ABB TD-5 Instruction Leaflet page 4

41-579.11B
2.1 REFERENCE VOLTAGE CIRCUITS
The reference voltage circuit provides a fixed supply voltage
to the R-C time delay circuit and protects the static
components from high voltages. It consists of a silicon
power regulator and a series resistor.
The silicon power regulator (Z or Z1) is a 10 watt Zener
diode mounted on an aluminum heat sink. The series
resistor (RS) is a 3-1/2 inch 40 W resistor which is tapped
for 24/32 VDC and 48/125 VDC relays, and fixed for 250
VDC relays.
2.2 RHEOSTAT (T) AND SCALE PLATE
The rheostat (T) provides a variable resistance for the
R-C time delay circuit. The timing scale is non-linear,
as explained in Section 2.4, Printed Circuit Board.
Please note, do not remove the knob from the rheostat
shaft, since it is not easy to replace the knob in the
calibrated position.
2.3 POTENTIOMETER (P)
The potentiometer (P) is a 2 inch wire-wound adjustable
resistor. (See Figure 1 respectively). The adjustable
terminal on the resistor should not be loosened at any
time, unless the relay is being re-calibrated.
The potentiometer (P) provides a biasing voltage, which
keeps the silicon-controlled rectifier (SCR) turned off until
the capacitor voltage reaches the potentiometer brush
voltage. The same functionality is achieved when (P) is
an adjustable resistor. For simplicity, (P) will be referred
to as a potentiometer throughout this IL. Reference to
the potentiometer's brush is equivalent to the adjustable
terminal on the adjustable resistor.
4
Type TD-5 Class 1E Time Delay Relay
2.4 PRINTED CIRCUIT BOARD
The printed circuit board (Timer Module assembly) con-
tains the following components:
(see Figure 2):
•
Diode D1 to protect the static components in case
the TD-5 relay is connected with reverse polarity.
•
Limiting timing resistor RL.
•
Timing capacitor(s) C1 to C7.
•
Resistor RP parallel to C, which makes the calibrating
scale non-linear.
•
Silicon-controlled rectifier SCR.
•
Diode D2 to reverse bias the SCR.
•
Diode D3 to protect the static components from the
inductive voltage kick associated with the coil of the
TR relay.
•
Series diodes D4, D5 & D6 to compensate for the
forward voltage drop through the SCR and D2, and
also compensate for zener (Z1) reference variations
•
Filter capacitors C8, C9 & C10.
•
Miniature power relays TR and TX, see Sections 2.5
and 2.6 respectively.
•
Varistors VR1 to VR5 across TR and TX relay
contacts.
•
Adjustable resistor P, see Section 2.3.
•
Silicon power regulator Z1, and resistor RS, see
Section 2.1.
•
Resistors R1, R2 connected in series with TX coil,
see Section 2.6
•
Resistor R3, capacitor C11, and zener Z2 to protect
the static components from the inductive voltage
kick associated with the coil of the TX relay, see
Section 2.6.
•
Zener diodes Z3 and Z4.
•
Jumper JP1 to select voltage rating.