engineering data sheet u*d relay - nonlatch 2 pdt, 4 amp application notes: 001 007 applicable socket: 081a24 polarized, non latching hermetically sealed relay contact arrangement 2 pdt coil supply direct current meets the requirements of mil-prf-5757 nfc45255 ya708a principle technical characteristics contacts rated at 4 amps / 28 vdc weight 18 grams max dimensions of case 20.5mm x 23mm x 9.2mm hermetically sealed, corrosion protected metal can. contact electrical characteristic minimum operating cycles contact rating per pole and load type load current in amps @28vdc 100,000 cycles 500,000 cycles resistive load low level (30a/30mv) 4 - leach ? international solutions for power switching and control www.leachintl.com north america 6900 orangethorpe ave. p.o. box 5032 buena park, ca 90622 usa tel: (01) 714-736-7599 fax: (01) 714-670-1145 europe, sa 2 rue goethe 57430 sarralbe france tel: (33) 3 87 97 98 97 fax: (33) 3 87 97 84 04 asia-pacific ltd. 20/f shing hing commercial bldg. 21-27 wing kut street central, hong kong tel: (852) 2 191 2886 fax: (852) 2 389 5803 date of issue: 10/05 - 45 - page 1 of 4
coil characteristics (vdc) u*d code 06 12 28 48 75 120 nominal operating voltage 6 12 28 48 75 120 maximum operating voltage 7 14 30 55 85 135 guaranteed pick-up voltage at +125 c 5 10 21 40 60 100 guaranteed drop-out voltage at -65 c 0.4 0.8 1 2.9 4.5 6.9 coil resistance in w 15% at +25 c 31 126 575 1800 4400 12700 general characteristics temperature range -65c to +125c dielectric strength at sea level - contacts to ground 500 vrms / 50 hz - between contacts 500 vrms / 50 hz dielectric strength at altitude 25,000 m (all points) 250 vrms / 50 hz initial insulation resistance at 100 vdc > 1000 m w sinusoidal vibration (except mounting styles p,t: 20 g) 30 g / 70 to 3000 hz shock 100 g / 6 ms maximum contact opening time under vibration and shock 10 s operate time at nominal voltage (including bounce) 5.5 ms max release time at nominal voltage (including bounce) 5.5 ms max contact resistance at 0.1 amp - initial value 35 w max - after life 55 w max date of issue: 10/05 - 46 - page 2 of 4
mounting styles u*d dimensions in mm tolerances unless otherwise specified 0.25mm terminal types date of issue: 10/05 - 47 - page 3 of 4
schematic diagram u*d numbering system u f d c 28 basic series designation__________________________| | | | | 1-terminal types (s,f,a,t)_____________________________| | | | 2-non latching (d)_________________________________________| | | 3-mounting style (c,b,e,p,g,k,t)_______________________________| | 4-coil voltage (06,12,28,48,75,120)_________________________________| notes 1. isolation spacer pads for pcb mounting available on request. 2. for other mounting styles or terminal types, please contact the factory. typical characteristics l coil resistance/temperature change: see application note no. 001 l coil l/r ratio = 1.5 ms date of issue: 10/05 - 48 - page 4 of 4
application notes n001 correction due to coil copper wire resistance change in temperature example: coil resistance at 25c: 935 ohms. what is it at 125c? correction coefficient on diagram is: 1.39 at 125c. r becomes: 935x1.39=1299 ohms correction also applies to operating voltages date of issue: 6/00 - 1 - page 1 of 1
application notes n007 suppressor devices for relay coils the inductive nature of relay coils allows them to create magnetic forces which are converted to mechanical movements to operate contact systems. when voltage is applied to a coil, the resulting current generates a magnetic flux, creating mechanical work. upon deenergizing the coil, the collapasing magnetic field induces a reverse voltage (also known as back emf) which tends to maintain current flow in the coil. the induced voltage level mainly depends on the duration of the deenergization. the faster the switch-off, the higher the induced voltage. all coil suppression networks are based on a reduction of speed of current decay. this reduction may also slow down the opening of contacts, adversly effecting contact life and reliability. therefore, it is very important to have a clear understanding of these phenomena when designing a coil suppression circuitry. typical coil characteristics on the graph below, the upper record shows the contacts state. (high level no contacts closed, low level nc contacts closed, intermediate state contact transfer). the lower record shows the voltage across the coil when the current is switched off by another relay contact. the surge voltage is limited to -300v by the arc generated across contact poles. discharge duration is about 200 mircoseconds after which the current change does not generate sufficient voltage. the voltage decreases to the point where the contacts start to move, at this time, the voltage increases due to the energy contained in the no contact springs. the voltage decreases again during transfer, and increases once more when the magnetic circuit is closed on permanent magnet. operating times are as follows: time to start the movement 1.5ms total motion time 2.3ms transfer time 1.4ms contact state date of issue: 6/00 - 8 - page 1 of 4
types of suppressors: passive devices. the resistor capacitor circuit it eliminates the power dissipation problem, as well as fast voltage rises. with a proper match between coil and resistor, approximate capacitance value can be calculated from: c = 0.02xt/r, where t = operating time in milliseconds r = coil resistance in kiloohms c = capacitance in microfarads the series resistor must be between 0.5 and 1 times the coil resistance. special consideration must be taken for the capacitor inrush current in the case of a low resistance coil. the record shown opposite is performed on the same relay as above. the operation time becomes: - time to start the movement 2.3ms - transfer time 1.2ms the major difficulty comes from the capacitor volume. in our example of a relay with a 290 w coil and time delay of 8 ms, a capacitance value of c=0.5 uf is found. this non polarized capacitor, with a voltage of 63v minimum, has a volume of about 1cm 3 . for 150v, this volume becomes 1.5 cm 3 . date of issue: 6/00 - 9 - page 2 of 4
the bifilar coil the principle is to wind on the magnetic circuit of the main coil a second coil shorted on itself. by a proper adaptation of the internal resistance of this second coil it is possible to find an acceptable equilibrium between surge voltage and reduction of the opening speed. to be efficient at fast voltage changes, the coupling of two coils must be perfect. this implies embedded windings. the volume occupied by the second coil reduces the efficiency of the main coil and results in higher coil power consumption. this method cannot be applied efficiently to products not specifically designed for this purpose. the resistor (parallel with the coil) for efficient action, the resistor must be of the same order of magnitude as the coil resistance. a resistor 1.5 times the coil resistance will limit the surge to 1.5 times the supply voltage. release time and opening speed are moderately affected. the major problem is the extra power dissipated. semi-conductor devices the diode it is the most simple method to totally suppress the surge voltage. it has the major disadvantage of the higher reduction of contact opening speed. this is due to the total recycling, through the diode, of the energy contained in the coil itself. the following measurement is performed once again on the same relay. operation times are given by the upper curve: - time to start the movement 14ms - transfer time 5ms these times are multiplied by a coefficient from 4 to 8. the lower curve shows the coil current. the increase prior to no contact opening indicates that the contact spring dissipates its energy. at the opening time the current becomes constant as a result of practically zero opening speed. due to this kind of behavior, this type of suppression must be avoided for power relays. for small relays which have to switch low currents of less than 0.2 a, degradation of life is not that significant and the method may be acceptable. date of issue: 6/00 - 10 - page 3 of 4
the diode + resistor network it eliminates the inconvenience of the resistor alone, explained above, and it limits the action of a single diode. it is now preferred to used the diode + zener network. the diode + zener network like the resistor, the zener allows a faster decurrent decay. in addition it introduces a threshold level for current conduction which avoids the recycling of energy released during contact movement. the lower curve on the opposite record demonstrates those characteristics. voltage limitation occurs at 42v. the two voltages spikes generated by internal movement are at lower levels than zener conduction. as a result, no current is recycled in the coil. the opening time phases are as follows: - time to start the movement 2.6ms - total motion time 2.4ms - transfer time 1.4ms the release time is slightly increased. the contacts' opening speed remains unchanged. date of issue: 6/00 - 11 - page 4 of 4
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