Test of Chinese Precipitator Supply
Posted: Tue Nov 14, 2017 6:07 am
All,
There has beeen a lot of speculation about the Chinese Precipitator Power Supply's, so with my new power load at hand, I decided to have a go at testing one of said supplies.
I work with Precipitators on the side, and to my embarrasment, my boss demanded that we also test these cheap supplies, so he bought a couple of these small 200W 30kV types.
This is the setup, where I run the ground wire through the 10A fuse of a multimeter, to monitor current, and load the supply with the full 1.6Mohm of the load, while monitoring the voltage of the output with a 20000:1 voltage probe, as well as monitoring the primary current with a Tek. P6021/134 current monitor.
The supply has 3 trimmers that controll voltage and current.
The voltage is regulated with 2 pots, where the one of them sweeps the output through the range, the other is a kind of bias pot, to the effect that in one extreme, the output is adjustable from 0-10kV, in the other extreme from 4-18kV. These numbers are with the 1.6Mohm load. With a proper 4Mohm load, I am sure it would regulate up to 30kV as advertised.
The current controll is designed to turn the supply off in the case of an arc, so when it is exeeded, the supply shuts down and comes up again after about one second.
I would warn against testing this kind of supplies without a load, as the field controll is really poor, and an arcover is a disaster just waiting to happen. The tell tale of this about to happen is a fierce hissing of corona, and this happens around 20kV, if you continue to turn the voltage up beyond that level, with the wires dangling, an arcover to the core is just around the corner. A punctured insulation just where the wire exits the coil potting, with surface tracking to the core, leading to a carbonized track is impossible to repair, so don't.
I tried this early in my career, so not this time, but I heard the corona, so be warned, it _will_ happen.
The resistance of the load is really too low for the supply, and this means that it cannot reach full voltage at full power, so the maximum output recorded was 18kV 12mA, not so shappy. It will deliver this effortlessly, I had it on the load for 10 minutes, and there was only a 15deg. temperature rize on the heatsink.
At full load, the switching frequency is down to 36kHz. The transformers are run in antiphase, so the output ripple is double that frequency, and quite large, as expected from this topology.
Turned down, the voltage is now 4kV, switching frequency up to 74kHz. There is a trimming pot. on the board that allows the voltage to be turned all the way down, but this than has the effect, that the maximum voltage is also lowered, to around 10kV.
I have not yet the possibility to test this kind of supply on a fusor, so I cannot say that they are, or are not suitable for the task.
I miss a dedicated current regulation, and the biggest challenge will be to route a voltage higher than 20kV to the fusor, instead of to the transformer core.
I think this would be an excellent supply for a demo fusor, and at 73 USD, you can hardly loose.
https://www.ebay.com/itm/300w-30kv-High ... 0005.m1851
Hope this helps,
Cheers, Finn Hammer
There has beeen a lot of speculation about the Chinese Precipitator Power Supply's, so with my new power load at hand, I decided to have a go at testing one of said supplies.
I work with Precipitators on the side, and to my embarrasment, my boss demanded that we also test these cheap supplies, so he bought a couple of these small 200W 30kV types.
This is the setup, where I run the ground wire through the 10A fuse of a multimeter, to monitor current, and load the supply with the full 1.6Mohm of the load, while monitoring the voltage of the output with a 20000:1 voltage probe, as well as monitoring the primary current with a Tek. P6021/134 current monitor.
The supply has 3 trimmers that controll voltage and current.
The voltage is regulated with 2 pots, where the one of them sweeps the output through the range, the other is a kind of bias pot, to the effect that in one extreme, the output is adjustable from 0-10kV, in the other extreme from 4-18kV. These numbers are with the 1.6Mohm load. With a proper 4Mohm load, I am sure it would regulate up to 30kV as advertised.
The current controll is designed to turn the supply off in the case of an arc, so when it is exeeded, the supply shuts down and comes up again after about one second.
I would warn against testing this kind of supplies without a load, as the field controll is really poor, and an arcover is a disaster just waiting to happen. The tell tale of this about to happen is a fierce hissing of corona, and this happens around 20kV, if you continue to turn the voltage up beyond that level, with the wires dangling, an arcover to the core is just around the corner. A punctured insulation just where the wire exits the coil potting, with surface tracking to the core, leading to a carbonized track is impossible to repair, so don't.
I tried this early in my career, so not this time, but I heard the corona, so be warned, it _will_ happen.
The resistance of the load is really too low for the supply, and this means that it cannot reach full voltage at full power, so the maximum output recorded was 18kV 12mA, not so shappy. It will deliver this effortlessly, I had it on the load for 10 minutes, and there was only a 15deg. temperature rize on the heatsink.
At full load, the switching frequency is down to 36kHz. The transformers are run in antiphase, so the output ripple is double that frequency, and quite large, as expected from this topology.
Turned down, the voltage is now 4kV, switching frequency up to 74kHz. There is a trimming pot. on the board that allows the voltage to be turned all the way down, but this than has the effect, that the maximum voltage is also lowered, to around 10kV.
I have not yet the possibility to test this kind of supply on a fusor, so I cannot say that they are, or are not suitable for the task.
I miss a dedicated current regulation, and the biggest challenge will be to route a voltage higher than 20kV to the fusor, instead of to the transformer core.
I think this would be an excellent supply for a demo fusor, and at 73 USD, you can hardly loose.
https://www.ebay.com/itm/300w-30kv-High ... 0005.m1851
Hope this helps,
Cheers, Finn Hammer