Empire Magnetics Inc.: Hazardous Area Brushless Motors - Frame Size 3.25 (R30 Series)

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. Airlines, 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.

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.

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 gases 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 auto ignition 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.
Motors with temperature sensors require a setpoint temperature controller. Time delay relays are available from most major relay manufacturers and can be found in general electrical or electronic catalogs.
Refer to National Fire Protection Association regulation NFPA-496 for detailed requirements.

These motors can accommodate 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 inertia 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.

Model No.: PT-R32, PT-R33, PT-R34, PT-R35