Cutler-Hammer EATON Ampgard Mark V Manual de instrucciones

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Cutler-Hammer

Instructions For Ampgard

Brush-Type, Synchronous Motor Controllers

HAZARDOUS VOLTAGE.

READ AND UNDERSTAND THIS BOOKLET AND ITS

RELATED INSTRUCTION MATERIAL FOR FULL-

VOLTAGE CONTROLLERS IN THEIR ENTIRETY

BEFORE INSTALLING OR OPERATING THE

CONTROLLER. SEE TABLE 1.

INSTALLATION, ADJUSTMENT, REPAIR AND

MAINTENANCE OF THIS TYPE OF EQUIPMENT MUST

BE PERFORMED BY QUALIFIED PERSONNEL. A

QUALIFIED PERSON IS ONE WHO IS FAMILIAR WITH

THE CONSTRUCTION AND OPERATION OF THIS

EQUIPMENT AND THE HAZARDS INVOLVED.

SYNCHRONOUS MOTORS

Polyphase synchronous motors have stators similar to

squirrel-cage induction motors and most have rotors with

DC slip-ring circuits which must be energized for normal

operation. The controller described in this booklet is for a

synchronous motor with slip rings and brushes.

Synchronous motors operate at constant base speeds

corresponding to line frequency and the number of ma-

chine poles (revolutions/min = 120 x frequency/number of

poles). They are employed primarily to obtain high pullout

torques, constant operating speeds, or generation of

leading reactive VA (VAR) for system power-factor correc-

tion. They require conventional AC polyphase power

sources for their stators and suitable DC power sources

for their rotor fields.

For normal operation, synchronous motors must be

brought to near full operating speed, at which point the DC

power is connected to the rotating field through brushes

and slip rings. The motors are accelerated to their syn-

chronizing speeds by means of either built-in start wind-

ings or external auxiliary drives. Nearly all conventional

synchronous motors now manufactured have built-in rotor

starting windings. Such starting windings are also referred

to as squirrel-cage windings, pole-face windings, damper

windings, or amortisseur windings. Start windings are

actually squirrel-cage induction bars located in the faces

Effective 11/97

DANGER

Mark V Solid-State,

TABLE I. REFERENCE MATERIAL

Contactor

Type

Type SJA

Type SJD

Type SJO

Type SJS

of the DC rotor poles. They produce accelerating torque

only and have short-time intermittent duty ratings. As

start windings, they become inoperative at synchronous

speeds but serve to dampen any tendency of the rotor to

oscillate in angular position with relation to the stator field.

The starting of synchronous motors involves two basic

switching functions. The first is the energizing of the

stator to produce breakaway torque and acceleration to

near synchronous speed, the second is the energizing of

the DC rotor field at the optimum speed and rotor-stator

pole relationship. For motors having built-in start wind-

ings, the same equipment considerations are required as

for full-voltage or reduced-voltage starting methods used

for squirrel-cage induction motors. All factors relating to

the stator circuits are identical.

Synchronous motors have two torque characteristics,

starting torque and running or synchronous torque. The

first is determined by the squirrel-cage design and the

"slip" as the motor accelerates from zero to near synchro-

nous speed. "Slip" is expressed as a percent fraction

where the numerator is the difference between the syn-

chronous speed and the non-synchronous speed, and the

denominator is the base speed, all speeds expressed in

revolution per minute (rpm). The running torque character-

istic (at synchronous speed) is produced by the magnetic

fields created by the DC field coils in the rotor which link

with the rotating fields produced by the AC current in the

stator windings. See Figure 1.

The DC field coils are energized via two slip rings and

brushes. The DC voltage applied to the field coils can be

varied to produce the desired level of direct current which

in turn produces a magnetic field through each pole which

can be varied. Once at synchronous speed,

I.B. 48008

Ampere

Instruction

Rating

I.L. or I.B.

360A

I.B. 48002

720A

I.B. 48005

360A

I.B. 48004

360A

I.L. 16-200-33

720A

I.L. 17047

360A

I.B. 48003