Lenze VFD resistor fault - Page 1
Forum section: electronics / repair

author: 97paul
author_rank: Contributor
timestamp: April 15, 2025, 08:45:31 pm
content: Hello everyone, I have a problem with a frequency converter that is blowing the charging resistor for the intermediate circuit.I replaced the charging resistor and V213 (the transistor next to the transformer that generates primary voltage for the transformer; it had a short circuit).I replaced those parts, as well as two metal-paper capacitors and all electrolytic capacitors except the intermediate circuit capacitors. I tested the input rectifier with 1000V DC. The IGBT module is OK. I also checked the relay.The frequency converter was then slowly powered up in single-phase mode using a variable transformer. The relay switched on correctly when the minimum intermediate circuit voltage was reached. The function test with the motor check worked without any problems.When I connected it to three phases today, the charging resistor immediately burned out again.Does anyone know what else could be causing this?

author: 97paul
author_rank: Contributor
timestamp: April 16, 2025, 05:10:17 pm
content: Does nobody have an idea?

author: croaker
author_rank: Contributor
timestamp: April 16, 2025, 06:48:57 pm
content: Hi,Did you replace the charging resistor with a similar one? Did the transistor burn out again too? What is the power of the VFD?

author: 97paul
author_rank: Contributor
timestamp: April 16, 2025, 09:44:11 pm
content: I replaced the charging resistor with an original one. The BU2508AW transistor was short-circuiting again. The transistor failed first and then destroyed the charging resistor. 3-phase 400V 3KW

author: croaker
author_rank: Contributor
timestamp: April 16, 2025, 10:21:14 pm
content: There was no such VFD under repair, but they are all similar.The power supply operates from a ~540V DC bus, the voltage reserve of this transistor is small. Therefore it is necessary to check the entire transistor binding and the PWM controller.

author: elektryk
author_rank: Regular Contributor
timestamp: April 17, 2025, 05:13:31 am
content: Quote from: 97paul on April 16, 2025, 09:44:11 pmIts quite old transistor, are you sure that you've got a genuine one?

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 07:11:36 am
content: https://www.ebay.de/itm/401576322288?mkcid=16&mkevt=1&mkrid=707-127634-2357-0&ssspo=HH4pkJt-Tfq&sssrc=4429486&ssuid=k7dVCtLATrq&var=&widget_ver=artemis&media=COPY

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: April 17, 2025, 08:59:18 am
content: Quote from: elektryk on April 17, 2025, 05:13:31 am(Laser?) marking looks pretty new^^ on the unit OP bought.Same part,5 times cheaperSure that for such a 3 phase 400 VAC VFD, elektryks' point of view makes sense : it would be wise to check the Vceo breakdown voltage of the replacement part.As hfe is really low (min value 4), there must be a base driver upstream. Everything's healthy there ?Tells us more about the transformer downstream of this power transistor. Is it the one with the yellow tape insulation ?In the affirmative, did youringit ?Is the broken hybrid resistor in series with the primary of the transformer ?If not yet done, replace unconditionally all of the small size electrolytics caps.

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 04:16:45 pm
content: I just checked again and found out that this type of transistor was often used in tube TVs. When they were no longer manufactured, these transistors were sold very cheaply. So I think it's original.I replaced all the electrolytic capacitors.The strange thing is that it worked perfectly on a single-phase variable transformer at around 380V. I slowly increased the voltage. So it can't be the control circuit, right?The X2 capacitors have bad values. They should be 150nF. They only have 50nF. But that can't be the cause, can it? They're there to suppress interference on the three phases.I'm attaching a poorly designed circuit diagram of mine.

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 04:18:29 pm
content: Circuit

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 04:19:40 pm
content: Circuit

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: April 17, 2025, 05:26:49 pm
content: OK for the circuit.After flipping my monitor upside-down, I finally understood that thedefective transistor V213 swiches the primary of the ferrite transformerT203.If the transistor did not survive, the first culprits are a defective T213 or HYB201 malfunction. Check each part of the latter (or replace the whole hybrid if available) and ring T203, as already suggested.Can you complete the schematic on the secondary side of T213 ?What is the nominal voltage ofC46C116 and C48 ?Is there an SMD part missing on the left ofC46C116 and C48 ?I could not find the defective HYB1 power resistor on your schematic.

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 05:44:22 pm
content: C116 C48 50V 100uF

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 05:48:10 pm
content: I can't imagine that the transformer is defective. The frequency converter was fully functional single-phase.

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 05:52:00 pm
content: The charging resistor is connected in series between the negative and intermediate circuit capacitors.

author: 97paul
author_rank: Contributor
timestamp: April 17, 2025, 06:10:24 pm
content: I have exactly the same frequency converter. I'll take it apart tomorrow and compare it with this one.

author: croaker
author_rank: Contributor
timestamp: April 17, 2025, 11:29:36 pm
content: If the transistor is burnt out, everything needs to be checked again before switching it on again.The transformer is most likely OK. You need to check the capacity of the capacitors in the snubber circuit. This is the circuit that suppresses high-voltage surges on the transistor collector.Next, you need to check the PWM chip (what chip is installed, look datasheet), it has its own power supply chain, it usually contains an electrolytic capacitor, which loses capacity.You also need to check the relay that short-circuits the DC bus charge resistor. After such disasters, its contacts can burn out.The first switch-on after repair is also at a reduced voltage, as you already did.Good night.Sorry for my "Google English".

author: 97paul
author_rank: Contributor
timestamp: April 18, 2025, 03:08:05 pm
content: I checked the entire HYB201 circuit board today. I couldn't find any defective components.I'll try desoldering the transformer. Can you also test a transformer with a growler?

author: 97paul
author_rank: Contributor
timestamp: April 18, 2025, 03:11:08 pm
content: The snubber diodes are all fine and the 2 ceramic capacitors are also fine.

author: 97paul
author_rank: Contributor
timestamp: April 18, 2025, 03:15:31 pm
content: There's no PWM chip. Control is handled by the HYB201.