogs such as the Newark catalog.

                McMaster-Carr    213-692-5911
                Omega Engineering       800-622-2378
                Newark           312-784-5100

Refer to National Fire Protection Association regulation NFPA-496 for detailed requirements.

These motors can accomodate rapid acceleration and deceleration. The brushless construction is made for reliability. The brushless resolver can be used as the feedback device. There is high torque to inertial ratio and stall torques from 14 to 451 lb-ins. The unique structure allows maximum power ratings, anti cog design and long life bearings.

Frame size selection:

The 3.25 inch square frame brushless motors (R30 series) include motors with continuous output torque ranging from 15 to 30 inch lb. (1.7-3.4 Nm), or momentary peak torque from 30 to 70 inch lb. (3.4 - 7.9 Nm). Rotor inertia from .17 to .31 oz-in². Continuous output power of 700 to 975 watts.

The 4.25 inch square frame brushless motors (R40 series) include motors with continuous output torque ranging from 35 to 60 inch lb. (3 - 6.8 Nm), or momentary peak torque from 70 to 14 inch lb. (7.9 - 15.8 Nm). Rotor inertia from .39 to 1.3 oz-in². Continuous output power of 900 to 1500 watts.

The 5.75 inch square frame brushless motors (R60 series) include motors with continuous output torque ranging from 75 to 150 inch lb. (8.4-16.9 Nm), or momentary peak torque from 150 to 350 inch lb. (16 - 39 Nm). Rotor inertia from 2.6 to 5.79 oz-in². Continuous output power of 2600 to 3400 watts.

The 7.5 inch square frame brushless motors (R80 series) include motor with continuous output torque ranging from 160 to 400 inch lb. (18 - 46 Nm), or momentary peak torque from 400 to 1000 inch lb. (45 - 113 Nm). Rotor inertia from 15 to 36.7 oz-in². Continuous output power of 5900 to 7800 watts.

Note: Power output is dependent upon cooling capacity of mounting or system.