Lloyd LS1 - 6 Power Supplies; Mains Connections; DC Supplies

LS SERIES SERVICE MANUAL
ISSUE 4.0 POWER SUPPLIES 1
6. POWER SUPPLIES
6.1 Mains Connections
The mains input is connected to a standard IEC 3 pin fused socket on the rear of the machine
that contains an RF suppression filter to reduce the emissions from the machine into the mains
supply. This filter is NOT designed to protect the machine from mains borne interference
or fluctuations, so an external line filter may be required if these effects are present.
The machine complies with the electrical safety grade of Class 1, which means that it is an
EARTHED apparatus and requires the mains plug to contain a protective earth terminal. The
mains lead MUST be connected to a mains socket, which contains a protective earth
contact.
IT IS ESSENTIAL THAT IF ANY OF THE EARTH CONNECTIONS ARE REMOVED DURING
MAINTENANCE, THEY SHOULD BE REPLACED SECURELY BEFORE THE MACHINE IS
SWITCHED ON AGAIN. THIS IS TO ENSURE THAT THE MACHINE WILL MEET THE
CLASS 1 REQUIREMENTS FOR ELECTRICAL SAFETY.
See Figure 1
The machine has been designed to operate from AC power ONLY and can be connected to a
range of mains voltages by altering the voltage selector on the mains input socket. The 115V
range will allow operation from 100V to 125V and the 230V range will allow operation from 200V
to 250V. Both lines of the AC supply are fused then switched by the user ON/OFF switch and
the emergency stop switch.
The electronic circuits are fed from two power supplies, which are powered directly from the AC
mains input supply. The digital and analogue circuits are fed from a switch mode power supply
with 3 outputs of +5, +15V and -15V. The motor drive circuits are fed from a conventional
transformer, which is fed from the mains via the series/parallel primary switching built into the
mains socket. The secondary is connected to the PCB mounted rectifier to produce either a
+45V DC or a +65V DC supply to power the PWM motor driver IC.
6.2 DC Supplies
The Analogue and Digital power supplies of +5V, +15V and -15V are fed from the switch mode
power supply to P11 on the Main PCB. The loadcell is powered from these supplies via the 16-
way IDC connector P8 on the Main PCB. The Motor Drive PCB is powered from these supplies
via the 26-way IDC connector P7 on the Main PCB. An optional external extensometer is
powered from these supplies via the 40-way IDC connector P1 on the Main PCB.
The Motor Drive PCB also requires a high current motor supply and an internally generated
+12V reference voltage. These supplies are produced using a chassis mounted toroidal
transformer together with a bridge rectifier (BR1) and smoothing capacitor (C2) on the Motor
Drive PCB.