TE Technology TC-48-20 - Manual (Page 14)

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operating temperature. The controller can be configured to signal an alarm condition on either the control
thermistor or the secondary thermistor or both.
1.4 The TC‐48‐20 can be used with either one or two separate DC power supplies, depending primarily on the
nominal operating voltage of the TE device. If the maximum TE device input voltage is less than 9 V, then
two power supplies must be used with the controller. If the TE device can use a voltage ≥9 V but <50 V, then
the controller can be used with either one or two power supplies.
The controller can also be set up to provide linear control output when used with a power supply whose
output can be controlled with a 0 to 5 V signal. The power supply can then provide a power output
proportional to the signal sent by the controller. This setup is also useful for situations in which the TE
device requires more power than what the controller itself can directly handle. However, this setup will
reduce the overall control stability. The voltage signal from the controller is actually obtained by filtering the
PWM output, and this introduces a slight delay in the control response. Also, there will be a delay in the
response of the power supply since it too must process the correct power output based on the sensed
voltage input from the controller.
When using one power supply for powering the controller and the TE device together, the power
supply input voltage is passed directly through the controller to the TE device during the “ON”
pulse. The user should choose an input voltage that is required for the TE device and yet is also ≥9
V but <50 V. The controller could be damaged if operated outside this voltage range.
When using two power supplies, the controller input power supply must be ≥9 V but <50 V at 150
mA minimum. The power supply input voltage for the TE device can be ≥0 V but <50 V.
The maximum allowable current through the controller is 20 A. The maximum allowable current
draw for the TE device must therefore be less than 20 A depending on if and how much current is
used to power alarm signals and the controller itself. The 20 A limit applies regardless of whether
you are using one power supply or using two independent power supplies.
The controller does not have an internal fuse or circuitry to limit current. Therefore, an external
fuse, appropriately sized for protecting the controller/TE device, should be connected between the
power supply and the controller to prevent damage to the controller/TE device and to prevent
injury to the user should an over‐current condition occur. Alternately, a power supply with integral
over current protection can be used if it is appropriately sized for protecting the controller/TE
device.
When making a cooling system from a single TE device, the maximum operating voltage for that
system is usually no more than 75% of the rated Vmax of the TE module. The 75% rule is based on
the TE module being thermally connected to a “good” heat sink; system modeling should be done
to verify this rule is applicable though. If multiple TE modules are used in series or series‐parallel
combination, the Vmax of the system will be approximately 75% of the rated Vmax of each TE
module multiplied by the number of modules in series. Applying a voltage greater than the system
maximum will not necessarily damage the controller (unless voltage and/or current limits are
exceeded), but the TE device could be damaged by overheating as a result.
Power supply and TE Device wire leads should be kept as short as possible to minimize electrical
losses and reduce the likelihood of generating unwanted electromagnetic interference. Use wires
of a sufficient gage appropriate to the amount of electrical energy each wire is to carry. Wire
insulation and size must also be appropriate to the ambient temperature and/or temperature of
objects in contact with the wire. Wire leads supplied by TE Technology are for prototyping
purposes and should be reviewed for appropriateness in the final application. Wire length must not
exceed one meter. However, see also warnings about wire length under section 1.6.