MK Diamond Baldor Motor - Manual (Page 20)

2-10 Installation & Operation MN428
1. Motor load exceeding service factor nameplate value
2. Ambient temperatures above nameplate value
3. Voltages above or below nameplate value
4. Unbalanced voltages
5. Loss of proper ventilation
6. Altitude above 3300 feet / 1000 meters
7. Severe duty cycles of repeated starts
8. Motor stall
9. Motor reversing
10. Single phase operation of polyphase equipment
11. Variable frequency operation
Variable Frequency Power Operation for Division 1 or 2 and Zone 1 or 2 and Zone 21 or 22
Hazardous Location (motors with maximum surface temperature listed on the nameplate).
Only motors with nameplates marked for use on inverter (variable frequency) power, and labeled for specific
hazardous areas may be used in those hazardous areas on inverter power. The motor is designed to operate
at or below the maximum surface temperature (or T−Code) stated on the nameplate.
Failure to operate the motor properly can cause this maximum surface temperature to be exceeded.
If applied in a Division 1 or 2 / Zone 1 or 2 and Zone 21 or 22 environment, this excessive temperature may
cause ignition of hazardous materials. Operating the motor at any of the following conditions can cause the
marked surface temperature to be exceeded.
1. Motor load exceeding service factor nameplate value
2. Ambient temperature above nameplate value
3. Voltage (at each operating frequency) above or below rated nameplate value
4. Unbalanced voltages
5. Loss of proper ventilation
6. Operation outside of the nameplate speed / frequency range
7. Altitudes above 3300 feet / 1000 meters
8. Single phase operation of polyphase equipment
9. Unstable current wave forms
10. Lower than name plate minimum carrier frequency
Thermal Limiting
Thermal limiting devices are temperature sensing control components installed inside the motor to limit
the internal temperature of the motor frame by interrupting the circuit of the holding coil of the magnetic
switch or contactor. They are required for most Division 1 and Zone 1 applications. For Division 2 or Zone
2 applications, motors should be selected that preclude running temperatures from exceeding the ignition
temperatures for the designated hazardous material. In Division 2 or Zone 2 classified locations, thermal
limiting devices should only be used for winding protection and not considered for limiting all internal motor
temperatures to specific ignition temperatures.
Equipotential Bonding and Shaft Current Reduction
Larger motors (ie WP construction) may require proper bonding between motor enclosures and covers to
avoid the risk of stray currents during start up. Fastening methods and bonding straps must not be modified.
Bearing currents can exist in some motors for both line−fed and inverter−fed applications. Larger line−fed
motors may require at least one insulated bearing to prevent a flow of current through the bearings. Do not
defeat such insulation whether the motor is line−fed or inverter−fed applications. Inverter−fed motors may
require additional bearing insulation or even a shaft brush. Do not defeat such features. When the motor and
the coupled load are not on a common conductive baseplate, it may also be necessary to electrically bond
together the stationary parts of the motor and the coupled equipment.