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CHAPTER 1 INTRODUCTION Installing new electric service is a joint project between the customer and the power company ____________________________________Motors 55


CHAPTER 5

MOTORS

GENERAL

Motors connected to NAEDs system must be of a type
to use minimum starting current and must conform to
the requirements of NAED and the applicable
electrical code as to wiring, equipment type and
control devices.

Before purchasing any motor, the customer should
contact NAED to verify the nominal utilization
voltage, phase characteristics of the service to be
supplied and the, maximum allowable lock rotor
current values.

LIMITATION OF SIZE

NAED reserves the right to refuse service to the
following:


Single phase motors larger than 5hp. Single
phase motors of larger rating may be
permitted, providing NAEDs facilities are
adequate to supply the service and provided
the use of such motor does not interfere with
the quality of service to other customers.

Polyphase motors larger than 5hp operated from
a single phase service by use of a phase
converter.

NAED further reserves the right to limit the
size of the largest motor which may be
operated on any part of the system. 56 Service Requirements Handbook_____________

PROTECTION AGAINST SINGLE PHASE
OPERATION

Three phase motors shall be protected against the
possibility of the failure of any one phase of the
supply circuit through the use of three overcurrent
(overload) devices unless the motor is protected
against single phase operation by other approved
ans.
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UNDERVOLTAGE PROTECTION

Motors that cannot be safely subjected to full
voltage at starting, or motors the starting of which
on return of normal voltage after an interruption
would endanger life or property, should be provided
with automatic undervoltage protection. Such
protective device should insure that with either no
voltage or undervoltage the motor will be
disconnected from the line or the starter will be
returned to the off position.


OVERLOAD PROTECTION

All motors should be protected against overload by
the installation of adequate overcurrent thermal
devices or their equivalent in all three phases,
which will operate as to prevent excessive motor
winding temperatures.




____________________________________Motors 57

PROTECTION AGAINST PHASE REVERSAL

On motors for passenger or freight elevators, cranes,
hoists and other equipment where reversal of
direction or rotation might cause property damage or
injury, a reverse phase relay should be installed so
the motor circuit will be opened in the event of a
phase reversal or the loss of any phase. The
operation of this relay should be instantaneous.


DAMAGE TO EQUIPMENT

NAED will not be responsible for damage caused to
customer owned equipment where such damage is caused
by absence or failure of any of the above protective
devices.



















58 Service Requirements Handbook_____________