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DOE-HDBK-1092-2004
6.3.2.4 MOTORS
Elevator and escalator motors are considered as intermittent duty. This allows them to be
protected by the overcurrent protection device supplying the power for the branch circuit, which
is selected by the percentages in NEC Table 430.22 times the full load current of the motors.
For example: What is the load for a 15-minute rated 40-hp, 460-V, three-phase motor used as a
freight elevator motor?
Step 1:
Finding full load current -- NEC Table 430.150
40 HP = 52 A
Step 2:
Finding demand factors -- NEC Table 430.22 (a)
15 minute rated = 85%
Step 3:
Calculating load
52 A x 85% = 44.2A
Answer: Load is 44.2 amps.
6.3.2.5 GROUNDING
All metal raceways and cables, Types MC, Ml, or AC, shall be bonded to the metal frame of the
car. All elevator equipment including metal enclosures for electric devices on the car shall be
grounded in accordance with NEC Article 250.
6.3.2.6 OVERSPEED PROTECTION
Overspeed protection for overhauling and under-hauling is required, as are motor-generator
overspeed requirements that must comply with NEC 430.89, Speed Limitation. However, these
requirements are a part of the more extensive requirements of ANSI/ASME A17.1 for electrical
safety devices, which require scrutiny by designers, maintenance personnel, and inspectors.
6.3.3
EMERGENCY POWER
Emergency power requirements are governed by ANSI/ASME A17.1 Rule 211.2, which requires
that the regenerative power of an overhauling elevator prevent the elevator from attaining the
lesser of the governor tripping speed or 125 percent of the rated speed. If the elevator power
system cannot absorb this power, a load shall be provided on the load side of the elevator
power disconnect switch. If an emergency power supply is designed to operate only one
elevator at a time, the energy absorption means may, if required, be located on the line side of
the disconnect. Other building loads that may be supplied by the emergency power source may
not be considered as absorbing regenerated energy unless they use the emergency power
source as normal power. Refer to Article 620, Part X, of the NEC, Overspeed, for the installation
requirements covering these requirements.
6.3.4
DESIGN
In addition to the NEC, elevator and escalator requirements, there are numerous electrical
requirements for the facilities designer in ANSI/ASME A17.1 and A17.3. A17.1 is a required
reference for new elevator and escalator installations and can be used by the designer in
checking submittal drawings from the manufacturer. ANSI/ASME A17.3 provides the safety
6-9


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