Operational Electrical Parameters - VWR International 250V Instruction Manual

Operation stops Power supply is
with alarm: overheating
Display shows
"OVER TEMP"

Operational Electrical Parameters

Power Considerations
Electrophoresis is the migration of a charged particle under the influence of an electrical field.
The power supply output parameters voltage, current, and power
are related by the following two equations:
Voltage (V) = Current (I) x Resistance (R); (V=IR)
Power (W) = Current (I) x Voltage (V); (W=IV)
Resistance
Resistance of the assembled electrophoresis cell is dependent on the conductivity of the gel
buffer, the thickness of the gel, and the number of gels being run. Although the resistance is
determined by the gel system, the resistance can vary over the course of an electrophoretic
separation. For instance, in the Tris-Glycine buffer system, the fast moving, highly conductive
chloride ions in the gel are gradually replaced by the slower moving, less conductive glycine
ions from the running buffer as the gel runs. As a result, the resistance of the gel increases as
the chloride/glycine front moves down the gel, and the current decreases.
Voltage
The velocity with which an ion moves in an electric field will vary in proportion to the field
strength (volts per unit distance). The higher the voltage the faster an ion will move.
Current
Current is a function of the number of ions passing a given cross-section of the circuit at a
given time. For a given gel/buffer system, at a given temperature, current will vary in proportion
to the field strength (voltage) and/or crosssectional area (number and/or thickness of the gels).
•
Turn off power supply. Check for sufficient
airflow around the power supply fan. After
cooling down, restart the power supply by
turning the Power switch to the on position.
•
If you cannot restart the
instrument, turn off the power, disconnect
the power cord from the outlet, and contact
Technical Service.
17