Motor Control Panel

Pre-treatment shall include:

1. Hot alkaline cleaner to remove grease and oil.
2. Iron phosphate treatment to improve adhesion and corrosion resistance.
3. The paint shall be applied using an electro-deposition process to ensure a uniform paint coat with high adhesion.
4. The paint color shall be epoxy medium light gray. Unit interior saddles shall be painted orange.

TYPICAL UNIT CONSTRUCTION

All conducting parts on the line side of the unit disconnect shall be shrouded by a suitable insulating material to prevent accidental contact with those parts.

A lever handle operator must be provided on each disconnect.  With the unit stabs engaged onto the vertical phase bus and the unit door closed, the handle mechanism shall allow complete ON/OFF control of the unit.  All circuit breaker operators shall include a separate TRIPPED position to clearly indicate a circuit breaker trip condition.  It shall be possible to reset a tripped circuit breaker without opening the control unit door. A clear indication of disconnect status shall be provided, by adhering to the following operator handle positions:

• Handle “On” position must be up or to the left and within 45 degrees of being parallel to the face of the equipment.
• Handle “Off” position must be down or to the right and within 45 degrees of being parallel to the face of the equipment.
• The minimum separation between the “On” and “Off” positions shall be 90 degrees.
• On Circuit Breaker disconnects, the handle “Tripped” position must be perpendicular to the face of the equipment +/- 30 degrees. The minimum separation between “On” and “Tripped” shall be 30 degrees. The minimum separation between “Tripped” and “Off” shall be 45 degrees.

 A mechanical interlock shall prevent the operator from opening the unit door when the disconnect is in the ON position.  It shall be possible for authorized personnel to defeat these interlocks.

COMPONENTS FOR TYPICAL UNITS

a. Combination Starters

• All combination starters shall use NEMA/EEMAC rated contactors.  Starters shall be provided with a three-pole, external manual reset, overload relay with thermal overload units.
• When provided, control circuit transformers if utilized shall include two primary protection fuses and one secondary fuse (in the non-ground secondary conductor).  The transformer shall be sized to accommodate the contractor(s) and all connected control circuit loads.  The transformer rating shall be fully visible from the front when the unit door is opened.
• When a unit control circuit transformer is not provided, the disconnect shall include an electrical interlock for the disconnection of externally powered control circuits.
• Auxiliary control circuit interlocks shall be provided where indicated.  Auxiliary interlocks shall be field convertible to normally open or normally closed operation.

b. Terminal Blocks

• When Type B wiring is specified, all starter units shall be provided with unit control terminal blocks.
• Terminal blocks shall be the pull-apart type with a minimum rating of 250 volt and 10 amps.  All current-carrying parts shall be tin-plated.  Terminals shall be accessible from inside the unit when the unit door is opened.  Terminal blocks shall be DIN rail mounted with the stationary portion of the block secured to the unit bottom plate.  The stationary portion shall be used for factory connections and shall remain attached to the unit when removed.  The terminals used for field connections shall face forward so they can be wired without removing the unit or any of its components.

c. Nameplates

• Shall be engraved phenolic nameplates for each MCC and unit compartment.  Shall be gray background with white letters, measuring a minimum of 1.5 in (38 mm) H x 6.25 in (159 mm) W total outside dimensions.

d. Pilot Device Panel

• Each starter unit shall be proved with a hinged/removable control station plate, which can accommodate up to five 22 mm pilot devices or three 30 mm pilot devices

ADJUSTABLE FREQUENCY AC DRIVE UNIT CONSTRUCTION

All AC drive controller units shall be provided with unit control terminal blocks for use in terminating field wiring.

The AC drive controller unit shall incorporate a self-contained, air-based cooling system where required. Any air exhaust vents shall be louvered to help direct airflow away from personnel operating the AC drive controller unit. Any fans, ductwork, or filters shall be easily accessible for maintenance.

Cooling

• The AC drive controller unit cooling system shall be sized to cool the drive regardless of mounting location within the MCC. The AC drive controller unit shall not be restricted to a specific location in the MCC.
• An internal over-temperature trip shall be provided to detect cooling system failure or blockage.  Upon the occurrence of an over-temperature trip, the cooling system fans shall continue running to provide a rapid cool down.
• Power for the cooling system shall be provided internal to the AC drive controller unit by use of a control power transformer that includes two primary fuses and one secondary fuse (in the non-ground secondary conductor).

Protection

• The AC drive controller unit shall be protected against fault currents
• The AC drive controller unit shall be protected against short circuits between output phases, between output phases and ground, on the internal power supplies.
• Upon loss of the analog process follower reference signal, the AC drive shall be programmable to a fault and freewheel stop, ramp stop, fast stop, stop without the trip, automatically restart, run at last speed, or maintain a user-defined low-speed setting.
• The AC drive shall include an adjustable thermal alarm which can be assigned to a relay or logic output to indicate the drive temperature has reached the thermal alarm setting.

Graphic Display Terminal Interface

• The AC drive model number, torque type, software revision number, horsepower, output current, motor frequency, and motor voltage shall all be listed on the drive identification display as viewed on the graphic display terminal.