switch (D) Torque Motors. For torque motors, the controller
shall have a continuous-duty, full-load current rating not
less than the nameplate current rating of the motor. For a motor controller rated in horsepower but not marked with
the foregoing current rating, the equivalent current rating
shall be determined from the horsepower rating by using
Table 430.247, Table 430.248, Table 430.249, or Table
430.250.

(E) Voltage Rating. A controller with a straight voltage rating, for example, 240 volts or 480 volts, shall be permit

ted to be applied in a circuit in which the nominal voltage
between any two conductors does not exceed the
control
ler's voltage rating. A controller with a slash rating, for
example, 120/240 volts or 480Y/277 volts, shall only be
ap
plied in a solidly grounded circuit in which the nominal
volt
age to ground from any conductor does not exceed the
lower
of the two values of the controller's voltage rating and
the
nominal voltage between any two conductors does not
exceed
the higher value of the controller's voltage rating.

430.84 Need Not Open All Conductors. The controller shall not be required to open all conductors to the motor.

Exception: Where the controller serves also as a discon- necting means, it shall open all ungrounded conductors to the motor as provided in 430. HI.

430.85 In Grounded Conductors. One pole of the con troller shall be permitted to be placed in a permanently grounded conductor, provided the controller is designed so that the pole in the grounded conductor cannot be opened

without simultaneously opening all conductors of the
circuit.

430.87 Number of Motors Served by Each Controller.

Each motor shall be provided with an individual controller.

Exception No. 1: For motors rated 600 volts or less, a single controller rated at not less than the equivalent horsepower, as determined in accordance with

430.110(C)(1), of all the motors in the group shall be permitted to serve the group under any of the following conditions:

(a) Where a number of motors drive several parts of a single machine or piece of apparatus, such as metal and woodworking machines, cranes, hoists, and similar

apparatus

(b) Where a group of motors is under the protection

of one overcurrent device as permitted in 430.53(A)

(c) Where a group of motors is located in a single

room within sight from the controller location

Exception No. 2: A branch-circuit disconnecting means serving as the controller as allowed in 430.81(A) shall be permitted to serve more than one motor.

430.88 Adjustable-Speed Motors. Adjustable-speed motors that are controlled by means of field regulation shall be equipped and connected so that they cannot be started under a weakened field.

Exception: Starting under a weakened field shall be per- mitted where the motor is designed for such starting.

430.89 Speed Limitation. Machines of the following types shall be provided with speed-limiting devices or other speed-limiting means:

(1) Separately excited dc motors

(2) Series motors

(3) Motor-generators and converters that can be driven at excessive speed from the dc end, as by a reversal of current or decrease in load