The following product line is being discontinued. Contact Power-io for a suitable replacement.

4-20mA activated, three phase, 25 or 35 amps per leg, din rail contactor
  • Accepts a 4-20mA analog process input and provides a high speed, time proportional AC output (TPO)
  • Permits a PLC, PC, DCS or other control system to supply a TPO without any software programming or intensive CPU calculations of variable on time vs off time.
  • Output cycle time ("ON" time + "OFF" time) = approximately 0.5 second at 50%. Output resolution is one half of one sinewave (8.3 msec for 60 hz applications).

For example, when the POWER-IO unit is used to control an electric heater, band heater, heat sealing bar, etc:
   4mA = 0% = heater is off
   12mA = 50% = heater is ON for 250 msec, OFF for 250 msec, ON for 250 msec...
   16mA = 75% = heater is ON for 375 msec, Off for 125 msec, ON for 375 msec...
   20mA = 100% = heater is ON
Note: Rapid pulsing of the heaters provides the most precise temperature control, PLUS it dramatically increases the life of the heaters due to a reduction in the thermal stress of expansion and contraction. Since the contactor is switching at the zero crossing mark of a sinewave, there is no electrical noise that might interfere with nearby electronics. Also, since the calculated ON or OFF time period is measured in half sine waves, the contactor will automatically adjust the total cycle time in order to maintain the best ratio of ON/OFF to match your control input.

Three phase, 25 or 35 amps per leg, din rail contactor


  • Maximum Surge Survival™ technology -- triple layer, voltage surge protection
  • Green LED for input status
  • Thermally optimized heat sink permits edge-to-edge installations on a din rail
  • Built-in snubber circuit
  • Zero crossing activation -- low EMI, low noise to nearby electronics
  • Internal 50A thyristors for high inrush capability
  • 4000 volt isolation, 1400Vpk blocking voltage
  • 1000 volt / microsecond immunity
  • Highest thermal efficiency -- less than 1.2 watts per amp switched, per leg
  • CE, UL recognized, CSA
  • Industry standard A1, A2, L1, T1, L2, T2, L3, T3 terminal numbers
  • High density design permits more amps per square inch
  • 3Ø = 25 amps per leg, 2Ø using L1/T1 and L3/T3 = 35 amps per leg.
  • Optional: 3 internal MOVs for a fourth layer of surge survival (models "5V")
DDA3 solid state contactor
DDA temperature curver

Part Numbers

DMA3-6V75T   up to 75 amps TOTAL; 25A on three legs or 35A on 2 legs; 660V max, 4-20mA analog input activated Buy

DMA3-5V75T   up to 75 amps TOTAL; 25A on three legs or 35A on 2 legs; 575V max; 3 internal MOVs; 4-20mA analog input activated. Non-standard model -- consult factory for price and availability.

DDA size
DDA size


Part Number Line Voltage Range (VAC) Load Current Range (A RMS) Max Voltage Drop @ 20mA
4-20mA analog input activated
DMA3-6V75T  24-660 .10-25 (3 leg) or 35 (2 leg) 10 VDC
DMA3-5V75T 24-575 .10-25 (3 leg) or 35 (2 leg) 10 VDC
Installation The DMA3 can be installed on a din rail or directly on a metal panel. The heat sink must be installed so the air flows up and through the fins.
Off-State dv/dt 1000 v/µs
Isolation 4000 volts isolation
I²T fuse 50A or less, for example: Bussman FWP50A14F, FWC32A10F, FWC20A10F. Ferraz B093910, M330015, K330013
Example of control 0% = heater or load is "off"
50% = heater "on" 250 mseconds, "off" 250 msec, "on" 250 msec...
75% = "on" 375 msec, "off" 125msec, "on" 375 msec....
85% = "on" 425 msec, "off" 75msec, "on" 425 msec....
100% = heater "on"
Turn-on time <8.3 ms at 60hz
Turn-off time <8.3 ms at 60hz
Power terminals Will accept #24-#10 AWG wire. Torque: 7-9 inch lbs.
Control terminals Will accept #24-#14 AWG wire. Torque: 4 inch lbs.
Internal MOVs The "5V" models have three internal MOVs installed providing a fourth layer of surge survivial. Using the MOVs limits the product to applications from 48 - 575 volts.
Terminology The word "leg" refers to a switched AC power line. A three phase application may use 3 switched lines or 2 switched lines.
Additional information

Close up photo of: three, din rail solid state contactors and their labels

Wiring examples of various 3 phase loads: 3 phase contactor wiring