FAQ about Peltier Air Conditioner
Q:Do I need a well-regulated DC power
supply for my thermoelectric system?
A:This would only be required if you need wellregulated power for other circuitry that will run from the same supply. Nonetheless, many customers choose regulated switching supplies for thermoelectric systems out of consideration for size, weight, and efficiency. In high volume applications, some users have effectively employed custom, non-regulated switchers to strike a good compromise between price and performance. Those who want to keep things simple, can use a non-regulated, linear supply with a 'brute force' filter capacitor; these circuits do tend to be bulky, however. In this latter case, ripple should be kept below 15% to maximize power output to the TE modules. Unfiltered DC (i.e., rectification only) is very inefficient and quite problematic if the peak voltage exceeds VMax .
Q:Are the Peltier devices purely resistive?
A:They are mostly resistive. While there is some capacitance in a Peltier device, it is very negligible, and given the fact that DC is applied, it presents no real barriers in applications. Inductive effects are mostly confined to the leads of the Peltier device and typically present few problems unless the device is being driven with some form of pulsed DC. If this type of power is employed, it may be advisable to shield the leads and keep them separated from any signal wiring to minimize difficulties. You will see transient inductive effects in the leads whenever power is switched on or off; if these could be problematic, take precautions. The most notable non-resistive characteristic is Seebeck effect. Just as charge carriers can move heat, the movement of heat through an electrical conductor will carry charge carriers along with it. Thus, whenever a temperature difference is placed across a TE device, a small voltage will develop. If an electrical load is placed across the device in this state, current will flow. This phenomenon is called "Seebeck effect" (see FAQ on power generation technology).. Similarly, when a Peltier device is placed under power and a ΔT develops, the ΔT creates a 'back EMF' (or 'back voltage') which opposes the applied voltage. This 'Seebeck voltage' is not something that you can see or measure while external voltage is powering the Peltier device, but the circuit acts as if the Seebeck voltage is subtracted from the applied voltage. This, naturally, results in a lower current level than you might otherwise expect and makes the Peltier device appear to be more resistive than it really is. Incidentally, you can measure the Seebeck voltage when TE power is disrupted, although as the ΔT decreases from the back flow of heat, the Seebeck voltage will gradually decay to zero.
A:This would only be required if you need wellregulated power for other circuitry that will run from the same supply. Nonetheless, many customers choose regulated switching supplies for thermoelectric systems out of consideration for size, weight, and efficiency. In high volume applications, some users have effectively employed custom, non-regulated switchers to strike a good compromise between price and performance. Those who want to keep things simple, can use a non-regulated, linear supply with a 'brute force' filter capacitor; these circuits do tend to be bulky, however. In this latter case, ripple should be kept below 15% to maximize power output to the TE modules. Unfiltered DC (i.e., rectification only) is very inefficient and quite problematic if the peak voltage exceeds VMax .
Q:Are the Peltier devices purely resistive?
A:They are mostly resistive. While there is some capacitance in a Peltier device, it is very negligible, and given the fact that DC is applied, it presents no real barriers in applications. Inductive effects are mostly confined to the leads of the Peltier device and typically present few problems unless the device is being driven with some form of pulsed DC. If this type of power is employed, it may be advisable to shield the leads and keep them separated from any signal wiring to minimize difficulties. You will see transient inductive effects in the leads whenever power is switched on or off; if these could be problematic, take precautions. The most notable non-resistive characteristic is Seebeck effect. Just as charge carriers can move heat, the movement of heat through an electrical conductor will carry charge carriers along with it. Thus, whenever a temperature difference is placed across a TE device, a small voltage will develop. If an electrical load is placed across the device in this state, current will flow. This phenomenon is called "Seebeck effect" (see FAQ on power generation technology).. Similarly, when a Peltier device is placed under power and a ΔT develops, the ΔT creates a 'back EMF' (or 'back voltage') which opposes the applied voltage. This 'Seebeck voltage' is not something that you can see or measure while external voltage is powering the Peltier device, but the circuit acts as if the Seebeck voltage is subtracted from the applied voltage. This, naturally, results in a lower current level than you might otherwise expect and makes the Peltier device appear to be more resistive than it really is. Incidentally, you can measure the Seebeck voltage when TE power is disrupted, although as the ΔT decreases from the back flow of heat, the Seebeck voltage will gradually decay to zero.
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