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Old 08-05-2014, 17:00   #1
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Mastervolt Whisper 3,5 - getting to the diodes

My 2008 Mastervolt Whisper 3,5 is running at 62 Hz and 3670 RPM but only producing 97 Volts AC. It therefore triggers the low AC voltage shutdown. I have isolated the cause to diode failure on the rotor. Does anyone have a workshop manual that describes the disassembly process to get to these diodes for replacement?

I have the users manual, installation manual, parts manual, and Kubota engine manual - but none of these cover the generator in any detail.

I believe the correct manual is part number 05-02-00170, or I have also seen it written as 050200170 and 50200170

Another question - does anyone know what the spec is for these diodes as the new Whisperpower US representative does not stock them?

Thanks in advance for any advice and help.
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Old 13-05-2014, 05:11   #2
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Re: Mastervolt Whisper 3,5 - getting to the diodes

Update

I have proceeded without the workshop manual - and stripped away the housing and all the cabling from the generator end of the assembly - only to find that the way to access the rotor is to split the assembly in the middle.

I would be very grateful for any advice from anyone who has done this with a Mastervolt product - or now they are called Whisperpower - the division having been sold by Mastervolt in 2009.........
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Old 13-05-2014, 09:31   #3
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Re: Mastervolt Whisper 3,5 - getting to the diodes

Get in contact with Sure Marine they are the Master in the NW with MasterVolt, they have a generator specific department with real techs that are factory trained.

Lloyd

Quote:
Originally Posted by peterdev View Post
Update

I have proceeded without the workshop manual - and stripped away the housing and all the cabling from the generator end of the assembly - only to find that the way to access the rotor is to split the assembly in the middle.

I would be very grateful for any advice from anyone who has done this with a Mastervolt product - or now they are called Whisperpower - the division having been sold by Mastervolt in 2009.........
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Old 13-05-2014, 10:11   #4
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Re: Mastervolt Whisper 3,5 - getting to the diodes

Specs for diodes,capacitor, and varistor

1 Varistor (420V);
2 EMC capacitors (4,7nF - 630V);
3 Diodes (25A - 1200V).

5.3 SPECIAL PROCEDURES ALTERNATOR
5.3.1 Residual voltage check / excitation
procedure
When residual magnetism disappears there is no residual
voltage. Residual magnetism can disappear after the
generating set being out of service for a long period or
suffered a short circuit. This can be solved by charging the
capacitor ("flashing") independently with a small 9 Volt
battery. This can be done while the engine is stationary
and the wiring is connected.
If the generating set battery is used for
flashing one must take care. A short circuit
can cause heavy sparking, fire and injuries
Figure 14
When flashing does not bring back voltage, the
capacitor(s) should be renewed. When this does not help,
the rotating rectifier diodes should be tested and a winding
resistant test should be executed.
5.3.2 Testing rotary rectifier diodes
The diodes in the rotor can be checked with a multimeter.
When both diodes are faulty the alternator will not
generate any voltage. When only one diode is faulty the
alternator will generate about half the normal voltage. The
flexible lead connected to the diode should be
disconnected at the terminal end, and the forward and
reverse resistance checked. A healthy diode will indicate a
very high resistance (infinity) in the reverse direction, and
a low resistance in the forward direction. A faulty diode will
give a full deflection reading in both directions with the test
meter on the 10,000 ohms scale, or an infinity reading in
both directions. The problem can also be in a faulty surge
suppressor which is a metal-oxide varistor connected
across the diodes, or the ESD capacitor. Replace the
diodes, the suppressors and the capacitors.
Figure 15
5.3.3 Winding resistant values
If after establishing and correcting any fault on the
capacitor and diodes output is still low when separately
excited, then the main rotor, stator and exciter stator
winding resistance should be checked as the fault must be
in one of these windings. The respective leads must be
disconnected before taking the readings.
Resistance values should be within 10% of the values
given in the table below:
Resistance 50Hz
• Resistance both main stator windings
in series
1.2 Ohm
• Resistance both rotor windings 2.1 Ohm
• Resistance battery charger winding 0.15 Ohm
• Resistance exciter stator winding 2.4 Ohm
5.3.4 Meggering
One can try to measure resistance between the housing
and the windings with a multimeter which should read
infinity. When readings are infinity but a fault is suspected
one can do a high voltage resistance test (MEGGERING)
This procedure should be carried out by an expert
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Old 13-05-2014, 17:59   #5
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Re: Mastervolt Whisper 3,5 - getting to the diodes

Thanks - FlyingCloud1937

I will call Sure Marine in the morning and ask them for guidance.

It seems that the diode on the rotor may have failed as the voltage is low at 97 volts.

The real challenge is to get to the rotor without a workshop manual - which does not seem to be available.

What I have so far not been able to understand is whether this low voltage is due to a capacitor failure or a diode failure - so will def ask the experts at Sure Marine. Or maybe a winding failure - but this seems less likely as they are quite heavy copper wire.

More to follow......
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Old 16-05-2014, 21:50   #6
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I have a friend with one of these units and has to replace the caps every couple of years in cruising use with a large inverter / charger. The voltage drops off as you describe. Thus far new caps have always fixed that problem.

If the voltage gets too low the self protect circuit will shut down the generator. The last error is often low oil pressure which confuses issues.

Good luck.
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Old 18-05-2014, 07:00   #7
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Re: Mastervolt Whisper 3,5 - getting to the diodes

@Botanybay - thanks for the advice - now in retrospect - having the whole generator completely disassembled - if one looks at the active components it can only be diode on the rotor, or the capacitor in the exciter winding. On the passive side - it can be any of the windings - but these are really heavy gauge copper - so hopefully the inherent design of the generator is such that these are never overloaded for their size.

After much frustration - I finally have access to the rotor and diode - there is only one. I took it out of circuit and tested it to be open circuit in both directions. I have ordered a new diode, and will get everything back together next week. I have also ordered new capacitors - this generator has a 30uF and a 2uF connected in parallel - so will test the old and new when it is running again.

If anyone needs to go through this disassemble process - please contact me as I can try to guide you through how to get this accomplished. I think the workshop manuals are not available as there are a few different generations of this product in the field, and maybe the documentation has not been able to keep up.

More to follow as I assemble.....
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Old 18-05-2014, 11:56   #8
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Please do write it up! I am sure I will have to dig into his generator eventually for this one!
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Old 21-06-2014, 22:09   #9
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Re: Mastervolt Whisper 3,5 - getting to the diodes

Quote:
Originally Posted by peterdev View Post
My 2008 Mastervolt Whisper 3,5 is running at 62 Hz and 3670 RPM but only producing 97 Volts AC. It therefore triggers the low AC voltage shutdown..
I have an Entec 4.2kva single cyclinder farymann engine 3,600 rpm. Idle voltage is 98volts with 60hz. Found tips on CF, replaced the capacitors which was broken with a new cap 20uF for usd 6 a piece. The idle voltage went up to 125volts. Under load came down to 115volts.

I was told there are 2 types of capacitors for motor. One is for starting and the other for running.

I am not an engineer so just reporting what I have done.
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Old 14-11-2017, 07:40   #10
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Re: Mastervolt Whisper 3,5 - getting to the diodes

Quote:
Originally Posted by peterdev View Post
If anyone needs to go through this disassemble process - please contact me as I can try to guide you through how to get this accomplished. I think the workshop manuals are not available as there are a few different generations of this product in the field, and maybe the documentation has not been able to keep up.
More to follow as I assemble.....
Hi Peterdev,
I have the same problem, I have to replace the diode . could you send me more information about the procedure to disassemble the rotor? some photo?

Best Regards,

Dimit
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