The new SSRTC mounts directly on the input terminals of a Solid State Relay and provides a low cost, conveniently packaged temperature control solution. The input accepts J or K type thermocouples and can be used on heat or cool processes with on/off or proportional control. The setpoint can be controlled by a potentiometer or analog voltage or analog current. The temperature setpoint is proportional to the voltage or current at the setpoint input. Status indicators indicate how close the temperature is to the setpoint.
We get many calls from customers that want to control the temperature of a process without a closed loop temperature controller. In this mini article we will briefly discuss open loop temperature control vs closed loop temperature control. First, lets simply define closed loop and open loop as it applies to common electrically heated processes:
Close loop temperature control utilizes a temperature sensor that monitors the process. This feedback is fed to a temperature controller which controls a Power Controller that will apply power to the heater precisely and maintain the process temperature. Some of the advantages of closed loop control are accuracy, repeatability, fast warmup times and fast recovery times.
Open loop temperature control does not utilize temperature feedback from the process. The power delivered to the heater is set by the user, usually with a potentiometer and SCR Power Controller or a Variac (variable auto transformer). Some of the advantages of open loop control are simplicity, low cost, reliability.
One of the major advantages of NuWave SCR Power Controllers and SSR Driver Boards is line voltage compensation. Line voltage compensation corrects for changes in line voltage. Performance improvements can be observed in closed loop processes, but especially in open loop processes.
If you have a process where the temperature accuracy is not critical, open loop control may be an option. The only way to really tell if open loop control is suitable is to try it in your process and see if the results are acceptable.
The new SSRMON2 mounts to a Solid State Relay and provides load break protection as well as monitoring the SSR for failure. The SSRMON2 can be wired for interrupted mode or continuous mode. Interrupted mode forces the SSR off periodically to test the input to output logic. The SSRMON2 operates on 12 or 24VDC and can be used on line voltages from 100-600VAC .
The new 1P-CL-N SCR power control offers features only found in much more expensive power controllers. The compact package can control up to 80Amps at 40C and offers current feedback. The current is sensed using an external current transformer and is used to limit the current on inductive loads such as transformers or resistive loads that have a sharp positive temperature coefficient such as quartz heaters or molybdenum heaters. Reliable firing / commutation of inductive loads are no problem with the on-board rugged SCR snubber.
The SSRMAN-1LP 4-20 mA Solid State Relay driver provides 0-100% PWM of any standard SSR. The PWM cycle time of the time proportioning is 350mS at the center but gets longer toward the end of the range to optimize the resolution of the output of the 4-20 solid state relay system. The calibration of the time proportioning converter can be adjusted by ordering option -ZS (zero and span pots). The SSRMAN-1LP can drive up to 4.2V @ 14mA offering a high performance, low cost solution to 4-20mA SSR systems.
The Staging Control with Verneir – NWVS is a step controller that provides modulation in multi-stage applications such as duct heaters. The built in 0-10V Vernier stage output allows for smooth, precision control of the load. When the verneir output is connected to an SSR or Phase Angle Controller – SSRMAN-1P it will increase the precison of the heat control without reducing the life of the system contactors. The unit’s LEDs show the power and output status of all of the stages including the vernier output.
Most current transformers suffer from severely inaccurate measurements of the load current in phase angle controlled loads. This is because they tend to respond mainly to the peaks of the signal which have little to do with the actual current present in the load circuit. A true RMS analysis of the current waveform is required to get an accurate value.
Our RMS Current transformer – NWCT is a True RMS current transducer that can be ordered as 0-10V or 4-20mA output. The output is proportional to the current in the conductor passed through the sense transformer. The advantage to the NWCT is that it can sense distorted sinusoidal signals such as phase control and provide a True RMS output of the signal. The NWCT Current Transformer uses the latest in signal processing technologies to provide true RMS 4-20mA or 0-10V output of distorted AC current signals such as phase angle controlled loads.
Our new small temperature controller – MicroTC is our smallest and lowest cost temperature controller. The MicroTC is factory set for your setpoints and hysteresis. A version is available with setpoint adjustment from an external potentiometer. The small MicroTC is available in 12V and 24V versions and provides a 3 Amp MOSFET output that can be used to drive an SSR ( solid state relay) or small heater. The integral small solid state temperature sensor eliminates the cost of an external thermocouple or RTD.
Introducing the new RCSB RC snubber board for Solid State Relays SSRs.
The RCSB snubbersuppresses dV/dt and provide reliable commutation. This is especially important when controlling transformer coupled loads as improper commutation can result in huge inrush currents and blown fuses. The RCSB snubber is also used on our SCR power control assemblies. The RCSB is available in 120, 240, 480 and 600VAC versions.
The RCSB Snubber Board mounts directly on the output terminals of a solid state relay. The RCSB provides overvoltage protection from transients and limits dV/dt.
For more information: SSR Snubber Network
The new SSR Mounted Phase Angle Controller Module SSRMAN-1P-CL mounts directly on the SSR input terminals and provides true linear power phase angle control of the load. The output power is based on the command input and the current feedback from the current transformer. The command can be dip switch selected from over seven different industry standard inputs. Using the SSRMAN-1P-CL with the appropriate SSR for your load will provide a modular high isolation SCR power control at a very low price. An extensive filtering scheme and proprietary zero cross detection algorithm improves noise rejection without sacrificing accuracy.