Showing posts with label load. Show all posts
Showing posts with label load. Show all posts
Thursday, October 6, 2016
Testing Alternator Current using Dummy Load
Testing Alternator Current using Dummy Load
The post explains a method of checking or verifying alternator maximum current delivering capacity using a shunt regulator as the dummy load and an ammeter. The idea was inquired by Mr. Joe.
Question
Hi Sir,
I need help designing an electronic dummy load that can handle high enough power from motorcycle alternator. I need to know how much power is available from the alternator because when I first time finished rewound the alternator, it shows me 7A of power from two winding set (my alternator is modified by adding another winding on outer layer of existing winding). But now it only shows about 4A of power from the two winding set. Is it best to use electronic dummy load or just simple resistive load as resistive load is only work in certain voltage range (thats what I know) to test the alternator.Question
Hi Sir,
Kindly need your help for the circuit design.
My Reply
Hi Joe, did you try using your digital mulltimeter with a shunt regulator. You can set the meter to the maximum current range, normally this could be at 20Amp AC range and check the results by connecting its prods at the output of the shunt regulator and input of the shunt with the alternator winding output. This should provide you with the necessary information??
The Design
I have already discussed a simple shunt regulator circuit in one of my earlier posts, we can implement the same shunt regulator circuit as a dummy load for the proposed testing of alternator current, through an ammeter in series with the shunt device.
Although an ammeter can be directly connected with the alternator output for measuring its current capacity, a shunt regulator ensures a controlled measurement of the measurement over a specified voltage limit.
Meaning if the alternator is rated to generate a fluctuating voltage say from12V to 24v, the shunt regulator could be set to dump the excess voltage above 12V and control the alternator voltage at this level.
However for the meter this might have no notable effect except a little stress-free working due to the controlled voltage level.
The following circuit shows how to use a shunt regulator as a dummy load with a ammeter for testing alternator current safely and accurately.
Available link for download
Sunday, September 11, 2016
Over Voltage Protection Circuit for Automotive Load Dump
Over Voltage Protection Circuit for Automotive Load Dump
Transient bus voltages are a significant risk factor to integrated circuits. The maximum breakdown voltage that an integrated circuit may be specified to tolerate is determined by its style and design approach that can be predominantly low for tiny CMOS devices.
Transient or repetitive over voltage circumstances that defeat an IC‘s absolute highest voltage spec may possibly irreversibly harm a device.
The necessity for over voltage safety is notably prevalent in automobile 12V and 24V designs in which peak "load dump" transients is usually as very high as GOV. Certain load safeguarding strategies shunt input transient to ground through devices similar to avalanche diodes and MOVs.
The difficulty with the shunt method is that a great deal of power could possibly end up being processed.
Shunt techniques are usually undesirable should there be an obligation to render continual protection throughout an over voltage situation (as transpires with dual battery).
The Over Voltage Protection Circuit for Automotive Load Dump shown in Figure 1 is a perfect series-disconnect or series cut-of circuit which has been built to safeguard a switching regulator load that possessed an optimum input voltage of 24V.
The circuit is intended from economical discrete devices and makes use of a single Texas Instruments LMV431AIMF.
Given that this circuit employs a PFET pass device (Q1), there may be a marginal forward voltage drop or related power loss.
Courtesy: Over Voltage Protection Circuit for Automotive Load Dump
The LMV431AIMF (D1) adaptable reference works best for this situation just because it allows for an inexpensive means to ascertain a meticulous trip point and monitor optimal temperature accuracy which becomes quite difficult with a zener diode or likewise using other alternative options (1% for the A version, 0.5% for the B version).
For preserving this accuracy and reliability, resistors R1 and R2 is selected to be 1% tolerance or a still better may be recommended.
Variable reference voltages can be usually wrongly contemplated. Take for instance: "What’s that third wire terminating from that diode?"
You may find numerous types of variable voltage references. Different possessing different in-built set voltage while others with an alternate current direction polarity.
All of them can be identified with a couple of fundamental (and quite significant) stages: A temperature regulated, accurate band gap voltage reference, along with a gain error amplifier (incorporated as as a comparator in the discussed circuit).
Majority of the parts exhibit uni-poIar results by incorporating an open collector or emitter. Figure 2 indicates conceptually what may be expected inside Texas Instruments LMV431AIMF.
The input voltage is checked and controlled by the LMV431 with the aid of voltage divider R1 and R2. The circuit detailed in Figure 1 is configured to activate at 19.2V although an arbitrary cut of level could be opted which may be figured out using the following equations:
Vtrip = 1.24 x (R1 + R2 / R1)
R2 = R1(Vtrip/1.24 - 1)
The output of the LMV431 brings down as soon as the set reference pin is detected to be above 1.24V. The cathode of an LMV431 is capable to bring down to a saturation level of approximately 1.2V.
The mentioned level may be just enough to switch Q2 off. Q2 was predominantly hand picked to carry an elevated gate threshold (> 1.3V). Its not recommended to use a substitution for Q2 without considering this into account.
The chip operating conditions for D1, Q2, and Q1 are indicated in Table 1 for the condition involving of a 19.2V cut of point.
The circuits operating condition is detailed in Figure 3. The cut of level can be expected to be approximately in the 2.7V to GOV vicinity. Below about 2.7V the circuit may be seen transiting to the off situation.
The reason being the absence of sufficient input voltage to level up the gate to source thresholds of Q1 and Q2.
While its in the off state, the circuit offers around 42 kQ to the input (off status quiescent load). Zener diodes D2 and D3 are crucial for restricting the over shooting gate to source voltages as expressed by Q, and Q2 (which may not be allowed to go beyond 20V).
D3 likewise inhibits the cathode of D, from shooting above its specified limit of of 35V. Resistor Rd assures a compromised bias to Q2 so that it can fulfill Q2’s drain leakage in the off condition.
Its important to watch the body diode in Q, it implies that it carries no safeguarding to the load for wrongly connected battery (opposite polarity input voltages).
To be able to safeguard the condition of a wrong battery polarity, it may be advisable to incorporate a blocking diode or an reinforced alternate (one behind the other) PFET is may be also required.
The circuit can be seen attributed to actuate instantly although reestablish the conditions rather sluggishly. Capacitor C, exhibits quick discharging to negative via the LMV431 in an even of an over voltage is sensing.
As soon as the situation restores to normal, reconnection is slightly held up by the R3-C1 time delay variables.
A significant number of loads (that may be regulators) employ substantial input capacitors which allow time delay for the cut-off circuit to work out by inhibiting the transient slew rate.
The working pattern of the standard transient and the available capacitance become responsible fix the intended delay response time.
The shut off implementation from the proposed Over Voltage Protection Circuit for Automotive Load Dump takes place in approximately twelve Sec. The expected highest transient rise periods are constrained in a balanced level to the mentioned periods by C(load).
This circuit was verified with a C(load) of 1 pF. Larger load is may be tried and is okay considering rapid surging, reduced source impedance transients are to be present.
Introduction
Transient or repetitive over voltage circumstances that defeat an IC‘s absolute highest voltage spec may possibly irreversibly harm a device.
The necessity for over voltage safety is notably prevalent in automobile 12V and 24V designs in which peak "load dump" transients is usually as very high as GOV. Certain load safeguarding strategies shunt input transient to ground through devices similar to avalanche diodes and MOVs.
The difficulty with the shunt method is that a great deal of power could possibly end up being processed.
Shunt techniques are usually undesirable should there be an obligation to render continual protection throughout an over voltage situation (as transpires with dual battery).
The Circuit
The Over Voltage Protection Circuit for Automotive Load Dump shown in Figure 1 is a perfect series-disconnect or series cut-of circuit which has been built to safeguard a switching regulator load that possessed an optimum input voltage of 24V.
The circuit is intended from economical discrete devices and makes use of a single Texas Instruments LMV431AIMF.
Given that this circuit employs a PFET pass device (Q1), there may be a marginal forward voltage drop or related power loss.
 |
| Figure.1 |
Courtesy: Over Voltage Protection Circuit for Automotive Load Dump
The LMV431AIMF (D1) adaptable reference works best for this situation just because it allows for an inexpensive means to ascertain a meticulous trip point and monitor optimal temperature accuracy which becomes quite difficult with a zener diode or likewise using other alternative options (1% for the A version, 0.5% for the B version).
For preserving this accuracy and reliability, resistors R1 and R2 is selected to be 1% tolerance or a still better may be recommended.
Variable reference voltages can be usually wrongly contemplated. Take for instance: "What’s that third wire terminating from that diode?"
You may find numerous types of variable voltage references. Different possessing different in-built set voltage while others with an alternate current direction polarity.
All of them can be identified with a couple of fundamental (and quite significant) stages: A temperature regulated, accurate band gap voltage reference, along with a gain error amplifier (incorporated as as a comparator in the discussed circuit).
Majority of the parts exhibit uni-poIar results by incorporating an open collector or emitter. Figure 2 indicates conceptually what may be expected inside Texas Instruments LMV431AIMF.
The input voltage is checked and controlled by the LMV431 with the aid of voltage divider R1 and R2. The circuit detailed in Figure 1 is configured to activate at 19.2V although an arbitrary cut of level could be opted which may be figured out using the following equations:
Vtrip = 1.24 x (R1 + R2 / R1)
R2 = R1(Vtrip/1.24 - 1)
The output of the LMV431 brings down as soon as the set reference pin is detected to be above 1.24V. The cathode of an LMV431 is capable to bring down to a saturation level of approximately 1.2V.
The mentioned level may be just enough to switch Q2 off. Q2 was predominantly hand picked to carry an elevated gate threshold (> 1.3V). Its not recommended to use a substitution for Q2 without considering this into account.
The chip operating conditions for D1, Q2, and Q1 are indicated in Table 1 for the condition involving of a 19.2V cut of point.
The circuits operating condition is detailed in Figure 3. The cut of level can be expected to be approximately in the 2.7V to GOV vicinity. Below about 2.7V the circuit may be seen transiting to the off situation.
The reason being the absence of sufficient input voltage to level up the gate to source thresholds of Q1 and Q2.
While its in the off state, the circuit offers around 42 kQ to the input (off status quiescent load). Zener diodes D2 and D3 are crucial for restricting the over shooting gate to source voltages as expressed by Q, and Q2 (which may not be allowed to go beyond 20V).
D3 likewise inhibits the cathode of D, from shooting above its specified limit of of 35V. Resistor Rd assures a compromised bias to Q2 so that it can fulfill Q2’s drain leakage in the off condition.
Its important to watch the body diode in Q, it implies that it carries no safeguarding to the load for wrongly connected battery (opposite polarity input voltages).
To be able to safeguard the condition of a wrong battery polarity, it may be advisable to incorporate a blocking diode or an reinforced alternate (one behind the other) PFET is may be also required.
The circuit can be seen attributed to actuate instantly although reestablish the conditions rather sluggishly. Capacitor C, exhibits quick discharging to negative via the LMV431 in an even of an over voltage is sensing.
As soon as the situation restores to normal, reconnection is slightly held up by the R3-C1 time delay variables.
A significant number of loads (that may be regulators) employ substantial input capacitors which allow time delay for the cut-off circuit to work out by inhibiting the transient slew rate.
The working pattern of the standard transient and the available capacitance become responsible fix the intended delay response time.
The shut off implementation from the proposed Over Voltage Protection Circuit for Automotive Load Dump takes place in approximately twelve Sec. The expected highest transient rise periods are constrained in a balanced level to the mentioned periods by C(load).
This circuit was verified with a C(load) of 1 pF. Larger load is may be tried and is okay considering rapid surging, reduced source impedance transients are to be present.
Available link for download
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