ABB CM Manuals

ABB Automation Inc. Substation Automation and Protection Division Coral Springs, FL 33065 Instruction Leaflet All possible contingencies which may arise during installation, operation or maintenance, and all details and variations of this equipment do not purport to be covered by these instructions. If further information is desired by purchaser regarding this particular installation, operation or maintenance of this equipment, the local ABB Power T&D Company Inc. representative should be contacted. Printed in U.S.A. ! CAUTION Before putting relays into service, remove all blocking which may have been inserted for the purpose of securing the parts during shipment, make sure that all moving parts operate freely, inspect the contacts to see that they are clean and close properly, and operate the relay to check the settings and electrical connections. 1.0 APPLICATION The type CM relay is an induction type relay designed to protect polyphase electrical machinery against phase unbalance or phase failure. As shown in figure 6 the relay may be used with either three or two-current transformers. With three ct’s the accuracy class must be at least C50; with two ct’s the accuracy class must be at least C70. Other- wise ct errors during motor starting may cause undesired CM tripping. 2.0 CONSTRUCTION & OPERATION The type CM relay consists of two main current units and their associated resistor and an indicating con- tactor switch (ICS), or an ac indicating contactor switch (ACS). The principal component parts of the relay and their location are shown in figures 1 and 2. 2.1. MAIN UNIT Each main unit has a pair of electromagnets operat- ing on a single disc. The disc is damped by a perma- nent magnet. Each disc carries its own set of contacts with the two sets being connected in paral- lel, in order that either disc may close the trip circuit. The electromagnet pair are mounted face to face on opposite sides of the disc, and so connected that the electrical torque of one electromagnet opposes that of the other, thus producing balanced operating torque on the disc when the magnitudes of the cur- rents through each of the two electromagnets are equal. One of the electromagnets on the lower disc is connected in series with one of the electromagnets on the upper disc. Thus phase A current may balance phase B current on the upper disc, and phase B cur- rent balance C current on the lower disc. Conse- quently with balanced system conditions, no operating torque is produced on the two discs, but with unbalanced conditions or an open phase the bal- ance on the disc is upset and one or two sets of con- tacts close. Each electromagnet has a main coil located on the center leg of an “E” type laminated structure that pro- duces a flux which divides and returns through the outer legs. A shading coil located on one of the outer legs of the “E” structure causes the flux through that leg to lag the main pole flux. The out-of-phase fluxes thus produced in the air gap will cause disc rotation. A resistor located to the rear of each main unit is used as an aid in balancing the opposing torques by controlling the current flow through the shading coils. For some CM relays, the front electromagnet may have adjustable plugs which are used to aid in cali- bration. 41-181.2K Effective: June 1980 Supersedes I.L. 41-181.2J, dated March 1978 ( | ) Denotes Change Since Previous Issue Type CM Phase Balance Current Relay 41-181.2K 2 Figure 1a. Non-Tapped Type CM Relay without case (Front View Figure 1b. Non-Tapped Type CM Relay without case (Rear Vies) 3 41-181.2K Figure 2a. Type CM Tapped Relay without case (Front View) Figure 2b. Type CM Tapped Relay without case (Rear View) 41-181.2K 4 The contacts are single-pole, double throw. The moving contact is fastened directly to the disc shaft and the electrical connection is made thru a spiral spring fastened to the moving contact arm and frame assembly. 2.2. INDICATING CONTACTOR SWITCH (ICS) The dc indicating contactor switch is a small clapper type device. A magnetic armature, to which leaf- spring mounted contacts are attached, is attracted to the magnetic core upon energizing of the switch. When the switch closes, the moving contacts bridge two stationary contacts, completing the trip circuit. Also during this operation two fingers on the arma- ture deflect a spring located on the front of the switch, allowing the operation indicator target to drop. The front spring, in addition to holding the target, pro- vides restraint for the armature and thus controls the pickup value of the switch. 2.3. AC INDICATING CONTACTOR SWITCH (ASC) The ac indicating contactor switch unit is a small ac operated clapper type device. A magnetic armature, to which leaf-spring mounted contacts are attached, is attracted to the magnetic core upon energization of the switch. When the switch closes, the moving con- tacts bridge two stationary contacts completing the trip circuit. Also, during the operation, two fingers on the armature deflect a spring located on the front of the switch which allows the operation indicator target to drop. 3.0 CHARACTERISTICS The non-tapped type CM relay has a minimum pickup current of one ampere and a continuous ther- mal rating of seven amperes. The tapped CM relay has a minimum pickup of 1, 2 or 3 amperes, depend- ing on the tap setting and a continuous of 7 amperes. The minimum pickup current is defined as the pickup current of each electromagnet with the other paired electromagnet de-energized. The relay may be utilized for continuous load cur- rents of from one to seven amperes. The characteris- tic curve of the relay is shown in figure 3. 3.1. TRIP CIRCUIT The main contacts will safely close 30 amperes at 250 volts dc and the seal-in contacts of the indicating contactor switch will safely carry this current long enough to trip a circuit breaker. The indicating contactor switch (ICS) has two taps that provide a pickup setting on 0.2 or 2 amperes. To change taps requires connecting the lead located in front of the tap block to the desired setting by means of a screw connection. For 0.5 ampere ACS, the 1 second coil rating is 18.0 amperes ac. For 1.0 ampere ACS, the 1 second coil rating is 44.0 amperes ac. 3.2. TRIP CIRCUIT CONSTANTS Contactor Switch – ICS 0.2 ampere tap - 6.5 ohms dc resistance 2.0 ampere tap - 0.15 ohms dc resistance ACS 0.5 ampere ACS - 18 ohms ac impedance 1.0 ampere ACS - 4.5 ohms ac impedance 4.0 ENERGY REQUIREMENTS The burden of each electromagnet is as follows: Figure 3. Typical Operating Curve of the Type CM Relay 188A145