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Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSINTRODUCTIONThe following represents the most up-to-date information on motor terminal marking for proper connectionto power source for all alternating current motors manufactured in accordance with standards adopted bythe National Electrical Manufacturers’ Association.In addition, this section contains important data covering internal wiring to motor terminals which willprove invaluable to the Refrigeration Service Engineer in solving motor problems.The source of this information is Part 2 of the NEMA Standards Publication, for which reprint permissionwas granted RSES by the National Electrical Manufacturers' Association.MG 1-2.01 LOCATION OF TERMINAL MARKINGSTerminal markings shall be placed on or directly adjacent to terminals to which connections must bemade from outside circuits or from auxiliary devices which must be disconnected for shipment. Whereverspecified, color coding may be used instead of the usual letter and numeral marking.*MG 1-2.02 TERMINAL MARKINGSA combination of capital letters or symbols and an arabic numeral shall be used to indicate the characteror function of the windings which are brought to the terminal.*The following letters and symbols shall be used for motors and generators and their auxiliary deviceswhen they are included within or mounted on the machine.*Resistance (shunt field adjusting)–V1, V2, V3, etc.Shunt braking resistor–DR1, DR2, DR3, DR4, etc.Space heaters–H1, H2, H3, H4, etc.‡Stator –T1, T2, T3, T4, etc.Starting switch–K.Terminal protector–P1, P2, P3, P4, etc.Equalizing lead– (equality sign).Neutral connection–Terminal letter with numeral 0.For the significance of the arabic numeral, see MG 1-2.20 for alternating-current machines.‡For alternating-current machines only.Armature–A1, A2, A3, A4, etc.Brake–B1, B2, B3, B4, etc.Alternating-current rotor windings (collector rings) ‡–M1, M2, M3, M4, etc.Capacitor–J1, J2, J3, J4, etc.Control signal lead attached to commutating winding–C.1

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSDynamic braking resistor–BR1, BR2, BR3, BR4, etc.Field (series)–S1, S2, S3, S4, etc.Field (shunt)–F1, F2, F3, F4, etc.Line–L1, L2, L3, L4, etc.Magnetizing winding (for initial and maintenance magnetization and demagnetization of permanentmagnetic fields)–E1, E2, E3, E4, etc. (NOTE–E1, E3, or other odd-numbered terminals should beattached to the positive terminal of the magnetizing power supply for magnetization and to the negativeterminal for demagnetization.) Resistance (armature and miscellaneous)–R1, R2, R3, R4, etc.* Approved as NEMA Standard 11-16-1967‡Approved as Authorized Engineering Information 11-16-67 Added as NEMA Standard 11-16-68ALTERNATING-CURRENT MOTORS AND GENERATORSMG 1-2.20 Numerals on Terminals Of Alternating-Current Polyphase MachinesA. SYNCHRONOUS MACHINESThe numerals 1, 2, 3, etc., indicate the order in which the voltages at the terminals reach theirmaximum positive values (phase sequence) with clockwise shaft rotation when facing theconnection end of the coil windings: hence, for counterclockwise shaft rotation (not standard)when facing the same end, the phase sequence will be 1, 3, 2.†B. INDUCTION MACHINESTerminal markings of polyphase induction machines are not related to the direction of rotation.†* Approved as NEMA Standard 11-16-1967†Approved as Authorized Engineering Information 11-16-1967MG 1-2.21 Definition Of Phase SequencePhase sequence is the order in which the voltages successively reach their maximum positive valuesbetween terminals.*MG 1-2.22 Phase SequenceThe order of numerals on terminal leads does not necessarily indicate the phase sequence, but the phasesequence is determined by the direction of shaft rotation relative to the connection end of the coilwinding.†MG 1-2.23 Direction Of Rotation Of VectorsVector diagrams shall be shown so that advance in phase of one vector with respect to another is in thecounterclockwise direction.2

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSSee Fig. 2-11 in which vector 1 is 120 degrees in advance of vector 2 and the phase sequence is 1, 2, 3.(See MG 1-2.21.)*MG 1-2.24 Direction Of RotationThe standard direction of rotation for alternating generators is clockwise when facing the end of themachine opposite the drive.*The direction of rotation of a generator mounted as a part of an engine-generator set is usuallycounterclockwise when facing the end opposite the drive.†The standard direction of rotation for all alternating-current single-phase motors, all synchronous motors,and all universal motors shall be counterclockwise when facing the end of the machine opposite thedrive.*MG 1-2.25 Reversal Of Rotation, Polarity And Phase SequenceAlternating-current generators driven counterclockwise when facing the connection end of the coilwindings will generate without change in connections, but the terminal phase sequence will be 1, 3, 2.†Synchronous condensers and synchronous motors may be operated with counterclockwise shaft rotationviewed from the connection end of the coil windings by connecting them to leads in which the phasesequence is 1, 2, 3, in the following manner:†Power leads. 1, 2, 3Machine terminals.1, 3, 2ALTERNATING-CURRENT GENERATORS AND SYNCHRONOUS MOTORSMG 1-2.30 Connections And Terminal Markings–Alternating-Current Generators And SynchronousMotors–One, Two, And Three PhaseThe alternating-current windings of three-phase alternating-current generators and synchronous motorsshall have terminal markings as given in MG 1-2.61 for three-phase single-speed induction motors.*The alternating-current windings of two-phase alternating-current generators and synchronous motorsshall have terminal markings as given in MG 1-2.66 for two-phase single-speed induction motors.*The alternating-current windings of single-phase alternating-current generators and synchronous motorsshall have terminal markings as given in Fig. 2-12.*3

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSThe terminal markings of direct-current field windings shall be F1 and F2.*NOTE:See MG 1-2.02 for terminal letters assigned to different types of windings and MG 1-2.20for the significance of the numerals.†SINGLE-PHASE MOTORSMG 1-2.40 GeneralA. DUAL VOLTAGERegardless of type, when a single-phase motor is reconnectible series-parallel for dual voltage,the terminal marking shall be determined as follows:*For the purpose of assigning terminal markings, the main winding is assumed to be divided intotwo halves, and T1 and T2 should be assigned to one half and T3 and T4 to the other half.*For the purpose of assigning terminal markings, the auxiliary winding (if present) is assumed tobe divided into two halves, and T5 and T6 should be assigned to one half and T7 and T8 to theother half.*Polarities shall be established so that the standard direction of rotation (counterclockwise facingthe end opposite the drive) is obtained when the main winding terminal T4 and the auxiliarywinding terminal T5 are joined or when an equivalent circuit connection is made between themain and auxiliary winding.*The terminal marking arrangement is shown diagrammatically in Fig. 2-13.*4

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSB. SINGLE VOLTAGEIf a single-phase motor is single voltage or if either winding is intended for only one voltage, theterminal marking shall be determined as follows.*T1 and T4 shall be assigned to the main winding and T5 and T8 to the auxiliary winding (ifpresent) with the polarity arrangement such that the standard direction of rotation is obtained if T4and T5 are joined to one line and T1 and T8 to the other.*The terminal marking arrangement is shown diagrammatically in Fig. 2-14.*5

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSNOTE:It has been found to be impracticable to follow this standard for the terminalmarkings of some definite-purpose motors. See Part 18.†NOTE:No general standards have been developed for terminal markings of multispeedmotors because of the great variety of methods employed to obtain multiplespeeds.†MG 1-2.41 Terminal Markings Identified By ColorWhen single-phase motors use lead colors instead of letter and number markings to identify the leads,the color assignment shall be determined from the owT5–BlackT8–RedP1–No color assignedP2–BrownNOTE:It has been found to be impracticable to follow this standard for the lead markings ofsome definite-purpose motors. See Part 18.†MG 1-2.42 Auxiliary Devices Within MotorThe presence of an auxiliary device or devices, such as a capacitor, starting switch, terminal protector,etc., permanently connected in series between the motor terminal and the part of the winding to which itultimately connects shall not affect the marking unless a terminal is provided at the junction.*Where a terminal is provided at the junction, the terminal marking of this junction shall be determined bythe part of the winding to which it is connected. Any other terminals connected to this auxiliary deviceshall be identified by a letter indicating the auxiliary device within the motor to which the terminal isconnected.*MG 1-2.43 Auxiliary Devices External To MotorWhere the capacitors, resistors, inductors, transformers or other auxiliary devices are housed separatelyfrom the motor, the terminal markings shall be those established for the device.*6

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSMG 1-2.44 Marking Of Rigidly-Mounted TerminalsOn a terminal board, the identification of rigidly-mounted terminals shall be either by marking on theterminal board or by means of a diagram attached to the machine. When all windings are permanentlyconnected to rigidly mounted terminals, these terminals may be identified in accordance with the terminalmarkings specified in this article. When windings are not permanently attached to rigidly-mountedterminals on a terminal board, the rigidly-mounted terminals shall be identified by numbers only, and theidentification need not coincide with that of the terminal leads connected to the rigidly-mounted terminals.*MG 1-2.45 Internal Auxiliary Devices Permanently Connected To Rigidly-Mounted TerminalsIf the motor design is such that the starting switch, terminal protector or other auxiliary device ispermanently connected to a rigidly mounted terminal, some variation from the connection arrangementsillustrated in MG 1-2.47 through MG 1-2.53 will be required. However, any variations shall be based onthe provisions of MG 1-2.46.*MG 1-2.46 General Principles For Terminal Markings For Single-Phase MotorsThe terminal marking and connection procedure given in MG 1-2.40 through MG 1-2.45 and in theschematic diagrams which follow are based on the following principles:†A. FIRST PRINCIPLEThe main winding of a single-phase motor is designated by T1, T2, T3 and T4 and the auxiliarywinding by T5, T6, T7 and T8 to distinguish it from a quarter-phase motor which uses oddnumbers for one phase and even numbers for the other phase.†B. SECOND PRINCIPLEBy following the first principle, it follows that odd-to-odd numbered terminals of each winding arejoined for lower voltage (parallel) connection and odd-to-even numbered terminals of eachwinding are joined for higher voltage (series) connection.†C. THIRD PRINCIPLEThe rotor of a single-phase motor is represented by a circle, even though there are no externalconnections to it. It also serves to distinguish the single-phase motor schematic diagram from thatof the quarter-phase motor in which the rotor is never represented.†* Approved as NEMA Standard 11-16-67† Approved as Authorized Engineering Information 11-16-677

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS8

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS9

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS10

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS11

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS12

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS13

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDS14

Service Application ManualSAM Chapter 620-37Section 6ATERMINAL MARKINGS AND INTERNAL WIRING DIAGRAMS SINGLE PHASE ANDPOLYPHASE MOTORS MEETING NEMA STANDARDSPOLYPHASE INDUCTION MOTORSMG 1-2.60 General Principles For Terminal Markings For Polyphase Induction MotorsA. The markings of the terminals of a motor serve their purpose best if they indicate the electricalrelations between the several circuits wit