In this video we’ll wrap up our quick look at the differences between the GS2 and GS20
drive families feature sets.
The GS20 has three outputs, two digital and one relay.
The GS2 has two Relay outputs.
The GS2’s second relay maps to the GS20’s Digital output 1.
So if you are using both relays on the GS2, you will need to make sure the GS20’s digital
output can handle the load.
The GS20 also has a pulsed digital output that can be used to monitor the drive’s
frequency or control other devices.
Both drives have one analog output, digital and analog inputs, and a 10-volt supply for
things like an external potentiometer.
Having two analog inputs is a big deal because you can now you can use that second analog
input to do summing, PID reference, offsets, all kinds of cool things.
The GS20 also has a 24-volt supply which can be used to power sensors up to 100 mA.
I love that the GS20 gives me two 24-volt terminals …
And remember that the GS20 uses these spring clamp terminals and the GS2 drives use screw
terminals which can handle wire gauges up to about 12-gauge.
So, make sure your existing wiring will fit in the smaller GS20 spring clamp terminals
which can take up to 18-gauge wire.
On the digital inputs the GS20 has a lot more options for controlling the drive.
The GS20 has an Up Down option feature where you press an up or down arrow to adjust the
frequency.
Some people refer to that as an electronic potentiometer.
You can even use a pulsed digital input to control the frequency of the drive.
That means you can now have a master drive output a pulse train – using that dedicated
pulsed output - that slave drives can use as a frequency source.
That gives you a much more reliable system because you don’t have to worry about analog
noise messing things up!
The GS20 also allows you to control the response time of the digital inputs and the polarity.
The digital outputs on the GS20 have a lot more options and you can control the polarity
of those too.
I really like that I can monitor the Digital I/O on the GS20 – being able to see what
the drive sees makes debugging my wiring so much easier.
The GS20 has a lot more analog input functions, and while both drives allow you to change
the Bias, Gain and polarity and monitor for signal loss, the GS20 also lets you filter
and sum the analog inputs and allows you to view the value of the analog input.
Again, it makes debugging analog inputs so much easier when you can see what the drive
sees.
Both drives have a potentiometer on the keypad, but the GS20 gives you more control over the
potentiometer value.
The GS20 also allows you to modify analog inputs using a 3-point curve.
I love this feature because it allows me to linearize my analog inputs which really helps
things like PID.
I can take a system response like this and use this curve function to turn it into a
more linear response like this which makes PID much more stable and accurate.
The user manual has a bunch of examples that show you step by step how to use analog inputs.
The GS20 has a lot more analog output functions, plus you can modify the Gain, Bias and the
polarity of the analog outputs and you can monitor the value of the analog output – again
making system debug so much easier when you can actually see what the drive thinks it
is sending out.
Both drive families provide 0-10 volt analog outputs, but the GS20 can also output 0 to
20 and 4 to 20 mA. and the GS20 is a 10bit analog output, while the GS2 is only 8 bits.
Both drives have multistep where you specify a table of frequencies you want the drive
to use and select the frequency you want from that table using digital inputs, but the GS20
has twice as many available steps.
The multistep group also has 19 buffer registers for the PLC to use.
That has nothing to do with multistep, it’s just where they ended up.
Remember, you have two ways to talk to the built-in PLC.
You can talk directly to the drive and directly to the drives built-in PLC via Modbus RTU,
but that requires that your system keeps track of two ModBus devices in the same device – which
can get confusing for your system.
Or you can have your external device talk only to the Drive and read and write to the
buffer registers.
The PLC then monitors and updates those.
That keeps things much simpler for your system because your system thinks it is only talking
to the drive and knows nothing about the PLC which most of the time is just acting as a
co-processor augmenting the Drive’s functionality.
If you are using Modbus TCP or EtherNet/IP then you have to use this method because those
two can’t talk directly to the PLC.
You can also use the buffer registers to collect random parameters into a sequential bock of
parameters.
Now you can access them with a single Modbus command instead of issuing a separate Modbus
command for each parameter.
That saves you a lot of communications bandwidth.
This is the same function as a GS2 Block Transfer.
Let’s do the PID section next because it relies heavily this I/O. Your current GS2
PID numbers will transfer directly over to the GS20 because the default GS20 configuration
uses the same dependent PID algorithm.
But the GS20 also has the option of using the Parallel or independent form of the equation
which is nice because you can tune each coefficient independently.
Both can detect loss of feedback signal, but the GS20 can also detect when the deviation
between the setpoint and process variable is out of bounds.
The GS20 also has Sleep mode which is great for things like tank filling applications
where PID doesn’t need to run once the tank is full.
The GS20 can also prevent PID from forcing the output to an undesired direction and can
slow down the rate of the setpoint – this is especially helpful when the setpoint comes
in over coms or multi-setpoint so you don’t get an instantaneous change that PID has to
react to.
The GS20 Drives can take care of that for you automatically.
The GS20 has a lot more setpoint and process variable sources and a whole bunch more features
that we will cover in the dedicated PID tutorial Videos.
The SPECIAL group has DC Braking, Controls how the GS20 deals with momentary power loss,
and has DEB to intelligently manage deceleration when there is a power loss.
There is a whole video dedicated to that topic.
The GS20 allows you to control the operation of the fan to better optimize cooling and
maintenance for your application.
The GS20 has an energy savings mode which backs off on the output voltage once a system
is up and running and the torque is no longer required.
This works really well when you have loads that aren’t fluctuating or operating near
full load.
The GS20 has automatic voltage regulation which limits the output voltage when the input
voltage exceeds the motors rated voltage.
That prevents intermittent input voltage surges from heating up and damaging your motor over
time.
The GS20 also has lots of torque and slip tuning parameters which will be covered in
other videos.
And it has a function that detects when a load is out of balance, so the motor speed
can automatically be adjusted to keep the washing machine or mixing machine from thrashing
about due to un-even loads.
The communications setup is straight forward but of course the GS20 has a lot more options.
Protections are also very similar, but again, the GS20 has a lot more options, including
the ability to monitor an external thermistor, IGBT temperature monitoring, and Safe Torque
off which shuts down he drive completely independently of anything going on inside the drive.
That’s a huge safety feature that you just won’t find on drives in this price range.
The GS20 also has phase loss and low current detection – something else a lot of low
end drives can’t do.
It also has Fire mode and a bunch more protections the GS2 doesn’t have.
The Speed Control Group has all the parameters you will need to setup the fancy speed modes
that the GS2 doesn’t have and the Advanced group has the parameters for setting up the
Adjustable Speed Regulation, Torque mode, and PWM mode.
We will be covering all of those control modes in separate videos so I’m not going to dwell
on them there.
Finally, there is a Macro group where you can simply select the application you have
and the GS20 will auto populate the appropriate parameters with proper values.
This is a great way to get started quickly.
Start out with one of these presets and add your motors nameplate information.
It takes a lot of the anxiety out of getting the drive up and running quickly for common
applications.
The parameters used are listed in the user manual, so you can see exactly the kinds of
things you need to be thinking about for each application type.
That ought to be more than enough to give you a feel for the main differences between
the GS2 and GS20 drive families and what a huge value the GS20 is.
It might seem crazy that the GS20 can deliver all of this at a lower price and smaller footprint.
But when you realize the GS2 has been building its reputation as an industry staple for two
decades, and you realize how much microelectronics have changed over that time, well, yeah, it
makes sense that the GS20 can do a lot more for less cost and size.
Be sure to check out the GS20 quick start video.
There are a number of things in there that will help you get up and running quickly.
Meanwhile…
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