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Thanks for the replies. Vehicle will not be grounded when moving but will be grounded when stationary because it will power off vehicle loads which they may or may not be grounded. The design of the 3-phase generator has two possibilities, keep the neutral floating inside or bring it out and...

A 3-phase AC generator is mounted in a vehicle, say a truck and it is driven by the engine through a power take off. This generator provides power for the vehicle but it also can export power to external loads which can be grounded. The vehicle is metallic and it is required to be grounded as...

Agreed with Waross, if the power neutral is floating then ground fault should not trip out the generator. Suggest checking to isolate the problem: 1. Is there a line to line short, possibly a failed washer motor? 2. Is the PMS faulty or its sensors are faulty? 3. Is there any other possible...

ctpt, MOV's are for surge, voltage spikes or transient voltage protection. They are not adequate to protect overvoltages (swells) that are longer e.g. >1ms. The peak current ratings are usually for short duration spikes of 8 x 20us or 10 x 1000us. These spikes are generally cause by lightning...

Solar cells are rated in mA and Volts or Watts. Batteries are rated for energy storage capacity in mAh. It is an odd unit, because it is current output x time. I wonder why Joules is not used instead. Engineers and scientist learn about Joules in physics. The utility folks use kW hour. It...

rodeman, First of all: "mAh" means it is the current output for a period of time in hours. 100mAh will output 100mA for 1 hour. Your fan uses two AA batteries which means it adds up to 3.0V. I would guess that you'd need more mAh to get that motor to spin. AA batteries can put out a lot of...

According to a table in "Printed Circuit Board Design Techniques for EMC Compliane", spacing for 2,000Vrms is 8.4 mm [0.33"] and 5,000 Vrms is 17.5mm [.69"]. Your case the spacing is between these two. The Hipot voltage is determined usually by adding more voltage on top of the normal...

Thanks to all for informative replies. I thought to neglect radiation only because the busbar will have low resistance and would generate low heat. Here's some specifics if somebody wants to take a crack at calculations: Dimensions: L = 20" x 1" by 0.25" Heat Dissipation: 13 Watts It will be in...

Thanks, I did a google and found some answers too. http://www.engineersedge.com/heat_transfer/convection.htm The convection coefficient used is 18 BTU/hr*ft^2*F. The Area is the surface area, in this case the busbar. In this case, the temperature rise works out to about 5 C from ambient. I...

Thanks. So, in other words, the expression should be: Q = h_c*area*(Ta - T)? Is there a typical h_c coefficient or is there a reference somewhere? What is "area" supposed to be?

I have busbars that carry current and I want to do a rough order of magnitude calculation of the temperature of the busbar without measuring it [or using any thermal software]. Does anyone know how to do this? The following variables are known: 1. Ambient temperature, say Ta 2. Surface area...

morke, Rereading your post again, I think the cap is just for filtering and does not really contribute much to the arcing. It may be that the arcing was always an issue and the reason for the fried coil. You could try using an MOV [metal oxide varistors] ones rated for 250VAC - 500VAC...

morke, The voltage generated across the inductor is V = L x dI/dt where L = inductance of coil, dI/dt is the rate of rise for the current. In other words, the steeper the change in current the bigger the voltage which would cause arcing. The other thing: coils and latches usually have iron...

I used to design surge protectors with MOVs for massive computer market. MOVs are only good for spikes and cannot tolerate sustained overvoltage. They can be rated for fairly high peak current e.g.250kA but one should note that it is for a spike of say 8us x 20us or 10us x 1000us. Based on...

All the pwm does is effectively average the voltage across the motor. I think you are confusing duty cycle with frequency modulation. Pulse width modulation is varying the width of the ON pulses (duty) but keep the frequency constant (or period constant). If you are lowering the frequency to...

Another issue that you may have: PM DC motors typically have high rpm to operate optimally. Gear reducers are used to get more torque at low rpm.

The problem is that a MOSFET is not a very good linear device. An NPN transistor would be best but you might have a hard time finding one that can handle 50A. I would suggest a better way but not as simple: Switch the MOSFET gate with pwm. Put a current sensor in line with the MOSFET, feed...

Depends on the way the controller reads and interprets the temperature. Some have compensation to correct the non-linearity. Thermistor resistance are non-linear over temperature range and that is probably why the range is limited. I think it'd work but there might be small errors.

rab, You problem is vague. I'm assuming that you have -12V but the amp needs something like +12V? One possibility is to use an optoisolator?

Another possibility may be that your motor is too big for the IC. What's the HP or Wattage of the motor? According to the datasheet, your motor is reaching the limit of 0.7A. May be you can start it up slowly at low speed and increase the speed once it gets going. But, if you even can't get...