WARNING using switcher power inverters in Dodge Ram Trucks and Ram Vans
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Joined: Dec 2005
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From: Nashville
RE: WARNING using switcher power inverters in Dodge Ram Trucks and Ram Vans
IGadget,
Yes, your answer would be true for a rated 10A circuit. Are the 1st generation Ram Vans like this? However, on the Ram Van 2nd Generation, the power outlet is rated at 20A while the ligher outlet is rated at 15A. Knowing the difference between both, I used the 20A outlet for the inverter.
I would have to concur with landyacht318 with the amount of power being drawn and the charge of the alternator barely dropping while under load. His alternator is basically similar above 130A.
All in all, my efforts were not looking at the AC hum or AC line for clean power. Rather, the objective was looking at the PWM and EMI harmonics that can be easily seen on a Tektronix Oscilloscope using PWM tracking probes.
Pulse width modulation, PWM, controlled inverters often use switching frequencies on the order of 10 kHz, much lower than what is normally considered "high frequency." However, the fundamental switching frequency and its harmonics can interfere with the operation of associated higher frequency circuits.
Common mode currents from the PWM controlled power fed to the inverter can couple through the capacitance and result in significant currents that flow in the metal structures of the vehicle. These currents can cause enough voltage drop in "ground" to affect other circuits. Such ground drops caused the common mode voltage on the balanced input to a high frequency device to exceed the device specifications. The result caused the circuit to malfunction.
The key to this problem is to either reduce the common mode currents or lower the ground impedance, which includes a significant resistive component at these low frequencies. One way to reduce common mode currents is to shield them. In my case, running the PWM inverter directly from the battery will require the use of heavy gauge wire with shielding that is in no way grounded to the vehicle.
Not all PWM inverters are the same either. Some of the more expensive PWM inverters use a harmonic suppression control circuit. However it may be, some of these suppression circuits are better than others.
Therefore there is a weakness in the Wal*Mart sold brand of inverter using the PWM switching which made a mess with the vehicle's electrical components.
Yes, your answer would be true for a rated 10A circuit. Are the 1st generation Ram Vans like this? However, on the Ram Van 2nd Generation, the power outlet is rated at 20A while the ligher outlet is rated at 15A. Knowing the difference between both, I used the 20A outlet for the inverter.
I would have to concur with landyacht318 with the amount of power being drawn and the charge of the alternator barely dropping while under load. His alternator is basically similar above 130A.
All in all, my efforts were not looking at the AC hum or AC line for clean power. Rather, the objective was looking at the PWM and EMI harmonics that can be easily seen on a Tektronix Oscilloscope using PWM tracking probes.
Pulse width modulation, PWM, controlled inverters often use switching frequencies on the order of 10 kHz, much lower than what is normally considered "high frequency." However, the fundamental switching frequency and its harmonics can interfere with the operation of associated higher frequency circuits.
Common mode currents from the PWM controlled power fed to the inverter can couple through the capacitance and result in significant currents that flow in the metal structures of the vehicle. These currents can cause enough voltage drop in "ground" to affect other circuits. Such ground drops caused the common mode voltage on the balanced input to a high frequency device to exceed the device specifications. The result caused the circuit to malfunction.
The key to this problem is to either reduce the common mode currents or lower the ground impedance, which includes a significant resistive component at these low frequencies. One way to reduce common mode currents is to shield them. In my case, running the PWM inverter directly from the battery will require the use of heavy gauge wire with shielding that is in no way grounded to the vehicle.
Not all PWM inverters are the same either. Some of the more expensive PWM inverters use a harmonic suppression control circuit. However it may be, some of these suppression circuits are better than others.
Therefore there is a weakness in the Wal*Mart sold brand of inverter using the PWM switching which made a mess with the vehicle's electrical components.
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RE: WARNING using switcher power inverters in Dodge Ram Trucks and Ram Vans
I have one of these in my truck and it's on 24/7. never had a problem with it. have run the laptop & cell charger (light draw) and have not had an issue.
I'll bet your drawing more than the 100W that the cig lighter/12v aux port can support, did you wire it directly to the battery as mentioned in the manual? (BTW, I didnt read all of the posts so if this was covered already, sorry).
I'll bet your drawing more than the 100W that the cig lighter/12v aux port can support, did you wire it directly to the battery as mentioned in the manual? (BTW, I didnt read all of the posts so if this was covered already, sorry).
