Capacitor Trip Devices (CTD)
There are many different applications for and methods of using the Electromagnetic Industries products and we cannot be familiar with every particular system configuration that each of our products may be used in. For this reason we may not be able to give direct advice of how to set up your particular system. Any statements here are general statements that may or may not apply directly to your specific system configuration. We can only speak to how the Electromagnetic Industries components and products are designed to operate. Any questions concerning your complete system configuration or proper application of our products in your particular system must be addressed by your switchgear manufacturer and/or your EE.
Question: How long does it take to discharge the CTD?
Answer: The rate of discharge depends on the load across the output. The time for discharge can be determined by using the formula: t = -RC * ln (V/Vo)
Vo: Initial voltage , V: Final voltage, ln: Natural Log, C: Capacitance (Farads), R: Load Resistance
(i.e. A 1500uF capacitor charged at 125VDC is discharged to 30 V through a relay having coil resistance of 10 Ohm will take:
t = (10 Ohm)*(1500*10^-6 F)*ln (30/125) = 0.021 Sec (to discharge to 30V DC from 125VDC through 10 Ohm resistance).
Vo: Initial voltage , V: Final voltage, ln: Natural Log, C: Capacitance (Farads), R: Load Resistance
(i.e. A 1500uF capacitor charged at 125VDC is discharged to 30 V through a relay having coil resistance of 10 Ohm will take:
t = (10 Ohm)*(1500*10^-6 F)*ln (30/125) = 0.021 Sec (to discharge to 30V DC from 125VDC through 10 Ohm resistance).
Question: Can the CTD be used as a DC power supply?
Answer: The CTD is designed to be a source of DC power in the event of a power failure only. The energy stored is typically used to energize a coil and open a breaker or switch. It is not designed for continuous output. If a load is placed across the output terminals while the unit has an input voltage applied, the thermistor will gradually increase the resistance of the input side of the device and choke down the output voltage.
Question: How is the CTD typically installed when used for Shunt Trip Devices?
Answer: There are many different uses for the CTD. The most typical is using for emergency trip power with a shunt coil devise. The typical installation diagram is shown in figure 1.