A relay is a sensitive device provided to ensure the proper functioning of an apparatus either in the electrical circuit or in the fluid circuit and to safe guard the apparatus during any abnormalities.
*As per working principle in locomotive relays may be classified :
1. Electrical relay ( which work with electrical supply)
2. Mechanical relay ( which works with air or oil flow or pressure or by heat etc.)
Since relays are switches the terminology applied to the switches is also applied to the energising the coil in relays. A relay will switch one or more poles, each of whose contacts can be thrown by one of the three ways -
Normally Open (NO) :
Contacts connect the circuit when the relay activated, the circuit is disconnected when the relay is inactive. It is also called a Form A contact or "Make contact".
Normally Close (NC) :
Contacts are disconnect the circuit when the relay activated, the circuit is connected when the relay is inactive. It is also called Form B contact or " Brake contact".
Change Over (CO) or Double throw (DT) contact :
Contacts control two circuits, one normally open contact and one normally closed contact with a common terminals. It is also called Form C contact or brake before make contact. If this type of contact utilizes a make before break functionally, then it is called a Form D contact.
ELECTRICAL RELAYS
An electrical relay is sensitive to electricity and it is of two kinds :
(a). Voltage or Tension relay
(b). Current or Intensity relay
(1). No or /low voltage relay and
(2). Over voltage relay.
(1). No or Low voltage relay : This relay checks the voltage of auxiliary transformer TFWA. This relay is connected between the two terminals of the source supply of TFWA. The interlock of this relay is provided in the control circuit (Q-44 branch). In case there is no or low voltage at the source of supply, it de-energised and its interlock opens on the control circuit of Q-44 to open D.J.
USE ON LOCO - Q-30.
(2). Over voltage relay : This relay is connected across the two terminals (+Ve & -Ve of RSI block and its interlock is provided in the control circuit. In case there is over voltage in the traction motor its interlock closes on the control circuit and relay Q-51 energises cause auto regresssion of G.R.
USE ON LOCO - Q-20.
1. Over current relay
2. Difference of current or current differential relay.
(1). Over current relay : This relay is provided in the feeding and traction power circuit in which the over current is to be checked and the interlock is provided in the control circuit. If there is over current in the concerning circuit the relay energises and the interlock of the relay will open in the control circuit of DJ to open it.
USE ON LOCO - QLM, QRSI-1 and QRSI-2 and also QLAon some locos.
(2). Difference of current or current differential relay : This relay is connected in the traction power circuit with the two groups of traction motors in series in which the difference of current is to be checked, and the interlock is provided in the control circuit. If there isa difference of current of 160Amps between the groups of motors its interlock will close in the control circuit of Q-48 to cause auto regression of G.R., auto sanding and LSP glowing.
USE ON LOCO - QD1 and QD2.
MECHANICAL RELAYS
The relays, which work by mechanical means, are called mechanical relays. The controlling device is provided in the circuit in which circulation, pressure, temperature or speed is to be checked and the interlock is provided in the control circuit. These relays are of four types namely :
(a). Circulation relay
(b). Pressure relay
(c). Temperature relay
(d). Speed relay
A. Circulation relay : The controlling device of this type of relay is provided in the fluid (air). Circuit to check air circulation and the interlock is provided in the control circuit.
If there is no circulation or improper circulation of fluid (air) its interlock will open in the control circuit to open D.J.
USE ON LOCO : QVSI-1, QVSI-2, QVSL-1, QVSL-2, QVRH, QVMT1, QVMT-2 (all checks air circulation).
B. Pressure relay/Pressure switch : The controlling device of this type of relay is provided on the pipeline of the fluid (air circulation/oil) and the interlock is provided in the control circuit.
USE ON LOCO : QPH (check pressure of oil), QPDJ (check pressure of air)
N.B. Pressure switches provided on loco are RGCP,RGEB, RGAF, P-1, P-2 etc.
C. Temperature relay : Not provided on Loco
D. Speed relay : Not provided on Loco
All the safety relays are provided with a red target of connecting relays droops. To reset the red target it is necessary to operate the resetting knob.
USE ON LOCO : QLM,QRSI-1, QRSI-2, QOA, QOA, QOP-1 and QOP-2, on some loco QLA also.
B. Temporised or time lag relay : The relays which, after energizing or de-energising takes some time (A few seconds) to close or open its interlock on the control circuit, is called a temporised or time lag relay.
These types of relays may either be electrically time lag or mechanically time lag.
a). On delay relay - QTD 105, QTD 106, QSVM (in STC loco)
b). Off delay relay - Q-118(Temporised for 5 sec.), Q-44 (Temporised for 0.6 sec.)
C). Signalling Relays - The relay used for indication of different signalling lamps are called signalling relays.
USE ON LOCO : QV-60, QV-61, QV-62, QV-63, QV-64, QVLSOL etc.
*As per working principle in locomotive relays may be classified :
1. Electrical relay ( which work with electrical supply)
2. Mechanical relay ( which works with air or oil flow or pressure or by heat etc.)
Since relays are switches the terminology applied to the switches is also applied to the energising the coil in relays. A relay will switch one or more poles, each of whose contacts can be thrown by one of the three ways -
Normally Open (NO) :
Contacts connect the circuit when the relay activated, the circuit is disconnected when the relay is inactive. It is also called a Form A contact or "Make contact".
Normally Close (NC) :
Contacts are disconnect the circuit when the relay activated, the circuit is connected when the relay is inactive. It is also called Form B contact or " Brake contact".
Change Over (CO) or Double throw (DT) contact :
Contacts control two circuits, one normally open contact and one normally closed contact with a common terminals. It is also called Form C contact or brake before make contact. If this type of contact utilizes a make before break functionally, then it is called a Form D contact.
ELECTRICAL RELAYS
An electrical relay is sensitive to electricity and it is of two kinds :
(a). Voltage or Tension relay
(b). Current or Intensity relay
A. Voltage relay or tension relay :
The relay ,which works on voltage, is known as voltage relay. They are two kinds :(1). No or /low voltage relay and
(2). Over voltage relay.
(1). No or Low voltage relay : This relay checks the voltage of auxiliary transformer TFWA. This relay is connected between the two terminals of the source supply of TFWA. The interlock of this relay is provided in the control circuit (Q-44 branch). In case there is no or low voltage at the source of supply, it de-energised and its interlock opens on the control circuit of Q-44 to open D.J.
USE ON LOCO - Q-30.
(2). Over voltage relay : This relay is connected across the two terminals (+Ve & -Ve of RSI block and its interlock is provided in the control circuit. In case there is over voltage in the traction motor its interlock closes on the control circuit and relay Q-51 energises cause auto regresssion of G.R.
USE ON LOCO - Q-20.
B. Current or intensity relay :
The current or intensity relay is that which is sensitive to the flow of current. They are of two kinds :1. Over current relay
2. Difference of current or current differential relay.
(1). Over current relay : This relay is provided in the feeding and traction power circuit in which the over current is to be checked and the interlock is provided in the control circuit. If there is over current in the concerning circuit the relay energises and the interlock of the relay will open in the control circuit of DJ to open it.
USE ON LOCO - QLM, QRSI-1 and QRSI-2 and also QLAon some locos.
(2). Difference of current or current differential relay : This relay is connected in the traction power circuit with the two groups of traction motors in series in which the difference of current is to be checked, and the interlock is provided in the control circuit. If there isa difference of current of 160Amps between the groups of motors its interlock will close in the control circuit of Q-48 to cause auto regression of G.R., auto sanding and LSP glowing.
USE ON LOCO - QD1 and QD2.
MECHANICAL RELAYS
The relays, which work by mechanical means, are called mechanical relays. The controlling device is provided in the circuit in which circulation, pressure, temperature or speed is to be checked and the interlock is provided in the control circuit. These relays are of four types namely :
(a). Circulation relay
(b). Pressure relay
(c). Temperature relay
(d). Speed relay
A. Circulation relay : The controlling device of this type of relay is provided in the fluid (air). Circuit to check air circulation and the interlock is provided in the control circuit.
If there is no circulation or improper circulation of fluid (air) its interlock will open in the control circuit to open D.J.
USE ON LOCO : QVSI-1, QVSI-2, QVSL-1, QVSL-2, QVRH, QVMT1, QVMT-2 (all checks air circulation).
B. Pressure relay/Pressure switch : The controlling device of this type of relay is provided on the pipeline of the fluid (air circulation/oil) and the interlock is provided in the control circuit.
USE ON LOCO : QPH (check pressure of oil), QPDJ (check pressure of air)
N.B. Pressure switches provided on loco are RGCP,RGEB, RGAF, P-1, P-2 etc.
C. Temperature relay : Not provided on Loco
D. Speed relay : Not provided on Loco
OTHER RELAYS PROVIDED ON LOCO
A. Safety relay: The relays used on the control circuit of DJ and their normally closed, inter locks are provided in MTDJ branch to open DJ immediately, are called the safety relays.All the safety relays are provided with a red target of connecting relays droops. To reset the red target it is necessary to operate the resetting knob.
USE ON LOCO : QLM,QRSI-1, QRSI-2, QOA, QOA, QOP-1 and QOP-2, on some loco QLA also.
B. Temporised or time lag relay : The relays which, after energizing or de-energising takes some time (A few seconds) to close or open its interlock on the control circuit, is called a temporised or time lag relay.
These types of relays may either be electrically time lag or mechanically time lag.
a). On delay relay - QTD 105, QTD 106, QSVM (in STC loco)
b). Off delay relay - Q-118(Temporised for 5 sec.), Q-44 (Temporised for 0.6 sec.)
C). Signalling Relays - The relay used for indication of different signalling lamps are called signalling relays.
USE ON LOCO : QV-60, QV-61, QV-62, QV-63, QV-64, QVLSOL etc.
