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The following is a brief summary of the new paragraphs in the Standard for Impedance
Protected Motors UL 1004-2, which have a future Effective Date of September 16,
2013.
Subject 2521 (1004-2)
SUMMARY OF TOPICS
The following changes in requirements are being proposed:
1. The proposed first edition of UL 1004-2, Impedance Protected Motors, which
includes the following changes: a) Addition of the "no-load" condition as a
possible "worst case"; b) Exception for capacitors evaluated to UL 810; and c)
Exception for motors not exceeding 100°C under locked rotor conditions
STP BALLOTS & COMMENTS DUE: JANUARY 15, 2008
Reviewed by:
Copyright © 2007 Underwriters Laboratories Inc.
1. The proposed first edition of UL 1004-2, Impedance Protected Motors, which
includes the following changes: a) Addition of the "no-load" condition as a
possible "worst case"; b) Exception for capacitors evaluated to UL 810; and c)
Exception for motors not exceeding 100°C under locked rotor conditions
RATIONALE
Proposal submitted by Frank Ladonne, UL
UL proposes the first edition of UL 1004-2, Impedance Protected Motors. The proposed
UL 1004-2 is a standard which is part of a series of standards. UL 1004-1, Rotating
Electrical Machines - General Requirements, addresses the general requirements for all
rotating machinery, and subsequent standards in the series, such as UL 1004-2,
address the particular product requirements and cover specific constructions.
The UL 1004 series is a consolidation and rewrite of UL 1004, 1004A, UL 1004B, and
UL 2111. The rewrite and consolidation of the rotating machinery requirements is
intended to result in Standards and requirements that are more reflective of current and
emerging technologies such as brushless DC (BLDC) or electrically commutated motors
(ECM), servo motors, stepper motors, and the like. In addition, this is intended to result
in Standards that represent the most current technical philosophies. UL 1004, UL
1004A, UL 1004B, and UL 2111 will eventually be withdrawn after the new UL 1004-1
and series standards are published.
The following is presented as an overview of the new issues that are addressed in this
proposed Standard:
a) Addition of the "no-load" condition as a possible "worst case" - UL is proposing
to include evaluation of the "no-load" condition as a potential "worst case" from the
standpoint of motor heating. UL’s experience has demonstrated that certain impedance
protected motor designs will attain higher coil temperatures when run in the no-load
state than they attain in the locked rotor state. Consequently, the proposed
requirements specify evaluating the condition (no-load or locked rotor) that results in the
highest power consumption and considering that method as the "worst case" and the
condition under which the endurance test is to be run. See Section 41A, Locked-Rotor
or No-Load Temperature Test, and Section 41B, Endurance Test.
b) Exception for capacitors evaluated to UL 810 - Exception No. 2 to 41A.2 was
added to acknowledge that capacitors that comply with UL 810 will not remain shorted.
c) Exception for motors not exceeding 100°C under locked rotor conditions - The
Exception to 41A.4 was added since motors not exceeding 100°C under locked rotor
conditions do not pose the potential for degradation of the electrical or mechanical
integrity of insulating system components.
INTRODUCTION
1 Scope
1.1 This Standard is intended to be read together with the Standard for Rotating
Electrical Machines - General Requirements, UL 1004-1. The numbering of the Sections
in this Standard corresponds to the like numbered Sections in UL 1004-1. The
numbering of the paragraphs are unique to this Standard, and do not directly
correspond to the like numbered paragraphs in UL 1004-1. The requirements in this
Standard supplement or amend the requirements in UL 1004-1. The requirements of UL
1004-1 apply unless modified by this Standard. For Sections not shown, refer to the
Standard for Rotating Electrical Machines - General Requirements, UL 1004-1.
1.2 This Standard applies to motors that rely solely upon the impedance of the motor
windings to prevent overheating.
1.3 This Standard applies to motors rated 600 volts or less.
1.4 This Standard does not apply to:
a) Motors employing a device that serves as a motor protector and a
manual motor controller;
b) Motors employing a motor protector with contacts that control a relay
coil in a motor starter;
c)
Sealed (hermetic) type compressor motors; or
d)
Impedance protected motors employing an automatic starting switch.
PERFORMANCE
29 General
29.1 A motor that uses alternate types of outer wrap tape or uses alternate bobbin
materials shall have each material subjected to the Locked-Rotor or No-Load
Temperature Test, Section 41A, and the Endurance Test, Section 41B. Following the
tests, the tape and/or bobbin shall not shift or distort to result in a reduction of spacings
or to expose uninsulated live parts.
41A Locked-Rotor or No-Load Temperature Test
41A.1 Three motors are to be stalled, and the locked rotor wattage of each measured.
The same three motors are to be run no-load. The sample exhibiting the highest
wattage in either condition is then to be either locked in a stationary position using a
means of low thermal conductivity or allowed to run no-load (whichever condition results
in the highest wattage consumption).
41A.2 Testing of a permanent-split capacitor motor is to be conducted with the capacitor
either properly connected in the circuit or short-circuited, whichever results in the higher
temperature.
Exception No. 1: A motor that employs an integrally mounted and enclosed capacitor is
not required to be tested with the capacitor short-circuited.
Exception No. 2: A motor that employs a capacitor evaluated to the construction and
testing requirements in the Standard for Capacitors, UL 810, is not required to be tested
with the capacitor short-circuited.
41A.3 Temperatures are to be measured:
a)
By the change-in-resistance method; or
b) With a thermocouple applied directly to the actual conductor material,
integrally applied conductor insulation, or coil wrap, as applicable.
41A.4 Starting at room temperature, the motor is to be energized continuously for 72
hours, during which the winding temperatures are to be monitored continuously until
thermal equilibrium is attained and then continuously for the final hour.
Exception: The test may be discontinued when the winding temperatures stabilize at a
constant temperature not exceeding 100°C (212°F). The Endurance Test, Section 41B,
is not required to be performed.
41A.5 During the 72 hours, the motor shall comply with all of the following:
a) The coil temperature shall not exceed the temperature limits
specified in Table 41A.1.
b)
The fuse in the grounding conductor shall not open.
c) The motor shall still be capable of operating electrically. For example,
a bearing failure is considered in compliance.
d)
There shall be no flaming or severe or prolonged smoking.
e) There shall be no flaking, embrittlement or charring of the insulation.
Simple discoloration of the insulation meets the intent of the requirement,
and charring or embrittlement to the extent that the insulation flakes off or
material is removed when the windings are rubbed with the thumb does
not meet the intent of the requirement.
f) There shall be no electrical or mechanical malfunction of any
associated component parts such as capacitors.
g)
A secondary protector shall not have operated.
Table 41A.1
Maximum temperatures - Locked rotor or no load temperature test
Motor insulation system
Maximum temperature
°C
(°F)
Class A
150
(302)
Class E
165
(329)
Class B
175
(347)
Class F
200
(392)
Class H
225
(437)
Class N
245
(473)
Class R
265
(509)
41A.6 A polyphase motor shall additionally be tested under single phasing conditions.
The motor is to be energized with one supply conductor open circuited. The test is to be
repeated until all phases have been singly opened.
41A.7 At the request of the manufacturer, the test in this Section is to be conducted
under such conditions that result in the motor coils operating at the maximum
temperature for the insulation class specified in Table 41A.1. The maximum
temperature is to be obtained by:
a)
Increasing the test voltage;
b)
Increasing the ambient temperature;
c) Using test samples constructed so that they maintain the maximum
temperature; or
d)
Any other equivalent means.
This test shall not be conducted by increasing the voltage for motors with the capacitor
shorted.
41A.8 When a "worst-case" condition (such as speed of a multi-speed motor or
frequency) is not evident, a motor shall be tested at each condition until thermal
stabilization. The condition resulting in the highest operating temperature is then to be
subjected to the full Locked Rotor or No-load Temperature Test, Section 41A, and
Endurance Test, Section 41B.
41A.9 Immediately following the conclusion of the Locked-Rotor or No-load
Temperature Test, and while still in a heated state, a motor shall be subjected to the
Dielectric Voltage-Withstand Test, Section 36, of UL 1004-1.
41B Endurance Test
41B.1 Immediately following the Locked Rotor or No-load Temperature Test, Section
41A, a motor is to be re-energized under the conditions of that test for an additional 15
days.
41B.2 At the conclusion of the 15 days, the motor shall comply with the following:
a) There shall be no evidence of excessive deterioration of the
insulation. Simple discoloration of the insulation meets the intent of the
requirement, and charring or embrittlement to the extent that the insulation
flakes off or material is removed when the windings are rubbed with the
thumb does not meet the intent of the requirement.
b)
The fuse in the grounding conductor shall not open.
c) The motor shall still electrically operate. For example, a bearing
failure is considered in compliance.
d)
A secondary protector shall not have operated.
41B.3 Immediately following the conclusion of the Endurance Test, and while still in a
heated state, a motor shall withstand the dielectric voltage withstand test specified in
41B.4.
41B.4 There shall be no dielectric breakdown as the result of a one-minute application
of a potential of twice the marked rated voltage of the motor between the windings and
the frame.
MARKINGS
43 General
43.1 The words "Impedance-Protected" shall be marked on the outside of the motor
where visible.
Exception: A motor having a rated input of 100 watts or less may be marked "Z.P." or
"ZP" instead of "Impedance-Protected".
43.2 A motor rated 1/8 horsepower (93 W) or more shall be marked with the rated
horsepower.
43.3 An alternating-current motor rated 1/2 horsepower (373 W output) or more shall be
marked with a code letter to indicate locked-rotor amperes in accordance with the
National Electrical Code®, NFPA 70.
The National Electrical Code® and NEC® are registered trademarks of the National Fire
Protection Association, Inc., Quincy, MA 02169.
43.4 A wound-rotor induction motor shall be marked with the secondary volts and fullload amperes.
43.5 A direct-current motor shall be marked to indicate the winding type - straight shunt,
stabilized shunt, compound, or series.
43.6 A multi-speed motor, other than a shaded-pole or a permanent-split-capacitor
motor, shall be marked with the amperes and horsepower at each speed.