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Reading another thread got me thinking...
If the PJ inverter will operate much more "clean" at 32V, but I have a 36V asl6.5 transformer, is there any reason I couldn't add a few more turns to my 240V secondary and then decrease the output of the inverter via the front panel adjustment? I haven't done the math yet as to how much wire is actually required, but the way I have my transformer setup (external) it wouldn't be too difficult to add a few more wraps...
Reading another thread got me thinking...
The inverter actually regulates from the output voltage, so even if you adjust the transformer ratio, the output voltage will (should!) remain the same.
What is worth keeping in mind is the required headroom for a pure sine output...in overly simplified math, you will need (transformer voltage * square root of (2)) in DC voltage in order to reach the top of a sine wave. For 36v * 1.414 = 50.9v, not accounting for any other losses (transformer, wires, FETs).
It is easy to determine the number of turns required to adjust the voltage by a certain amount. With the inverter running, set your meter for AC volts, put one meter probe through the center of the transformer core, and then short both meter probes together. PJ transformers typically range from 0.7v - 1.5v. This is the turns/volt; you can only adjust the voltage in multiples of this number.
If the PJ inverter will operate much more "clean" at 32V, but I have a 36V asl6.5 transformer, is there any reason I couldn't add a few more turns to my 240V secondary
The 32vac is the primary input to the transformer and can not be converted from 36vac by adding winding to secondary . Adding more turns to the secondary L2 is to increase the voltage to match the L1 ac voltage . Powerjack design some ASL6.5 transformer 30 vac which is better for 48v dc lithium iron phosphate battery and now the ASL6.5 is 36vac . My ASL9.0 36vac is now running 60v dc lithium ion battery string and the sine wave is good to 54 v dc battery input . 36vac transformer need higher dc battery input voltage to keep the pure sine wave for inductive load . 16s lithium ion at 66 vdc make the transformer run hot so the max is 62 vdc for ASL9.0 transformer .
The 32vac is the primary input to the transformer and can not be converted from 36vac by adding winding to secondary .
Here I will disagree. What is being changed is the transformer ratio, regardless of whether the turns are added to the secondary, or removed from the primary.
There is a difference however; adding more turns to the secondary uses more wire, which is why it generally isn't done. It does decrease the turns/volt core voltage, which may hypothetically provide more safety range before core saturation (which is when FETs go kaboom.)
However, removing turns from the primary will increase the turns/volt (if driven to the same AC input voltage)...and if this exceeds the transformer core's saturation voltage, the no-load current will start to rise (as well as transformer heat), AND reduced efficiency.
16s lithium ion at 66 vdc make the transformer run hot so the max is 62 vdc for ASL9.0 transformer .
Betcha this is due to a lack of ferrite chokes on the transformer primary wires. These chokes serve to absorb the 24KHz SPWM carrier, as it just gets "burned up" in the big transformer if not filtered out. If the big transformer is getting the 24KHz SPWM carrier, it'll get hot.
In my experience, the more ferrite choke filtration on the transformer primary wires, the higher the DC input voltage you can run...without the no-load current going up excessively. Conversely, the less the ferrite choke filtration on the transformer primary wires, the sooner you'll notice high no-load currents & heat.
PJ seems to provide one ferrite choke on their inverters...and always with just a single turn of transformer primary wire through it. In my experience, the best performance is found with 2 full turns of transformer primary wire through the ferrite. Adding a second ferrite choke to the other transformer primary leg (with 2 turns) helps with higher battery voltages.
What is being changed is the transformer ratio, regardless of whether the turns are added to the secondary, or removed from the primary.
I do not know how to change a 36vac powerjack transformer to a 32vac transformer like the GS 32vac transformer . I think a 36vac transformer is design that way and need to change the primary winding and secondary winding according to a formula to make it into a 32vac transformer . That is a lot of work to rewind a new transformer . Powerjack transformer for L1 N L2 is a design problem and not easy to fix .
I do not know how to change a 36vac powerjack transformer to a 32vac transformer like the GS 32vac transformer . I think a 36vac transformer is design that way and need to change the primary winding and secondary winding according to a formula to make it into a 32vac transformer . That is a lot of work to rewind a new transformer . Powerjack transformer for L1 N L2 is a design problem and not easy to fix .
Easiest way to change a PJ transformer spec from 36v to 32v...is to remove several turns of wire from the primary winding (which is on the outside anyway). Having a variac on your bench is extremely handy for working with transformers. There is no need to adjust the secondary winding.
The number of turns on the secondary winding is dependent on the turns/volt, which is dependent on the core. Secondary imbalance is due to the winding specification not being matched; adding a few turns to the "low" coil is relatively trivial.
HOWEVER: It is worth noting that reducing the primary voltage specification on a PJ transformer, begins to run the risk of saturating the core with huge surge loads. If the core saturates, the FETs go. This is probably part of why PJ runs a rather high transformer ratio to begin with, as it reduces the risk of transformer core saturation at lower battery nominal voltages.
It is worth noting that reducing the primary voltage specification on a PJ transformer, begins to run the risk of saturating the core with huge surge loads
Will your GS inverter with 32vac primary transformer still have a pure sine wave when battery voltage drop to 45v dc ? The GS inverter seem to be able to run at 66v dc battery voltage also . Changing powerjack transformer primary input to 32vac will probably not make much different because it is design different from the GS transformer . I have a variac but probably not going to modify the powerjack transformer . Adding the choke is very useful . Thank you .
Will your GS inverter with 32vac primary transformer still have a pure sine wave when battery voltage drop to 45v dc ?
At no load, 45.25v is the theoretical minimum for a pure sine wave, yes. Under load, this minimum voltage requirement will rise.
The GS inverter seem to be able to run at 66v dc battery voltage also
Yes, because of the dual ferrite chokes on the transformer primary lines. Otherwise it'd start to struggle pretty badly up there.